Tube Amp Spa

THIS IS THE SHERMAN WATERING HOLE

WHERE TECHNICAL AUDIO LOVERS JUST HANG OUT

AND READ ABOUT COOL STUFF RELATED TO ME

MY HOBBY AND MY LEGACY YEARS

BUILT ON CUTS, SWEAT & A FEW SHOCKS

IT GOES SOMETHING LIKE THIS

MY MEMORY, AS MUCH AS I CAN MAKE IT PRODUCE

In the late 80's to the early 2000's, I must confess,

I was subscribed to both Stereophile & The Absolute Sound.

Now, I am just a Jazziz subscriber, and own a remarkable

Jazziz CD Collection with wonderful new artists

that often Shazam, has no clue about, Nice!

AI is powerful, until it cannot even produce

an Output for a totally unknown Input.

If AI does not have it in their database, AI will be clueless.

The algorithms needed for AI to calculate a prediction of

what it is processing may eventually be a reality.

But we are A LONG ROAD away from that.

Bob Marley would have sang:

"Don't you fear AI technology, for none of them can stop the Time"

I read these Audio Magazines, cover to cover

with a Tea/Beer/Wine Light Classical Music

Audio publications, taught about who were the Masters who made

today's Audio Scene possible.

I honor here a few of the visionaries by their names;

David Hafler

Ed Laurent

 Stan Warren

Nelson Pass

Saul Marantz

Walt Jung

Sidney Harman

Bernard Kardon

Avery Fisher

H.H. Scott

Stuart Hegeman, and many, many more... 

THE END OF THE DYNACO AGE

In the 1980's Dynaco, by then PANOR CORP

and Panor had just re-released the Stereo 70 in the Late 90's

and a Version II in 2004, to mixed reviews.

Probably using the wrong Speakers for the review (just my hunch).

Still, these Dynaco Tube amps were $995-1100 or more, even back then "Ouch"

I was a young Engineer making mid 50's and that was a chunk of Cash,

I just did not have to spend off on a luxury.

AUDIO MAGAZINE HEROES

My heroes in Audio publications in my early Audio journey.

Most of these amazing people, are already with Harvey listening

to some 300H Tubes (H = Heaven).

J. Gordon-Holt

Corey Greenberg

Harvey Rosenberg

Harry Pearson

Charlie Kittleson

and a few more....

MY FIRST SERIOUS AUDIO PURCHASE

My Wife and I drove to Roanoke VA as we were invited to a Klipsch Factory presentation

of the Klipsch Sub-Sat System. Back in 1991 Home Theater was in full Bloom back then.

I did finance an ADCOM GTP-400/GFA-535 at Audiotronics. That evening I drove Home to Lynchburg

with two Boxes of Goodies and a loan from AVCO, that was paid in less than 1 year.

That Credit allowed me to borrow more later for an Emergency. I learned that

Good Credit is important for recent College Graduates.

ADCOM was at that time, the HOT Stereophile Class D brand.

It was entry level Hi-Fi, for budget conscious Music lovers.

Cary Audio ads were the Beverly Hills of Audio, as still is McIntosh.

The Cary Audio Lady, listening in bliss, to DHT TUBES, what?

Eventually, I would order a copy of "The Mullard Book"

and the seeds that sprouted into ShermanAudio were planted.

 EL-34 Push Pull plots of Output Impedance, Power vs. Frequency Response

It was incredible information for an Me as an EE.

I now fully understood how a Tube Push Pull amplifier

Output Transformer section works.

I never took Tubes in College, they were already obsolete.

Tubes are "Non-Complementary" no NPN/PNP with Tubes.

I read about optimizing EL-34's

creating clean Power, through an Output Transformer.

A pair of Mullard EL-34's provided 20W of Peak Power.

I noticed the EF86, a midget Pentode?

The EF86 taught me to be careful with Tube Substitution Books.

The EF86 was listed as an EL-84 sub, hence I made

my First Monoblocks with EL-84 in the input, worked, but sounded

BOLD, BRASH, OVER THE TOP

Learning and Education are hard things, but the energy is worth it.

This Mullard 5-20 amp was "Low distortion" for 1959.

So, I decided to create my own Mullard 5-20 Monoblocks from parts.

The Mullard book presented the 5-20 and all of their designs like

Engineers, for Engineers. I am always accused of talking too

much detail, of being over the top when I answer questions.

Well I do not just answer questions, I inform and educate.

A skill that I use in Public Speaking with a high degree of success.

WHEN DID THE MULLARD'S FIRST SOUND?

This started back in Mid 1996.

They 5-20's first sounded in the Summer of '96 at 3am.

I had about 5 Miller Light's on me and when I threw the switch

I finally got music with no motor-boating.

Music that made my heart skip a beat and my Hairs stand up, goosebumps.

No recent experience can surpass the Joy of hearing your FIRST AMP sound.

I remember going back to the bedroom at 4am and whispering to my wife

THEY WORKED

It was Spring of 96 and I was already infested with Tube Audio.

Now these 5-20 Amps, took 25 years to debug and perfect, no joke.

The Mullard 5-20's are not an easy build, for non-intuitive reasons.

And following the specs for the Power Transformer and Choke in the Manual

taught me a serious lesson, they just were not relevant 60 years later.

The Mains Transformer was specified as 400-0-400 Volts, a huge mistake

when using modern, Lower Iron and Copper Loss Hammond Transformers.

The correct Hammond is in my Website and has 115/125V AC Switching.

Today's Mains transformers are more efficient and wound to tighter tolerances.

Hence they will perform the Vintage Mains types.

But... old Output Transformers, it is here where modern types

might not sound as good. They may measure better, but the music seems

to lose some air, they do not breathe like a Freed, Fisher, Scott, Knight...

So in the Mullard Book, the level of Rectified DC Voltage was sheer suicide for the EL34's.

Aggravated by a 115V Primary, I struggled to understand while my EL-34 Red Plates

screamed and died and early $death$, so did my bank account.

Note that 5-20's are Plate Voltage sensitive as are most Cathode Biased Power Amps.

After many Red Plates, and Worn Quads of premium EL-34's

I finally perfected these Amplifiers in 2018-2019 in Ashburm VA.

The 5-20's are very nice, especially with a quiet Preamp.

The 5-20's are dead quiet now and Musical.

What they lack in inner detail, they have in midrange bloom.

It has to be partly the EL-34 sound, each Pentode can do

some things well, and the EL-34 is a Midrange King.

I would state the 5-20's Sound is clear, unlike what tubes do.

Fast, Present and Harmonically Rich, but never bloated in the Bass.

I have all of the parts defined now, so if You decide to build

a pair of 5-20's, so You can avoid all of My pitfalls with

none of the hassles I faced, I suffered the build so You don't have to.

The full 5-20 story is in my Website.

For every Amp, Preamp, Speaker and Test Jig I have created

a story unfolds in my Journey and Logs, here are those stories.

Sit back and enjoy the electrons flowing inside of a Glass Vacuum.

TUBE NIRVANA?

Ultimately, my final destination is Tube Nirvana so BTW

I have been close, but not YET arrived.

I think my closest to Nirvana, was a pair of

Jolida 211 - 200 Watt/Ch Monoblocks

A pair of Omnidirectional MB-Quart Speakers.

I was in the lobby of Tube Heaven, but the door was still locked.

This happened at the Capital Audio Fest, Sheraton - Silver Spring MD.

Sometime back in 2011 maybe? I have to check my Video Camera.

Now that was knocking on Heaven's door

I took a video of this, so will post here soon.

A DIY TUBE HOBBY IS NOT AN EASY STREET

IT IS THE HOOD OF AUDIO.

AS ALL GOOD THINGS IN LIFE ARE NOT EASY.

THE COSTS HAVE NOW TRIPLED FROM THE 90'S

AND LOTS OF WHAT WAS ONCE AVAILABLE IS

NOW OUT OF PRODUCTION, EXCEPT THE TUBES

THESE ARE STILL ORDERABLE.

GETTING PARTS

IT TAKES MORE EFFORT NOW TO HUNT FOR PARTS

THAN TO BUY FOREIGN CHINESE TUBE AMPS

EBAY IS STILL AWESOME

BUT GREEDY PEOPLE SELL THEIR GREED, NOT ITEMS.

AND THE FREE SHIPPING THAT CHINA GETS,

TO SEND US STUFF, MAKES CHINA THE GO-TO FOR PARTS

AMAZON IS NOT FAR BEHIND EITHER, THEY DELIVER!

IF YOU EVER ASKED YOURSELF, WHY IT COSTS MORE

TO MAIL A PACKAGE TO THE NEXT U.S. TOWN,

WHILE A LARGE BOX FROM BEIJING COSTS THE SENDER CLOSE TO NOTHING

THANK THE INTERNATIONAL POSTAL UNION AND OUR

TAX DOLLARS, AS WE ARE NOT ONLY PAYING FOR THIS,

WE ALSO PAY FOR WARS, NATO, ETC. "UNITED WE FUND" IS OUR NEW MOTTO.

THIS ARTICLE EXPLAINS THE CHINA ADVANTAGE

AS A SUPPOSED 'TRANSITIONAL COUNTRY'

TRANSITION TO WHERE? TAIWAN?

https://www.scmp.com/news/china/diplomacy/article/2169144/chinas-cheap-shipping-advantage-explained

MY TROUBLESHOOTING TIPS

On "Close Encounters" of the "Humming" kind

HOW TO DIAGNOSE THE UBIQUITOUS "UN-MOLESTED" CLASSIC EBay TUBE AMP

AND WHY USING 60 YEAR OLD TUBE AMPS IN 100% ORIGINAL STATE IS DOGMATICALLY FOOLISH

 YES YOU CAN ASSEMBLE A CURRENT LIMITER 

OR MAYBE ACQUIRE A USEFUL VARIAC

PLEASE DON'T JUST PLUG THAT OLD EBAY AMP INTO THE WALL

HOPE AND AUDIO DOGMA ARE NOT SAFETY PROTOCOLS

ONE RISKS BLOWING UP SOMETHING OF IRREPLACEABLE VALUE

FACTORY ORIGINAL OUTPUT TRANSFORMERS ARE "TREASURES"

YOU NEED TO PRESERVE AND PROTECT THEM

LOSING A POWER TRANSFORMER, THAT CAN BE REPLACED OR RE-WOUND

BUT FACTORY ORIGINAL OUTPUT TRANSFORMERS CANNOT!

YES OUTPUT TRANSFORMEFRS CAN BE RE-WOUND

BUT YOU CANNOT DUPLICATE THE ORIGINAL WIND

WINDING TECHNIQUES ARE NOW ALMOST TOTALY LOST IN TIME

AND THE SOUND OF A TUBE AMP IS DEFINED BY THE OUTPUT TRANSFORMERS

NOT THE TUBES, IMAGINE WHAT YOU MAY.

ROLLING POWER TUBES IS 20% OF THE TUBE AMP CHARACTER

THE REST IS IN THE OUTPUT TRANSFORMERS

LAMP CURRENT LIMITER

(BUY SPARE 75 TO 100 WATT INCANDESCENT BULBS, BEFORE THE GOVERNMENT BANS THEM)

STEP1: MEASURE AND TEST ALL TUBES, REPLACE WITH GOOD TUBES, THIS IS CRITICAL TO START WITH GOOD TUBES. IF YOU DON'T OWN A TUBE TESTER THEN CONSIDER RETURNING TO SOLID STATE, NO HARD FEELINGS, JUST THE TRUTH.

STEP2: REPLACE FUSE WITH CORRECT VALUE, THIS IS CRITICAL ALSO. USUALLY YOU WILL FIND THE WRONG FUSE OR A BYPASS.

STEP3: REPLACE ALL ELECTROLYTIC CAPACITORS WITH FRESH NEW STOCK. FORGET TALES OF REFORMING CAPACITORS, REFORMING OLD ELECTROLYTICS IS LIKE REFORMING CAREER CRIMINALS, THEY JUST DON'T REFORM.

STEP4: MEASURE/REPLACE ALL OUT OF TOLERANCE VOLTAGE DROPPING RESISTORS IN THE POWER SUPPLY. JUST AS WELL REPLACE ALL CATHODE, GRID AND PLATE RESISTORS WITH FRESH 2% TYPES, DON'T BE CHEAP, SPEND THE $15-20 DOLLARS

STEP5: REPLACE SIGNAL COUPLING CAPACITORS WITH FRESH NEW CAPS, DON'T RISK LEAKY CAPACITORS, ORANGE DROPS ARE FINE.

COUPLING CAPS, CAN DESTROY NEW TUBES IN A FEW WEEKS/MONTHS. THOSE 50+ YEAR OLD CAPACITORS

AND CARBON COMP RESISTORS ARE BEYOND USEFUL SERVICE LIFE.

BREATHE NEW LIFE INTO OLD TUBE AMPS

DON'T ACCEPT THE MUFFLED, ROLLED-OFF, FUZZY SOUND PEOPLE ASSOCIATE WITH TUBES.

BRAND NEW POTENTIOMETERS ALDO MAKE A DRAMATIC DIFFERENCE, AND ONE WOULD NEVER KNOW.....

WOULD YOU KEEP YOUR 20 YEAR OLD SHOCK ABSORBERS, SO YOUR CAR WOULD REMAIN "ALL ORIGINAL"?

STEP6: CONNECT TO A PAIR OF CHEAP SPEAKERS, IMPORTANT SO YOU CAN TURN OFF THE POWER IF THE AMP MAKES WEIRD NOISES

STEP7: CONNECT A RELIABLE SOURCE TO THE INPUT, THEN SET THE VOLUME AT ZERO AND ALL AMP CONTROLS TO CENTER POSITIONS

STEP8: POWER ON AMP - PRESS PLAY ON YOUR SOURCE - THEN AFTER 5 TO 8 SECONDS, START TO SLOWLY INCREASE AMP/SOURCE VOLUME, IF AMP PLAYS WITH NO HUM/NOISES GREAT.....

LEAVE IT ON FOR A BIT AND LOOK FOR ANY RED PLATES, SMELLS, ETC.

IF YOUR AMP HUMS, POWER OFF. TIME TO TROUBLESHOOT THE HUM. IF IT SOUNDS LIKE A BUZZ ITS 120HZ HUM

IF IT SOUNDS LIKE THE WORLD IS ENDING THAT IS 60 HZ HUM, MORE SERIOUS.

IF THE AMP BUZZES...

This Buzz is 120 Hz Ripple, and this is not all that bad, and hope is knocking at the door.

The Buzz can also be Heater to Cathode Leakage noise and this is more like a hard Buzz, and worst case 60 Hz Hum.

AC Filaments operate a 60 Hz (or DC).

STEP9: IF THE AMP PLAYS WELL FOR 15 MINUTES, ADJUST THE BIAS (IF BIAS IS ADJUSTABLE) THEN LOOK FOR RED PLATES ON POWER TUBES AGAIN IN A DARK ROOM.

YOU MAY NOW HAVE AN AMP TO BE MONITORED FOR A FEW DAYS

NEVER LEAVE A TUBE AMP ON AT HOME "ALONE", TURN IT OFF

THE SUBJECT OF AMP AND PREAMP NOISE, BUZZ & HUM

Now I want to get this one off my chest, silent idling classic Tube Amps are a Myth.

All classic tube amps make some type of noise when idle, but the goal, to address and reduce these noises.

Tubes are great at amplifying the last minute signal or unwanted noise.

So when your speakers are buzzing or humming, check your sources.

More often than not those small Streaming Boxes will send a noisy signal to that

first Vacuum Tube in the amplification gain stage, so try to isolate this first before blaming your Tube Preamp or Amplifier(s).

60 HZ HUM? IS THERE SUCH A THING? YES! BUT NOT WHAT YOU BELIEVE...

I hear this term all across YouTUBE Channels, and really wonder if anyone has ever really heard 60 Hz Hum?

Highly unlikely....

My friends, 60 Hz Hum is a catastrophic noise, if you ever hear it, the next thing you want to DO IS PUSH the OFF switch.

60 Hz Hum is a rare occurrence something is off in the Power Supply or a AC Power Like leakage into the DC Supply.

The Law of Superposition allows both AC and DC to coexist on the same wire, node, pin, etc.

60 Hz Hum is when Rectifiers may fail, Filter Caps conduct DC current

Or a less than ideal Vacuum Tube might be leaking 60 Hz; from Heater to Cathode

60 Hz Hum is what you hear when AC Power line 60 Hz (or 50 Hz) sinusoidal alternating current and voltage

from the Transformer Secondary (or far more sinister the Primary) makes it to your Woofer Cone.

60 Hz is a fault when leaking or passing through AC made it to the DC Power Supply rail

It somehow is sneaking past the Power Supply rectifier and/or filtering sections, or both.

60 Hz Hum this will make it to your Woofers and WOW.

They do shake, and sometimes, the Voice Coil melts, Ouch.

60 Hz is a low, very low frequency, it is not a Buzz, but a very deep HUM.

Imagine that the low string on a Bass Guitar goes down to 41 Hz... pluck this and listen.

Now think about a frequency some 20 Hz above that, and you can find this on the Bass guitar fret board

by examining the chart below;

On the Bass Guitar E string, go to the 6th Fret and that is 58 Hz, while the 7th Fret is 62 Hz.

In 50 Hz Countries that Bass Note is on the 3rd Fret on the E string at 49 Hz practically 50 Hz.

Pluck those and see if you hear a Buzzing Sound?

 So the next time YouTUBE Musicians or Buzzword slingers are in a studio or creating content,

complaining about their Single Coil Pickup 60 Hz Noise and their Tube Amps 60 Hz Hum... hummmmm.

60 Hz Hum is not a buzzing noise, it is not your Single Coil Guitar Pickups.

Single Coil Pickups are prone to amplifying Common Mode Noise and inductively couple to stray Electromagnetic fields.

So 99% of Musical Instrument Cables are Single Ended, not Balanced, prone to picking up garbage.

This is why a good Wireless Guitar Transmitter de-couples the instrument from the Amplifier

and hence protects from these kinds of things we refer to as Hum or a more accurate and correct Buzzzz...

60 Hz Hum is a defect somewhere in the Electronics, mostly from the Power Supply or even wiring mistakes.

It can also be due to improper, but well meaning introduction of a 3 prong AC Power Cord in a Classic Amplifier.

People hope that Grounding a 2 Prong Classic Amp with that 3rd Safety Ground bonded to the chassis

is a great upgrade.... not always, unless the DC Grounds are isolated from the Chassis... huh?

Therefore 60 Hz Hum is a Power Supply failure where the Rectifier Short Circuits,

the Filter Caps fail or there is a major malfunction of the Power Transformer or a Tube.

Some Plate and Filament Transformers do fail and this is pure 60 Hz madness, and also a shock safety issue.

What people miss-label 60 Hz Hum mostly "ripple" of 120 Hz Rectified DC.

Generally Hum can be created by induction between improperly routed wires, especially in DIY builds (I know).

If you don't know what a Rectifier or Rectification is, or does, what it means, read up.

A strong 120 Hz ripple is what we hear when the equipment is not properly DC Grounded

Or the Power Supply Filter Capacitors are struggling to do their job.

Yes aging Power Supply filter capacitors, these are toxic.

In fact Power Supply Buzz is far more common than you know.

The we then have a situation called a Ground Loop, especially with Turntables.

Tube Amps will ALWAYS have some residual 120 Hz ripple, it is almost impossible to extinguish.

As long as you cannot hear it from your listening chair, you are covered.

But it your Woofer vibrates, something if wrong. A light buzzing sound is normal for Vintage Tube Amps

and also Preamplifiers, where the Tubes may be past their prime. Hum can also come from bad New Tubes.

Believe Me I have had my share of Bad New Tubes and Hummy NOS Tubes.

Unless you own a Tube Tester that tests for Noise, the acid test is in the equipment.

Eliminating 100% of Buzz in Classis Old Tube Amps is a worthy but unattainable goal.

Unless you power your whole Tube Amp System from DC batteries.... you replace the Ripple with Battery noise...

120 Hz Buzz (Hum) happens with all kinds of Audio Gear and its not limited to just Amplifiers.

Preamplifiers also suffer from 120 Hz Hum (ripple) and it is very annoying.

Electric Guitars pick up 120 Hz ripple from their Cables and Amplifier and Pedals....

The solution here is to troubleshoot and isolate the culprit, there is no other way.

We can only reduce 120 Hz ripple, as every DC Power Supply always has some ripple.

The less ripple, the quieter the DC rail.

If you want to know more about Grounding, pick up a text and read.

Grounding is one of the most misunderstood topics in Electricity.

Just as people still to this day speak of 110 VAC, another misunderstanding.

Only experience and learning provide the basis for understanding.

CALLING 60 HZ HUM, 120HZ RIPPLE OR GROUND LOOP NOISE

IS LIKE CALLING APES, MONKEYS

No matter how many times we try, people still call Orangutan, Gorilla and Chimpanzee - Monkeys.

My answer here, open a Book and Read, swipe that iPhone and get your facts straight.

Don't rack up $200K in student loans, before you understand the fine print.

A College Degree, is what you make of it, while some Degrees opens Doors, others cannot.

A College Degree should be a version of what

You Love to do, but be very pragmatic.

Trades are a great alternative to a College Degree

Ask yourself the difficult questions, before signing a Government Student Loan.

If you love Marine Life, and have has a passion for it from Childhood, and have self educated

and participated in local Marine Biology related activities

Yes go for the Marine Biology or Oceanography Degree.

If you have never been to a Beach, imagine what Marine life is about, think again....

Also and unfortunately, College Degrees are mostly over priced

They are also "over sold" at Name Brand Universities & through Government Loan programs.

The Student Loan is nothing more than a "Weaponized" Monetary Instrument.

Government sponsored Student Loans are just like a Time Share contract.

It can end up like a Scam turned into a Government Monetary instrument for some.

NOBODY can guarantee a job, NOBODY.

Entitlement is not a skill......

If you ever heard of a Time Share, then the Student Loan weaponizes loans, like a Time Share does.

What do I study?

Just like betting on a Snail or a Rabbit in a race, today the STEM degree is the Rabbit.

It is a shame that today, Humanities do not pay bills or give a decent living

Even Teaching is a broken profession now, a crying shame.

The same de-humanization is progressing at an advanced pace...

rapidly escalating into Opioid and Alcohol addictions

How can any educated person think that Cocaine is safe?

I am dumbfounded by the level of ignorance of reality these days.

THIS MY FRIENDS IS AN TUTORIAL ON 60 HZ HUM

 AN EXAMPLE OF SLINGING BUZZWORDS

JUST LIKE 110VAC, ANOTHER MISNOMER BUZZWORD

EVEN ELECTRICAL ENGINEERS WITH DEGREES STILL UTTER 110VAC

WHY? THEY DO NOT MASTER THE SUBJECTS, JUST PASSED TESTS

THEY NEVER HELD A VOM AFTER COLLEGE.

THEY JUST REPEAT THINGS.....

MY TUBE AMP JOURNEY - EARLY TO PRESENT

The photo below was developed and enlarged by Me.

I was really into B&W film photography and probably Tri-X judging from the Grain of the photo below.

I developed and enlarged the photos at home.

A hobby my Grandfather enjoyed with Me.

My Camera was an Olympus OM-1 Black Body SLR, Zuiko 1.7 Lens

My Enlarger was a Bogen T-35

Boy... I miss that OM-1 w/Zuiko 1.7 Lens

That  Camera was awesome until it was stolen from my house.

I also miss B&W Photography

It gave me a manual ability that Digital does not offer to express myself.

Then I also used to set my Shutter and Aperture manually, as real Photographers develop

a special sense of how best to set the Camera for amazing Negatives

Microdol for Film, Dektol for Paper, then every now and then experimenting with

boosting the film speed with special chemicals called ACCUFINE, tons of fun.

B&W PHOTOS CIRCA SUMMER of 1975

i was into elton john, black sabbath & alice cooper

led zeppelin, aerosmith, pink floyd, the who, YES, BOB WELCH, STEVE MILLER, foreigner

camel, elo and more of those old bands we boomers grew up with

yet ATTITUDES HAVE NOT CHANGED MUCH I CAN SEE......

Then, i went on the HF BANDS

WITH CW - morse code in the 1980'S

DOZENS OF CONTACTS AROUND THE WORLD

"In The Beginning"; Yoda created the LP once Edison proved it worked...

It all began....., in a Neighborhood....., far....., far away

On a lush tropical island, back in 1973 A.D. when I owned and enjoyed my first 1950's Tube Amp

ironically I was not impressed when comparing that old 50's Tube Amp

 to the fabulous Solid State of those times, yet I was lucky to have an Amp at all.

#1 - My very first Tube Amp from the late 50's - Mono in 1973

So here is my very First Tube Amp - was a used "Dictograph" Mono-6V6

my only known B&W photo is shown below the nice color photos.

If I ever find the Negatives, I may have more Pics from that day.

These Color Photos, are from a Reverb posting, great pictures, brings back lots of memories.

This Tube Amp lover, made a nice wood/formica front panel, preserving the original Faceplate/Knobs

Now that is creativity, I recall the threaded shafts were quite long.

The original cabinet was made of plywood and a nice dark oak veneer.

The cover was removable.

My Cousin, deliberately left the amp ON when we went to the Mall

I specifically asked Him if He powered the amp down... He said YES.

I was around 13, He was just 11.

My cousin was a rascal.

When we returned Home, the room was full of Smoke, the fuse did not Blow

and the Power Transformer melted......

He thought it was funny, I was upset.

NOTE THE OLD ELECTROLYTIC CAPACITORS - THESE REALLY GOTTA GO!

BUT IT LOOKS SUPER CLEAN.

THESE RECEPTACLES WERE MOTOROLA TYPE F

I WOULD REPLACE THE METAL CAN CAPS RIGHT AWAY

THE AMP IS IN GREAT SHAPE, OBVIOUSLY NOT IN HUMIDITY

Current status - some unknown Landfill in Puerto Rico

 The Amp was thrown in a dumpster in 1975... a sad day, I was young and careless.

Then I had a Solid State Youth, until I turned 35, when Tubes became my paradigm

I would Play Billion Dollar Babies until my Neighbor complained

I had a 45 rpm of "You won't get fooled again" and we used to scream along with Roger

"Night's in White Satin" 45, with "Cities" on the flip side.

The Monkees, and lots of 60's LP's were played, the Age of Aquarius was finally here.

I was very young, and just starting to open my eyes to the 73' Arab Oil Embargo.

The Americans would ask me; "What is Hay Gas?" alluding to the signs at the Gas Stations.

Hay Gas were the signs posted at Gas Stations, the Non-Spanish readers would ask me

"What is Hay Gas?", I would tell them Hay in Spanish is "we have" or "there is"

So much for Gas made of Hay :) hahaha

Too many Gas stations would run out and the lines of Cars were long

Overnight, Gasoline went from 0.35 Cents per Gallon to 0.78 Cents.

Mom could no longer fill up our 1971 Chevy Nova with a $5 bill with change leftover

We entered the new Petro Dollar OPEC backstab, when we make shady deals with Shady folks.

#2 - Philco Stereo (Grandpa's) - 10 wpch, 1975

Current status - Same unknown landfill in Puerto Rico

The next Stereo was a Philco that came with a separate Turntable and Speakers all of the same brand.

After I threw out my Mono Tube Amp I was amp less for probably 5 month's.

This was Grandpa's Stereo, I asked Him for it as it was sitting on His shelf for at least 5 years, abandoned.

The photo above is the next model in the line, as I don't find a photo of the actual amplifier.

This was typical of those times in the late 60's and early 70's when folks purchased

$200 Stereo's with Speakers, Turntable and Amplifier, speakers that a "breeze" could Blow Over

I wired a Headphone Adapter into the RCA Speaker Outputs and basically used a pair of SONY DR-5 Headphones

on the Amplifier Output, awesome sound, but I could not turn up the volume past 2 O'clock as I would have gone deaf.

This amp saw my Zeppelin, A.Cooper, B.Sabbath, The Who, etc. Rock formative years, as I started to smoke Marlboro's

This amp was at my first Beach House pre-drive's license party, Charlie had a Red Toyota SR-5, and was old enough to drive.

We went out there with Charlie, David, Derek and Howard for some "under-age" Brown Glass Heinekens and some fine Colombian

We played Dark Side of the Moon, about 20x, and a few other Rock Albums, we goofed around and had a blast

 at midnight we went across the street to the Beach, enjoyed the Moon and the Cool Water

We had a blast, as I was initiated into a new realm of zero parental supervision

We were free, appreciative and super responsible

We left the Beach House sparkling clean and took the trash with us.

Unforgettable weekend, and many more Beach House events that unfolded.

#3 - Pioneer SX-450, 15 wpch, Ft. Buchanan PX - 1976

Current status unknown - a thief stole this one from my house

Speakers were my friends Olson's from Texas a popular Japanese US Audio Chain store

 Pioneer was purchased new at the Ft. Buchanan PX in probably late '76

The amp lasted about 5-6 month's, then my Home was broken into, so this Amp and the Pioneer PL12 Turntable were stolen

along with the Kentucky Fried Olson's (victims of a CYGNUS X1 overload)

I toasted the Olson's by pushing CYGNUS X-1 to insane levels.

The Rocket Audio did them in.

If I recall correctly, this Amp had a cost of about $150.00

The PX used to get the Japanese products, way before the local market, they came direct via AFEES from a Far East Warehouse.

Sadly, I did not own or enjoy the Pioneer long enough  but I do recall the following

My friend's father's face when I played "Fly By Night" for Him, on my Sennheisers, His smile was unforgettable.

The other Memory was when Fico came over, with a brand new "Wish you were here", with that dark-blue plastic covering.

I recall the cold Bottle of Blue Nun White, and some Swiss Cheese.

Fico laughed himself out of the room as soon as the Band came in

after that long intro to "Shine On You Crazy Diamond".

I was left alone, with the rest of that album, it literally altered my perception on Music with Sound effects.

He asked me to return it, after I made a Cassette for our 1973 Civic.... played it over and over.

Actually I took the LP to High School, and remember Nick Matos making fun of the cover and inner sleeve art.

My memory is both a Curse and a Blessing.

Technically I am able to recall specs, numbers and details from 50 years ago.

But, I cannot seem to remember people's names unless I call them a few times.

Yet I never forget a face or a piece of equipment that came across my life.

#4 - Technics SU-7300, 41 wpch, Ft. Buchanan PX - 1977

Current status - gifted to my Cousin whose Son Marcus, kept it playing

As I went through a few rounds of my  Lawnmower/House painting money

I paid $175.00 brand new in 1977.

This amp lived with me for many, many years and never gave up!

As a HS student, buying a Technics SU-7300, 41wpch & Bose 501 Series II phase from '77 to '86

That was big news in my small circle of friends, this is my RUSH amplifier 2112 and Xanadu

The Bose 501 speakers, I purchased @ the Sabana Seca PX, because the Ft. Buchanan, did not have Bose.

The story of the Bose 501's, I actually had purchased Technics SBX-50 3 ways 1 month prior.

The Bose, I purchased at the PX for Mom's cousin Angel.

But when Angel heard my Technics SBX-50's, He just fell in love.

Current status unknown - Traded for Bose 501's

So I traded out the Technics BSX-50's, for the Bose 501's.

Bose 501's were gifted to Gary Bonderenko and

I had replaced both 6 Ohm 10" Woofers

Angel was into Sibelius, I was into Deep Purple, 501's offered a more realistic Rock user experience

Today I would have wanted the SBX-50's as my Musical fortitude for High Decibel Music has waned

Then many, many, too many of Vega Baja Parties - if you remember being there, you were definitely not present :)

This Technics SU-7300 amp went from P.R. to FIT, then back to P.R. when I graduated

I mailed it and the Technics Turntable to my Cousin Jorge in Tampa, when I got an Onkyo.

Jorge was awesome as He sent me by Air Freight a ton of my College things like a SHARP Color TV, etc.

He was a trooper, and did me the Huge Favor as I had left my stuff at His house in Melbourne when I graduated FIT.

The SU-7300 was with me during my full 4 years of FIT College, I found a photo below of my Southgate 1985 dorm.

This amp would just Blow Fuses if pushed hard, but always worked.

If my memory is correct this amplifier used a "Current-Mirror" circuit topology.

GRISSOM HALL, THIRD FLOOR DORM 1982

FIT APARTMENT 105B SOUTHGATE 1985-86

BELOW AFTER I GRADUATED COLLEGE AT MOM'S HOUSE IN PR

JUST PRIOR TO MY ONKYO 105 WATTER

HECTOR ALEMAN GAVE ME THE TECHNICS EQUALIZER ON PHOTO ON LEFT

AND THE OLD CASSETTE DECK THIS WAS 1987

THAT DECK RAN SLOW, BUT WAS FREE!

#5 - Onkyo Integrated, 105 wpch, '87 w/Tuner

ordered by phone; Stereo Discounters, MD.

(Stereo Discounters had a healthy Mail Order business in the 80's, BUT closed the year after I ordered my Onkyo)

https://www.mcall.com/news/mc-xpm-1988-03-11-2613214-story.html

Current status unknown, gifted to Len Elias who used it well

Also purchased a pair of Infinity RS-101, 2 way speakers from Plaza Las Americas.

The Stereo Shop that was across from La Esquina Famosa, next to the Gorbea Eye Center

I just cannot remember the name of the Store, but they sold all types of Stylus and Phono Cartridges

Gifted to Chris Fauser in 1992 in Lynchburg, VA

When I worked at Rosy Roads, used my Paycheck, no more Mowing Lawns.

On Base I almost doubled my Pay, by leaving Motorola, but would return to Moto one last time until 1991.

This amp was the highest power I had or have even owned.

I fried my Bose 501's Tweeters with Yes songs, cranked up' to insanity levels.

These Infinity Speakers were the replacements to the Bose 501's.

this Amp eventually got the

Tropical Salt-Air Blues so I gifted it to Lenny before I departed Puerto Rico for the Mainland in 1991

Lenny who got it going, enjoyed it, until again.

We took it out to Vega Baja and I blew out my JBL LS500 tweeters on Alan Parsons "Instrumentals"

so the hearing protection was optional, and recommended.

The JBL LX-500's were from Circuit City, Lynchburg, VA and I had brought them back Home in 1996.

Prior the JBL's I had Cerwin Vega VS-120's that were okay sounding.

But I was never impressed, the JBL's were a far more refined sound.

Circuit City had a no questions asked trade-in policy for Speakers

So I took the Cerwin's in after 4 month's and walked out with the JBL' 3 Ways...

Man those JBL's really sounded musical, and lasted until I replace the Tweeters with an EBay find

and gave them to Lenny who I hope is still enjoying them today after a few Woofer Re-Foams.

Note that Foam and Rubber Woofer surrounds only last 5 year in the tropics if lucky.

Rubber Belts turn into Goo and sometimes become Green with fungus

My Linn LP12 Belts would last about 5 years before succumbing to the Salt Air

This Onkyo was amazing and I loved the Remote Control....

#6 ADCOM GTP-400 and GFA-545, 100 wpch - Audiotronics Roanoke, VA.

Financed with AVCO; close to $1100 USD for both w/ VA Taxes

Current status SOLD on EBay, GTP-400's do not age well

Current status OPERATIONAL. ADCOM made awesome Power Amps

Tuned-up at Audiotronics in 2011-12 and still pushing out 100 Watts/Ch in 2023

Financed at Audiotronics, Roanoke in 1992, I still have the GFA-545 Amp, I sold the Preamp years ago...

These were used initially with the Cerwin Vega's then settled with the JBL's.

The FM section on the GTP's are notoriously bad, mine was no exception, the factory could not fix the FM.

Sensitivity was so bad, FM local stations would barely register on the signal meter.

In 1997 the GTP-400 Source selector switch, developed an intermittent Right Channel

Not even an Authorized ADCOM factory service in New Jersey could fix.

The GFA Amp returned to the US in 2010, and I took it into Audiotronics, in 2017 for a tune-up, still works like a champion

The GFA rocks my Zu Druid speakers as my ROKU-NETFLIX/YouTube basement setup

The GFA is driven by an Onkyo Solid State Preamp from EBay, it is musical as can be for $99.00

So I can suggest a old Solid State Preamp with a Tube Power Amp is a great "Entry Level" combination.

Unless one can get a not-so-noisy Tube Preamp, a Solid State Preamp is a cleaner entry level pathway to Tubes.

I use my Transcendent Sound Phono Stage into the $99 Onkyo Preamp, bypassing the "On-Board" RIAA

What I love about the Onkyo, the Bass Loudness Control is variable, and I can dial-in the heft for Movies and Sound Tracks.

For sound effects, nothing is belter than Solid State; THX, Dolby, etc. all synergize well with Movies.

Also Multi-Channel Home Theater is almost always the exclusive realm of Solid State.

I can unequivocally state that ADCOM GFA amps are a quality product, ADCOM Preamps, mostly so-so.

The ADCOM GTP-400 Preamps are victims of the "large single PC board" syndrome....

My humble opinion is that separate PC Boards would have improved the ADCOM Preamp reliability, but driven up cost

The GFA series Amps are tough as nails, even used it once to amplify a Band at my Beach House...

ADCOM GFA's are great for bright - edgy Speakers, these amps are very smooth and relaxed

Some even describe them as 'dark sounding', I just love them for being smooth and refined, laid-back.

I began in 1992 with the Infinity Speakers, but then I went for the Cerwin Vega VS-120's

Traded back to Circuit City in 1992 for JBL LX500's

These could Rock, but were far from refined, actually they were not a good match with the ADCOM GFA amplifier.

The sound was edgy and bright, maybe they just needed to break-in. After about 3 month's I grew tired of them, and

they would blow their Fuses when I cranked them up with my Thorens TD-280 Turntable so...

I went back to Circuit City and the Salesperson told me that they had a no-questions asked Speaker Trade Policy.

I took these back and left with a Pair of JBL LX-500's, now I had the Music I was missing.

The salesman at Circuit City in Lynchburg VA was actually a Sales Woman

Unusual for Hi-Fi Stores, but very cool indeed, She knew her stuff well.

Traded-in the Cerwin Vegas for the LX-500's

Now these JBL's delivered great music

#6 BOSE 901 Series IV - Lynchburg, VA.

From these speakers I moved back home to Puerto Rico and did two things.

I made my Oak 2 Way AUDAX Bookshelf Speakers and also bought a pair of Lowther 1.3's

These JBL's lived with me for many years until I got a pair of Zu Audio Druid MK4's in 2006.

that are my main speakers to this day. Apart from Pilot PSV-2 and Bose 301's.

My High School Algebra teacher and Soccer Coach gave me a Pair of Bose 901's that I eventually

gave away to my Friend Joe for His Birthday.

I enjoyed the Bose 901's but thought that Joe could make better use of them.

Bose 901's are best for DVD and BluRAY Live Concerts, they just make it seem real in bare walled rooms.

LYNCHBURG VA BOSE 901'S

I have not purchased any new or used Speakers since 2016 and I don't plan to until maybe 2026 when I

plan to lay down Cash, or Finance a pair of $5000-10,000 speakers, the sweet spot between elegance, forgiveness and freedom

to play lots of recordings both Good, Not so Good and just plain raunchy but tolerable.

IF THERE WAS ONE SINGLE INSIGHT TO NOTE ABOUT OLD TUBE EQUIPMENT

WHEN THEY ARE OVER 50+ YEARS OLD, THEY ARE NO LONGER REPAIRS

THESE ARE ACTUALLY RESTORATION PROJECTS

Stromberg Carlson AV-39 Mixing Preamps - In the queue for a restoration

NOTE: This manual was prior to ZIP Codes

Dallas 1, TEXAS..... that's old time

before this stamp 4 sure...

 MY "MOLESTED" MARANTZ EPISODE

EXORCISING "EVIL" UNCLEAN LEAKY POWER SUPPLY FILTER CAPACITORS

My last fix before moving away from my Puerto Rico in 2010

It's been 12 years and counting, since these Marantz

came across my workbench, rare pieces indeed

MacArthur once said it well "I shall return"

The older they are, the better to "Molest" and Upgrade...

The Marantz Tube Preamp and Marantz 9's needed a few oozing/leaky/crusty Electrolytic Capacitors replaced

These arrived at my home virgin, Un-Molested. I popped the bottom covers and found electrolytic capacitor goo on the bottom plates

Rule #1: With old classic amps, NEVER JUST PLUG THEM IN AND TURN THEM ON.

Always perform a visual inspection and don't believe in Santa Claus or Reforming Electrolytic Caps.

When Electrolytic Caps are more than +40 years old.. OUT THEY GO.

And Yes, I am of the school of thought that Amplifier Molesters are innocent of all charges, most of the time.

Just changing parts and components, for the heck of it, to please the 'imaginary' goal of 'sounds so much better'

that is not my game. But I do not doubt that a $110.00 Vcap sounds great, they do, i use them sparingly with awesome results

But the magic, the real art is knowing if the Classic can be improved with just simple things.

I change parts only when necessary, by inspection and measurement, not imagination.

There are a staggering number of YouTube videos that claim to show how to reform old capacitors

The famous Marantz 9 Tube Monoblock Amplifiers

Yes I actually worked on these and enjoyed every last minute

The Marantz 7 Preamp was in better electrical shape.

The Marantz 7 Tube Preamplifier

THE AMOUNT OF MONEY PEOPLE PAY FOR THESE CLASSIC MARANTZ IS BEYOND ME.

I GET THAT THESE ARE RARE, BUT AS FAR AS PERFORMANCE, AT 1/2 THE PRICE ONE CAN DO MUCH BETTER

IF WOULD RATHER BUY A BRAND NEW SOLID STATE PREAMPLIFIER WITH ALL THE BELLS AND WHISTLES

AND LEAVE THE TUBES FOR THE POWER AMP DUTY.

VACUUM TUBES IN PREAMPS ARE GREAT, BUT THE NOSTALGIA SOON FADES WHEN

YOU START TO SPEND MONEY ON LOW NOISE TUBES INSTEAD OF WHERE IT'S REALLY NEEDED.

TUBE PREAMPS ARE INHERENTLY NOISY CREATURES, AND I SOLVED

THIS ISSUE BY BUILDING A FEW AND REALIZING I WAS ALQWAYS FIGHTING THE NOISE.

NOW I USE A $99 DOLLAR EBAY ONKYO PREAMP AND THE NOISE IS GONE.

I AM SAVING UP FOR A BETTER QUALITY SOLID STATE PREAMPLIFIER

AND MY TARGET IS GOING TO BE AN ACCUPHASE SOLID STATE

PREAMPLIFIER, THAT MY FRIENDS IS MY HOLY GRAIL.

My special version DYNACO SA-35 Stereo Amplifier

Sweet, sooo, SOOOOO sweet.

If this one had real Z-565 OPT's OMG!!!

But these newbies OPT from DynakitParts are awesome.

I do miss not having a 16 Ohm tap as I don't own of like

4 Ohm speakers, I avoid them unless I have to own a pair.

My Audio Speakers are all 8 Ohms or higher.

How's that, for an opinionated 62 year old geezer.

6.12.22

Great musicality

The sweet sounds of the classic ST-35 circuitry, very polite Bass

Quite musical, non fatiguing sound, marathon listening capable

Secrets shhhhh: I have a pair of real NOS Acrosound 4-8-16 OPT's lined up for a future SA-35 Build

I may offload the SA-35 below, if you are interested just e-mail me, I am open for trades.

MULLARD 5/20 MONOBLOCK AMPLIFIERS

THESE ARE REALLY WORTH BUILDING

I SHOULD MAKE SOME PC BOARDS.

7.11.22

Sharp, nimble, detailed & precise, good satisfying tight Bass

The EL34 optimized for 6600 Ohm Push-Pull Primary

Design Circa 1959

This is the amp I would recommend for all around listening

8.13.22

My AIKIDO now has V-Caps....

OMG, the detail, the dynamics and the clarity

Just like Legally Blonde - "Bend & Snap"

As soon as I pushed Play on my NjoeTjoeb CD player

the world suddenly became a better place

SR-91 AURORA 6F6 STEREO NFB PUSH PULL AMPLIFIER

Loving the 6F6G Tubes from Ikraine

I ordered a fresh Octet of Russian 6F6S from Kyiv

on EBay, I hope this senseless War ends.

I have been ordering Tubes from this Ukrainian seller for at least 15 years

Top Shelf Tubes, zero BS, well packed and super reliable.

Packages are taking 30 days from Kyiv now so be patient.

YES WE HAVE ANOTHER WAR, NOT THE EAGLE BUT THE BEAR

I write these words as V.Putin keeps throwing influential people out of Windows.

V.Putin is in a very expensive, self-delusional, KGB, Stasi-Nazi-Hunting Safari Special Operation

He needs some Tube Amplifiers, and Music to calm His mind down.

It makes no sense to be in a Demographic Cliff and then send your Young Men to Die.

Wars really screw up the Gene Pool, we lose good Men, often for nothing worthy other than a Dictator's whim

This has been true for as long as Men (and Women) die in Battle.

We never send the Weak and Feeble to War, until now, so the

new Battlefield is de-evolving right in front of our very Eyes.

When older Men defend their Nation, the more able Soldiers can be more effective.

The invader must be very careful to volatile sovereign nations

Unless you wipe it all out and kill them all, Guerilla Warfare will be the invading nation's downfall.

In our Country, we use Prisoners to make License Plates and to Weed the Highways

V.Putin uses Prisoners to do His dirty work, and they could not GAF.

Hey V.Putin, give me a Call, I can suggest a few Tube Amps for your

Tchaikovsky Collection....and your Warmongering obsession.

TELARC 1812 Overture can soothe your anxieties...

Now back to the Aurora...

The Octet of Russian 6F6S have arrived to Rochester

The Parcels from Ukraine are slow moving.... as expected

But the fresh 6F6S have arrived.

I will Tube-Up and place the Aurora in Service

with my Focal 706V's at 8 Ohms

I have my collection of Jazziz CD's all lined up

My Pilot PSV-2's will be on duty at my Cousin's home

They will look great I am sure.

BEFORE THE NEW TUBES, PRIOR DUTIES IN VIRGINIA

6F6 METALS ARE GETTING SCARSE..... THEY WORK WELL.

This is the amp above that inspired me to build my first all Tube Guitar Amplifier...

The NeoClassic30 is 1/2 of this amp with a 12AX7 Preamp in front of the 6J5.

My September Amp Rotation

ROTATION START DATE (September-October, TBD)

AFTER THE NEW RE-TUBE ON 9/10/22 IN ROCHESTER

The 6J5 are Italian FIVRE with the Italian Government Stamp

The Rectifiers are 5Y3 from www.angela.com (the prior had 5V4) SOVTEK badass tubes

The 6F6S Tubes are from Dmytro in Kyiv

The 6SN7's are Chinese SINO, wonderful and musical, they need plenty of break-in to smooth out.

I plan to fire this up soon with the Focal's and also the Focal 706V.

HERE IS THE LATE SEPTEMBER AMP ROTATION FROM 9/23/22

BUT MY CAMERA BATTERY WENT OUT SO I TOOK THE PIC TODAY

Photo - Rochester NY

7AM

The Ukrainian/Russian 6F6S Tubes are on-duty

All Glass, NFB Push Pull Stereo Amplifier

When was the last time you heard a Push Pull Triode Amp with no Feedback?

My FM Tuner is picking up Listener Supported Jazz 90.1 Rochester NY

The station is very near my QTH so I barely need an FM Antenna

The new item in the photo is the D'Addario Power Center

It's the best $50 you can spend for AC Noise Filtering, cheapskate alert!!!!! (myself included)

https://www.daddario.com/products/accessories/power-solutions/power-cables/tour-grade-power-base/

FALL IS HERE!

THE LEAVES ARE STARTING TO CHANGE

9/26/22

UPDATE... SINGLE TUBE FAILURE

ONE OF THE NOS 6F6S TUBES LOST A FILAMENT

IT OPEN CIRCUITED, WENT DARK.

I had 3 spares so I dropped one into the amp and done.

When buying large groups of Tubes, I often expect some fails.

11/12/22

Winter has arrived in Rochester!

The cold weather has me playing Guitar in my Basement, and I am going ELECTRIC.

So far I have not had the motivation to build something, but....

THE CATHODE FOLLOWER AMP IS CALLING MY NAME

ALSO THE CAT-1 PREAMP KIT IS YELLING AT ME.....

During the Holidays, I will make one or both...

Future Amplifier Audio Schedule:

KISMET 1.0, ShermanAudio Dynaco MK3's , Atma-Sphere M60 MK2.3

Owning multiple Amps requires using them all

Leaving an Amp sitting idle for more than 6 month's is not suggested

I also am building the CAT-1 Kit and the Cathode Follower from Bruce Rozenblit

I want to ask Bruce for a Front Panel... I will send Him a message to see if He has one

for Sale...

Q4/23 Office Audio status report

Smooth Operator, Multi-format Music inside of the Wireless Age, the clash of formats!

ONKYO P-301 Preamp, SA-35 Tube Amplifier, TEAC Cassette, OPTONICA FM/AM, Njoe Tjoeb CD

Bluetooth Stereo Receiver, Denon DCM-360 HDCD Changer, Focal 706V, Balanced Power AC Transformer

Current - Q2/24 Office Audio status report

Now this got interesting. I managed to get my Olson AM-240 operational after 20 years. This amp was super problematic, it had a bad Power Switch that finally failed 8 years back. I tried to get it working smoothly but it kicked me back. So the culprit was that when I was recapping this in San Juan in 2003 I left a Left Channel Phase Splitter wire disconnected! It was always distorting on the Left Channel.

So now after a few hours on the Bench, I have it working with all good Tubes, especially the 7189 Russian version 6p23pEB that are amazing at 430 Volts on the plates. This amp puts out 23 watts solid just before clipping.

The sound is quite nice, and I am glad that in the past, some owner did not use this amp with normal regular 6BQ5/EL84 Tubes. Despite popular Lore, the EL-84 will not work in Amps that need real 7189. But on the contrary 7189 will work perfectly in EL84 amps.

If a 7189 amp operates the plates under 400 VDC then a 6BQ5/EL84 might be a suitable sub. But why risk the Output Transformer primaries. When a 6BQ5/EL-84 tube decides to run-away, it can often melt the Output Transformer primary bobbin wire, causing a catastrophic failure of the Primary, and an expensive re-wind if you can find a place that does a good rewind.

If you use EL-84 Tubes in an amp that has more than 400 Volts on the Plates, I wish you a long life, as neither the Output Transformers, and Power Tubes will last long. And if the Primaries of the OPT don't burn, You got lucky. I had an AM-240 that was roasted that I traded for the Top and Bottom Covers. I traded for my old Harman Kardon A-300 and 8x 12AT7 Telefunken Tubes.

Good trades, meh. But I am glad this AM-240 is kicking A again. I replaced the loose Volume and Balance knobs with Black/Silver Radio Shackers and now I canm actually see their adjustment from my Chair. The original skinny knobs are had to see where they are in their rotation.

One thing, this amp uses the hard on RCA cable input jacks like old Pioneer and Sansui. So you are best using normal RCA Cables, the good stuff does not fit and usually hums The Phono Stage is great as well, it had an open 100K Voltage Droppinf resistor that I finally found, as the Phono stage was broken since I bought this on EBay back in the early 2000's.

I also have my old ADCOM ACE-1 AC Enhancer that saved my System in a 1999 Y2K Party.

New AC Power Switch installed, I had to snip off some metal so that the switch could just push into the existing rectangular

front panel opening. The AM-240 is amazing, the factory Output Transformers have terrific Bass.

Now all I am waiting for is the replacement ALPS Stereo Volume 500K w/Loudness Tap

plus the 0.047uF/600V MPW Illinios Capacitor Poly Caps to replace the Brownie 0.047uF NTE's

that are not known for being the ultimate in musical prowess. My strategy with restoring

old amps like the one below, is not knowing in advance whether it will ever be a reliable daily player,

I prefer to use standard economy 600V Signal Caps until I know for a fact

that the Amp will play. In this case I ordered the (4) Replacements and changing

them will take me no more than 30-45 Minutes depending on the Oscilloscope

test for inner and outer foil orientation, that I always try to respect with signal caps.

The Headphone Jack is next and I also plan to re-wire the Tape Head input to a normal

Tape Mon input as nobody today uses Tape Decks that just has the Head connected to the RCA

jacks with no internal Tape Head stage to correct the curve, similar to RIAA but for Tape Heads.

The Tape Head input is one that went obsolete many decades back, and in this AM-240

is just a Wasted Input. I will have to bypass the Tape Head equalization and connect the RCA

directly to the rear of the Phono-Tape HD switch, easy enough for Me.

MULLARD

In the book below, you cannot purchase any of these designs, they all just plans to be made by hand.

This book is full of wonderful schematics just waiting to be discovered and assembled.

There are som many secrets in this Book, about Push Pull amplifiers that most

readers will gloss over them.

The few who have actually built Mullard Amps, have likely faced adversity, then pure sonic bliss

The Mullard sound is unlike any "Push-Pull EL34".

These are authoritative, direct, and have rock solid stable performance with lots of musicality

It is evident from the Mullard Book, that the designs, were optimized around the EL34, EL-84, ECC-83 and EF-86.

These amps have excellent amplification measurements, and require very little drive
In fact I would advise NOT to use a 1 Meg Volume Control, go to 500K or even 250K.

I dropped the 1 Meg Input Potentiometer to 500K, and it dropped the noise floor, 500K it is.

My Mullard 5-20 were built on discarded Leslie 147/122 "Rescue" Steel Chassis

they dulled by Hole Punches, and were difficult to work with.

Thick gauge Steel is not friendly, and in 1996 this was my first Tube Amp build.

These are in fact my very first hand made Tube Amps and took years to perfect.

I learned so many things by iterating on these, they were a School in Tubes

My layout screams Cary Audio as I used to enjoy their brochures in the 90's

also by reading lots of Stereophile when the magazines were the size of a Readers Digest

Then I so loved the NeoClassic30 knobs, so I put them on the 5-20's, they match the Brass plates.

I have enjoyed these amps more than any other, and have upgraded them

dozens of times. I have fried Tubes, Resistors and Popped Capacitors.

Yet, now these are my true first DIY loves, an almost 30 year relationship.

 

Cathode Bias, 20 Watts, Pure & Dynamic, fast and open

Ultra-Linear, Push-Pull 6.6K Primary

Designed by Engineers at MULLARD LTD. in 1959

A WORTHY DIY PROJECT TO CONSIDER, PHENOMENALLY MUSICAL

EXQUISITELY CLEAR PRESENTATION, IF YOU WANT TO GO 'ALL THE WAY'

THEN CONSIDER SOWTER TRANSFORMERS

THESE AMPS HAVE GRACE, BUT ARE NOT POLITE, THEY ARE "IN-YOUR-FACE"

NOTE THAT KT-77's WILL PUSH THE SOUNDSTAGE BACK A BIT WITH SMOOTHER SOUND

IF I GET ENOUGH INTEREST, I WOULD PROBABLY HAVE THE MULLARD CHASSIS BUILT AND

MACHINED WHILE ALSO USING SOWTER OUTPUT TRANSFORMERS.

THIS WOULD BE MY FIRST COMMERCIALLY AVAILABLE AMPLIFIER.

MY TAKE ON

CLASSIC TUBE AMP HYPERTENSION 

"Un-Regulated" DC Power Supplies on most Classic

Tube Amps built in 1950's and 60's and earlier

These Power Supplies do not work as well today

When you home voltage climbs past 120VAC

Now for the practical explanation that anyone can relate to...

HOW CAN YOU TELL

 THAT YOUR TUBE AMP IS SUFFERING

FROM POWER SUPPLY HYPERTENSION?

VERY LITTLE, OR NO DEEP BASS

 EDGY SHOUTY MIDRANGE

 STRAINED UPPER FREQUENCIES

LISTENER FATIGUE

AUDIBLE BUZZING AT YOUR CHAIR

POWER TUBE FILAMENTS LIGHT UP A DARK ROOM

 THE PLATE/FILAMENT TRANSFORMER OPERATES VERY, VERY HOT

YOU CAN FEEL THE TRANSFORMER VIBRATE

YOU CANNOT HOLD YOUR HAND ON THE POWER TRANSFORMER

Now read on....... and enjoy valuable Tube Saving insights

Not a keyboard jockey, but a real Engineer.

Electrical Engineering Degree 1986

 Professional Engineering license, PE. 2004

FCC General Radiotelephone with Ship Radar Endorsement

 Member of IEEE since 1982

Amateur Radio Extra Class since 1988

I am not an influencer

I actually make things happen

110 VAC, 115 VAC, 117 VAC, 120 VAC, 125 VAC

What is the insight here?

Residential AC Power has changed, as the years have passed us by

We live today in a Solid State Modern Electronics Age.

 Power Supplies are now Primary Voltage agnostic

they all (and I mean 95%) have some form of DC Voltage Regulation.

By implementing DC Voltage Regulation the DC Power Supply is primary agnostic.

Power supplies today are pretty much agnostic, to the Primary AC Mains at your Home receptacles.

When that piece of equipment, is connected to 120 VAC

 the DC supply regulator produces a steady 15 VDC.

When connected to 115 VAC the Power Supply still produces a steady 15 VDC

When connected to 117 VAC, you still get 15 VDC.

And when the Mains rises to 125 VAC, you still get 15 VDC.

If the primary voltage goes above 130VAC, the MOV will fire and the fuse will blow

This is called :DC Voltage Regulation:

But thus is also absent in 97% absent from Classic Tube Preamps and Tube Power Amp Power Supplies.

Some Classic Amps like a Grommes 260, used a Gas Regulator Tube to regulate the Screen Supply.

So when the AC Voltage feeding the Primary of your Tube Amp increases past the design specification

of the Primary Voltage tested at Full Load on the Secondaries, the AC and DC voltages rise and fall.

Hence there is no :Regulation:

If the AC Mains voltage rises to 125 VAC; a regulator would control this, and produce 15 VDC

as in my previous example.

But regulators have a lower limit and when the AC voltage drops down below this lower limit

the regulator stops wlorking, and the electronic device it is powering will stop working.

When a Voltage Regulator circuit is not getting enough Voltage to be able to regulate it.

or if the Regulator gets too much DC Voltage, it can burn out, there are upper and lower limits.

Have you ever had a brown-out at home when the AC Mains drops?

Your Solid State Electronics will stop working while your Incandescent Lamps dim.

This is exactly the analogue to your Tube Amp, the amps in effect Dim out until the Music sounds crappy.

Just as well, if there is a excess current draw, same, the Regulator can fail when the AC Voltage rises past 130 VAC

of the Metal Oxide Varistor will fiire and short, protecting the equipment from burn out.

The MOV commits electrical Hara-Kiri all in the name of blowing the Fuse.

With Classic Tube Amps, this does not happen, but if you drop the AC Mains let's say below

110 VAC, you will starve the Tubes and it will sound "wonky", until you drop down to 90VAC or less

it will start to sound raspy and distorted.

If the Classic Amp is connected to 130 VAC, it will slowly burn out and this is a fire hazard as the

mains Fuse may not work in time. This is the part where some people refuse to swap out their 60 year

old Power Supply Capacitors, melting the Power Transformer Secondary while the Fuse does not blow.

Tragic ending to a system of beliefs in keeping old amps 100% stock.

Every belief system carries a price to pay.

UN-REGULATED DC POWER SUPPLIES

With newer Tube amps from the mid to late 1970's, no worries.

Boosted DC is generally not a factor on late 1970's Tube Amps, but there are exceptions.

Some 1970's amps may operate their best on 117 VAC, with 120VAC the upper limit

Tube Amps made prior to 1969..... well they don't typically operate well at 123-125 VAC.

A Tube Amp fact: Tube Amps are designed to operate with their Un-Regulated AC and DC Voltages.

When the Mains goes up, so do the DC Voltages.

When the mains drops, the DC Voltages drop as well.

But the Tube Amp keeps working until the AC voltage drops below a lower limit, and the amp sounds fuzzy.

or the AC Voltage rises above an upper limit, creating electrical stress on the Tubes and Components.

Boosted DC and Filaments is all a case by case thing.

So when in doubt, measure your AC/DC Voltages, you might be

surprised or not, depends on the values that you measure.

Note that DC Voltages 10% different from nominal are usually OK

Filaments, they should always be connected to AC/DC voltages within 5% of published spec.

Finally manufacturers have always cut corners for profit

so Mains Transformers could be victims of the "less capacity" for

less price, meaning a Hotter operating Mains Transformer with little

or no headroom for current delivery capacity.

FILAMENTS EXAMPLE:

I have a good proven Tube amp schematic that I want to build from scratch.

"Never use schematics that were never actually built and tested, I learned the hard way"

Stereo Tube amp uses four EL34, two 6SN7 and two 12AU7, with a 5V Tube Rectifier

The 6.3V filament currenty draw will be calculated as:

[(1.5A) x 4] + [(0.6A) x 2] + [(0.3A) x 2] = Total Filament Current Load

(6A) + (1.2A) + (0.6A) = 7.8A

So the correct sizing for this filament load is 8 amps as it is unlikely

to find a 6.3VAC, 7.8Ampere Transformer.

The usual "more is better" does not work here, as the filament voltages are almost always "Un-Regulated"

So you need to have a Filament Voltage that is +/- 5% of 6.3V.

If you use a much larger Transformer capacity, the AC Filament Voltage will not settle

at 6.3 VAC, that is not how Transformers work.

Transformer Specifications have a N.L. (No Load) & F.L. (Full Load)

What you want is to look at: the Full Load Current and size your Transformer for exactly that.

Headroom on Filaments is not cool, Headroom is beneficial for the High Voltage

Winding of the Power Transformer. Here one really wants to use a Transformer

with enough capacity to operate at 70% to 80% of Max HV Load.

Straining a Power Transformer does not usually make a good sounding amp... usually get buzzing and hum.

RECTIFIER TUBE:

This is easy: 5AR4/GZ34 so that one will use a 5V/2A Filament Winding.

Here the good design practice is the same as 6.3VAC, design the load to match

the winding capacity. So the answer here is simple.

Tube Rectifier Tube Filaments are best connected to the exact same Transformer

Current Capacity so if you have two 5AR4 in Parallel, that would be 5V,4Amps.

You really can use a 5 Volt, 5Amp transformer, but that is about the limit.

When you over dimension a Filament Transformer section, you will have boosted Filament voltages

and these can be damaging to Tubes, not the Transformer.

I read a book published in the late 1930;s that provided empirical data in shortened tube life

when Filaments are fed by a voltage more than 10% above spec.

On the other hand "under-dimensioning" can lead to long term Transformer damage.

The rule is to always design your Filaments to match the Transformer winding

for 6.3V, 12.6V and 5V which are 95% of the voltages we deal with on Filaments.

HIGH VOLTAGE:

The High Voltage section, you can add some Headroom here and compensate

with Choke DCR and the correct Voltage Dropping Resistors.

In fact the amps that I build always start with the Power Supply Design.

If our Stereo Tube Amp needs 350 Volts DC at 230 milliamps we need to

look for a Power Transformer with 375-0-375VAC at 250 milliamps.

It is much easier to drop a few tens of volts by using a 375V Center Tapped Section

with 20 milliamps headroom, maybe even 30 milliamps.

It is never wise to use a HV Section that is exactly the full load value

as this will eventually burn out the HV Transformer Section.

The best way I know on how to introduce the correct value Choke and Voltage Dropping Resistors

is to experiment with power resistors and empirically load the Transformer so that

when connected to 120 VAC the Amplifier Voltages measured are within 5% of nominal.

WHY?

All of the Amplifiers that I have built, all of them do noty require a VARIAC, these amp

can all be plugged into 120-125VAC and work very well.

So the goal here is to build Tube Amps that do not require any Voltage Control

and can universally connect to any mains voltage between 117-123 VAC.

CONCLUSION and PREFACE....

Just because the rear panel of your 1959 Tube Amp claims that it can connect

to 125 VAC, believe me, this is usually not the case.

SO WHEN WE THINK ABOUT POWER?

Also when you look at the back of an old Tube Amplifier and read 117 VAC, 200 Watts.

This does not mean 200 Watts of Audio Power!

This means that 200 Watts of AC Power are consumed when operating the amplifier.

P = V * I

200W = 120V * I

I = 200W/120V = 1.67 amps

So the Fuse to protect this amp will be a 2 Amp Fuse.

I really have never seen Audio Output Power indicated on the amplifier itself

but there are exceptions to the rule.

Audio Output Power specifications are usually in the Manuals or Datasheets.

Just enjoy the Music.

This page is a mix of my past, where I spent years of Bench Time at work, then learned by making many mistakes.

Here you can benefit from my real Classic Tube Amp experiences.

This page is about my Tube Amp journey and how I came to realize that some Classic Tube Amps from the 50's, 60's and early 70's

might have a hidden disease the slow & silent "Power Tube Red Hot-Rod Zone"

I went on many "Deep Dives" on Vintage amps (for newer Tube amps, just skip this page)

and noticed a pattern with many of the older amps from the early to mid 60's when

you plug them into 123 VAC, they can run quite hotter than necessary.

It does not always happen, but one always has to look for the signs of Amp stress and recognize it.

When I gathered my test sheets/restoration notes where I wrote down the various voltages across the amps

on their respective schematics, I saw that for each one, there was a repeating theme.

my DC Voltmeter was whispering at me, but I was not paying the proper attention.

Neither was I looking at the Power Tubes, in a very dark room when they were operating

when I was new to the Tube Hobby, who knew, I was into Tubes and had no real experience?

After 2 years, 1996-1997 I realized what was happening, as I saw Power Tube Plates Red quite quickly indeed

when I put the light out at night. The dark ember glow of Red Plates.... OMG!

A few Doctors describe their discovered diseases, by their own names.

But I was not going to call this anything with my name, just call it what it is,

Quads of expensive EL34 matched tubes, kept piling-up on me, way too soon

And the Power Tubes would actually make noises as they warmed-up and cooled down

Like small tingling sounds, such as softly tapping on a Wine Glass with a metal object.

One Caveat;

if your Home Mains is always 120V or less, say 117-119 disregard this topic altogether

You should always check ANY Power Tubes in a dark room to look for Red Plates.

This applies for Homes that have AC voltages greater than 120VAC most or all of the time.

There is a reason why some Homes will consistently have 123-125 VAC from the Outlets.

The reasons why are the subject of a more interesting but separate subject.

LAYMANS EXPLANATION

Power Company Sending End & Receiving End Voltages

In electricity, Power is Generated and also Power is Lost.

Like the efficiency of a Car Motor, only a % of the Heat/Power/Torque Generated

goes to the Drivetrain. Same for Electrical Power Distribution.

The higher the sending end Voltage, the less power is lost across the transmission lines.

Simple Plost = I2 x R

As you increase the Voltage, the losses across the transmission line decrease as the

square of the Current. The Line resistances are steady, so by lowering the current you lose less power to heat.

But lowering the current means boosting the voltage to keep the Power constant.

 Hence, Tube Amps that use un-regulated power supplies can be, (and I caveat this) affected by the Voltage Boost.

Especially Power Transformers with Primary Voltages in the 115VAC Range, wound to meet a standard

that was once okay, but take that amplifier from the late 50's or mid 60's, plug that into

125VAC and you will measure BOOSTED voltages on the DC and also the AC Filaments.

Hence like High Blood Pressure, it is the silent killer....

Note: The only sounds Power and Rectifier Tubes should produce, are out of your Speakers!

If the tubes make noises when warming-up or cooling down, you probably have an issue with the Amplifier.

Vintage Classic Tube Amplifier

"Hypertension Syndrome"

This is the silent Tube Killer, but why Sherman, why do you say this and most Audio Forums disagree?

Why do people come at you with hate and derision when you try to explain Science?

A Wise Man once stated "Ignorance is daring"....

Answer: my Pro-Bono Webpages are my refuge. I am a Science refugee and avoid the world of beliefs and hobby dogma.

I treat all subjects with tons of detail, and mathematical fact. Even at my job I am responsible for minute technical details that can have a catastrophic result if glossed-over.

But again, as I think this is very important to the Vintage Tube Amp Equipment enthusiast (especially on old Tube Power Amps), I will go into electrical jargon, a language that is like learning a new roadmap.

While most of the folks on Audio Forums have great interest, but no idea or 'feel' for what is happening inside their old amps, I hope this will help them understand why their power tubes seem not to last more than a few month's.

So what I am to explain here, relates to all of the precious ST-70's, ST-35's, Mk4's and Mk3 Dynaco's, Scott's, Fisher's, EICOS's, Marantz's, Pioneer's, Sansui's, Kenwood's, Grundig's, McIntosh, Luxman's. etc. Any old 1950's to 1970's Tube Amp may have Hypertension.

When Paleo-Tube units are suddenly transported from 1960 to >> 2021, and operated in "their an all original condition", they are being plugged into an electrical socket that is often (not always) much too high in AC mains voltage.

The old days of no Internet and no Cell Phones, Carbon Paper,Typewriters, Ditto Machines

Those days are long gone.... (RIP), but back is the Inflation of the early 70's, :( bahhhh.

Our power grid today often measures greater than 120 VAC RMS, and this can lead to slowly frying out old Tube Amps, and also over heating power transformers and sending filaments into over-voltage.

If you are one of the lucky who have 115-120V at your home, you can stop reading this, your old Tube Amps will dom just fine.

This syndrome is focused on homes whose electrical mains in the US, territories and possessions never drop below 120VAC and often measure 123-125 VAC, here is where old Tube amps start to sweat.

I think my worst ever case of hypertension was the pair of Stromberg Carlson AR-411, at 121 VAC those amps would immediately boost their DC to almost 430 DC volts and they were not intended for more than 370 volts DC. The Power Transformer primary was wound for 115VAC and the transformer current delivery capacity was close to Imax.

The confusion that sets in when a bottom cover is pulled off and one is just staring at all those parts, who can blame people for not understanding.

Hey even Eddie VanHalen (RIP), knew about Tube amps and Variacs.... Eddie got that Brown-Sound using a VARIAC to lower the AC Voltage on his Tube Amps.

I think that there is no single Hobby that has so many interesting people, yet many totally confused by Electrical Theory and imagining things that do not exist.

People still say, write and believe that there exists 110VAC, this is ancient history folks.

The last time 110VAC was coming out of a US outlet was probably 1950 or earlier.

Not even the Motorcycle and Auto restoration folks, get into so many bizarre and unique conversations on Forums,

A Brake Pad is just that a Brake Pad, a Sway bar is just that a Sway Bar, and those that claim magic are immediately called out on the BS.

But, in the Electrical realm, people come up with some really creative thoughts, not so much Science, but lots of weird misconceptions and ensuing arguments.

You never read about someone saying that Rice Paper Tubing for Brake Lines makes Braking better, you can actually feel the brake pedal more?

And when things really get strange, Room Treatments and all of the things to make a music room sound better with your equipment.

One Shaman was selling Battery Powered Clocks to improve the Sound in a music room (Machina Dynamica fraudsters on Audiogon).

This is just too bizarre for me. Room treatments are absolutely essential, when done right.

Yet this stay-at-home hobby is good for keeping feral Men from Bars and the stray things Wives just hate, maybe that Pot Smoking friend, who always shows up Stoned :)

But you do have people claiming so much stuff on Audio Forums, that is borders on the George Carlin insanity evel.

Insanity mixed with a touch of righteousness, just the right medicine for a soldering session on a kilo buck amp, just to upgrade a few special parts that make absolutely NO SONIC DIFFERENCE and have degraded the value of the Amplifier and make absolutely ZERO sonic improvement.

Replacing old functional Screw Terminal Speaker interfaces for plastic 5-way binding posts, with zero sonic improvement or difference, but the Amplifier just lost value.

I am for Amp Molestation, but not doing stuff that makes no sense. Also people insist on replacing perfectly good RCA Female Jacks (Receptacles), so unless the RCA Receptacle is damaged, rusty or fails to make contact with the RCA Plug Center Pin, leave it alone. Drilling larger holes on Classic Amps for new interfaces is like drilling you 1965 Corvette to accept a fancy new Side View Mirror.

If it is not broken, please leave it alone. The difference between a $1.00 Capacitor and a $100 Capacitor often requires a $5000 amplifier to be able to hear a difference, enough to warrant a change.

I come from the School of, "If it is not broken, don't fix it"

This Sherman learned the hard way, years of Electrical Engineering examinations, literally thousands of hand Calculations and I graduated before students even had Laptops.

Then years on a Workbench at Motorola and GE, soldering, Oscilloscopes, Signal Generators, RF Millivoltmeters, Simpson's, Flukes, Microntas, Network Analyzers, ANRITSU Site Masters....

I used the very first 5-1/4" floppies at Motorola just as I walked out into a Kraftwerk-like World, full of computers and big hair, the 80's was full out. The Music scene was an explosion of modern synth and electronica both European but Global. This seems to coincide with the term World Music.

The Summer of 1986 and the eighties with MTV were on our SHARP Transistor Color TV. People in the 70's even built Color TV's from Heathkits, I found that quite extreme even in the 70's and 80's. even back then I thought that people who wanted to build their own Color TV's were nuts....

So yes, I did code my TI-58C to pass my Chemistry examinations, I put all of the Alkaline and Acid formulas for Ph, kPa, etc. on my TI, worked well that TI, but the HP-41 was a much better Calculator with RPN notation.

So what I am sharing here, I hope does help other Old really the older generation of Tube Amps from the late 50's to early to  mid 60's. Usually Tube Amps made in the 80's onwards are just fine. I am referring to older style Fishers, Scotts, Dynacos.... Knight, Olson, McIntosh, etc.

Tube Amps matter, and there are 33+ years of reasons why I think what we do to improve old tube amps is important for the love of using classic electronics in this New Age.

Not just only for safety, but for the sake of Hiogh Fidelity, and here is my story on this silent killer; Vintage Tube Amp Hypertension.

A PRIMER ON RESIDENTIAL POWER & HOW IT RELATES TO VINTAGE TUBE EQUIPMENT

Maybe on a Hot Summer Day, when the Power Grid is totally loaded with thousands HVAC's units cranking out Cold in your neighborhood homes, our AC Power may just dip way down to 115 VAC RMS, maybe less at 117 VAC MAX in an extreme heat case of 100F degree days. That is a great stable power grid.

But I lived on an Island that had a electrical distribution that was old when I was young, now it is older... much older. Fragile is the word, the Grid is so old and over stressed, the investment required to modernize it are quite high. Without revenues, and so on. So its a tough place with 124 VAC on colder days and 122 on warmer days. Sometimes up to 125.6VAC RMS.

So here is that concept needs to be explained on how Voltage rises and falls when a Circuit loads and unloads like a Transformer, on the "Un-Regulated Power Supply", and this fact is the underlying corrective action needed to ease Tube Amp Hypertension Syndrome. Old Tube Power Supplies don't have regulation. So without it, the DC Voltage of the secondary side of the Transformer will rise, accordingly. The problem comes when the Power Transformer is not dimensioned with any "headroom" in the Power Delivery Department. So this means that when the primary goes from the 120 VAC or even 115VAC that seems to still be a standard in the primary windings along with 125VAC, my favorite tap!

Some transformer designs are inherently "passive" regulatiors with little headroom. Once a secondary winding current capacity is at nominal, any other winding that settles at an above nominal current draw. This is the effect of not having sufficient loading on a Power Transformer Secondary. The trick is to wind the Power Transformer with 20% extra capacity and with a dual primary 117 VAC and 125 VAC, but currently what is used is 115/125VAC vs. 117/125VAC designs, with dual taps on the primary to switch voltages. This is the best way to permanently treat the patient. But this is not always practical to substitute the original transformers. Therefore the only and best solution is to set the Primary Voltage with some type of Box.

Well you can make one easily if you are handy with electrical Boxes. You just get a AC Toroid that has at least 800VA of Capacity and has a secondary that the voltage is set to 55-0-55 VAC. This shaves just enough from the highish primary voltages and steps the voltage down, by just a smidge like 5 Volts... and this is perfect, and the Toroid will provide filtering and isolation from the AC Mains.

Some traditional non-toroid are Ferroresonant by design, so Transformers all have a max and min loading specification, based on a primary voltage (look at the Hammond Datasheet for FL = Full Load, NL = No Load) you get to know what the Full load voltage is. If your filaments require 6.3VAC RMS @ 3A, then put a 6.3VAC RMS @ 3A transformer winding (or section), or a discrete stand alone transformer to do the job perfectly, and with better isolation. Individual Filament Transformers also allow for better isolation to the High Voltages.

Most people think that a Transformer magically keeps and maintains the secondary voltage independent of secondary loading, FALSE. A Transformer has a loading curve and from this you know what the AC voltage is if you know the current draw. The more current that that transformer section pulls, or loads, the AC voltage across those windings will start to fall from a NO LOAD to a FULL LOAD. It can look like a horizontal line on an X-Y graph. This is how you control voltages, by not under or over loading the transformer. It is always best to load each section near or at their designed maximum. There is no fear here as when you properly load a power transformer secondary, the AC voltage developed drops down, meaning that the DC Rectified Voltage is higher than normal. If this boost is more than 5% some amps start to run HOT. While other amps seem fine with a 20% boost over the primary AC Transformer Winding. The closer it is wound to 120V the better, all the way down to 125VAC for Cathode Biased Amps that always can use an adkustment when they are played on a mains higher or lower than at your home. I like having a switch to flip between 115/125VAC.

When a circuit loads a transformer secondary, the secondary current rises rise and the secondary voltage drops a bit, that is called regulation, and the range is how it tries to regulate, but is actually a sloped load line. This is different with Regulated Power supplies that have "Active Regulation Elements" after the Rectifier does the job of converting 60/50 Hz AC to pulsating 120/100 Hz DC. The DC Voltage on a regulated supply is ROCK SOLID until the regulator capacity is exploded and the regulator shorts out. Regulators come in 6.3V, 12V, 24V, 48V, 100V, 200V, etc.

The regulated power supply uses external components (regulators) to maintain a steady DC voltage, but this is a different design than used in Vintage Tube Amps, except the Grommes that used a regulated Pentode mode Screen Voltage. It used a Tube Regulator I think with a 6L6 or a Gas Regulator, I can't recall.

What I am describing here, is not an intuitive fact, but so many people are unaware that their 1975 Dynaco ST-70 is suffering from 123-125 Volts on the Primary.

AC Transformers have two important specs out of many;

Full Load and No Load AC voltages.

Old (and still some New) Plate and Filament transformers were designed and wound for an AC primary mains voltage standard of 115VAC or 117VAC.

So when you have one of these, you need to compensate on the secondary of the transformer, to control the rectified DC voltage to the target value. Just as well the ASC Filament voltages can be higher than 10% over nominal, and tubes can wear our at a faster rate when they are powered with jacked-up filament voltage

People, the 120VAC Primary Standard (if there was ever one) wasn't any part of any manufacturer until maybe the mid to late 90's.

And people today still say "110VAC" and "220 VAC".... this is so passť.

Folks, the last time AC voltage measured 110VAC was probably when Frank Sinatra was alive and well in his early career and homes lacked Safety Grounds or Polarization HOT and RETURN orientation on their AC outlets and plugs.

So when you just plug a Vintage Tube Amp Power Transformer Primary to 120VAC - 125 VAC RMS, the secondary voltages are almost always, immediately higher, and sometimes dramatically higher.

The old Power Transformer will heat up, and stress out, and the tubes, to the point where the equipment can run super hot and the plates on the power tubes start to glow red. Sometimes you can feel a slight physical vibration from the stress on the Power Transformer. The filaments can look more like light bulbs than the deep orange glow.

Now there are exceptions, but believe me, 8/10 old amps that have been on my workbench break out into a hard sweat when connected to 120 VAC.

And being the "tube-whisperer" I am, I can see and feel the pain, just by visual and audible inspection.

I can tell when an old amp is struggling, and can hear it in the way it plays music. I will measure the DC voltage on the first power supply capacitor and like a Doctor taking your Blood Pressure, I can tell if there is trouble ahead.

Stressed-out Tube Amps and Preamps lack "air", they can sound mechanical, lifeless, dry and often stiff.

There can also be 120Hz ripple Buzzzzz on the speakers a few decibels higher than you would like as the Power Transformer is delivering more voltage than needed.

I know descriptions of sound are weird, but this is the best I can to convey audio into words.

Basic Transformer Formula #1

'subscripts' [p = primary], [s = secondary]

Vp/Vs = Is/Ip

Vp= Primary Voltage

Vs = Secondary Voltage

Is = Secondary Current

Ip = Primary Current

Here we have the most basic of Transformer formulas, it describes an "inverse" relationship between Voltage and Current.

The primary and the secondary AC voltages through a Power Transformer always have an inverse relationship between their Voltages and Currents.

And in case you did not realize, and many folks do not, Transformers do not work with DC, Transformers work only with AC.

Why, just pick up a book, Google it and start to read. Read about Nikola Tesla, Westinghouse...

When a reporter asked Elon Musk on how He learned about Rocket Science; Elon responded "I read alot of books"

The only slight twist in the application of magnetic inductance and reluctance are power supply DC smoothing Inductors (a.k.a. Chokes).

Inductors pass DC current while "choking" or smoothing out rectifier AC 120Hz ripple. This is the Law of Superposition, one of the most basic concepts in understanding circuits, look it up, it explains lots of things.

So in simple layman's terms, the way that a Transformer operates, it converts smaller voltages into higher voltages, and vice-versa, and the same for currents.

That is why they are called Transformers, they TRANSFORM VOLTAGES AND CURRENTS.

Another very important learning item is to beat the heck out of Voltage and Current theory and really understand each one to the point where you can take a White Board and explain them.

So with Transformers, we have a combination of voltages and currents flowing in the Primary and the Secondary.

The convention is that the Primary is the side that connects to the AC socket, and the Secondary is the side that connects to your Power Supply Rectifier, and Tube Filaments.

This formula, when applied, produces the results that explain how Vintage Tube Amp Hypertension comes into being.

Just do some basic math, enter three out of the four variables and solve for the missing one. Then after writing these values down, increase the primary Voltage from 120VAC to 123.5 VAC and calculate the AC voltage on the High Voltage Winding and also the Filament Windings, bingo, you just have the first concept of how a Transformer "transforms" Voltage and Current.

Now with a Vp of 120VAC, as in a modern Tube Amp Transformer, Secondary HV Voltages are typically higher, per design and the Filaments are orders of magnitude lower.

Just as a practical example "Solid State" Amps go the other way, these amps use Secondary Vs. Voltages in the 20 to 60 Volt range, even as high as 100Volts. Transistors rarely need very high DC voltages across their P-N-P, N-P-N, or N/P doped Source to Drain Silicon of FETS and MOSFETS.

So when we increase primary AC voltage into an un-regulated and rectified AC to DC Power Supply, this creates a permanent "BOOST" and is always measurable on the Secondary, and often, this is not good news for the Amp and the Tubes.

The solution to this problem is simple, but almost none of the classic manufacturers did this simple fix, just wind the Power Transformer primary for the "worst-case" primary voltage of 125 VAC.

This way the equipment can be plugged into any duplex outlet and be happy.

This is how I DESIGN all of my equipment and power supplies. I baseline the operation on the worst case scenario.

Then I compensate when I have a Plate and Filament Transformer that has a 115/117 VAC primary, so that the rest of the circuits can work when slammed with 125 VAC. It can be done, it just takes some extra math and empirical testing to "park" the Un-Regulated Power Supply in the "neutral zone", Spock states: This is logical.

The exception here, is when the Output of the Rectifier is connected to a filtered input of a Regulator Circuit. The AC wall voltage can go up and down quite a bit, while the Regulator Circuit keeps the DC output rock-steady.

BUT  98% of old Tube Amps do not have DC Regulation. In rare cases as in the Grommes and Leslies, the Pentode Screen voltage is regulated through a Gas Regulator Tube, this lowers distortion, and is a cool thing.

Look it up, I think the amp is a Grommes 260 and the Leslies are the 122/147 Models, they use Tube Gas regulators.

Now about wire gauge.

The "gauge" or the wire thickness of Plate and Filament Transformers for Tube Amps, is usually made of Primary wires that are "thinner" and Secondary Filament wires that are "thicker", generally speaking. The High Voltage section is typically thin wire.

Practical example: How do you think Power Companies send massive amounts of MVA Power through those Short, Medium or Long Power Transmission Lines that cross our lands.

The power company generates AC voltage at approx. 12.5 Kilovolts (Nuclear, Coal, Oil, Hydro, etc.) by spinning turbine generators.

Then they rely on huge massive Power Transformers to "Boost" the Sending End Voltage to basically "Lower the Current" across the Transmission System.

Hey our Transformer formula in action again!

This is how you pay for Power, you receive over the wires that are no thicker than your arm, that carry 250 Kilovolts, then get stepped-down to the split-phase 240 Volts AC that then splits out in your ASC breaker panel into two 120VAC rails. This is another great subject to learn about. How to properly understand the role of each wire that connects to your Duplex Outlet. You would be amazed at how many people will take a Vintage Tube amp, damage the unit by installing an IEC socket and then connecting the Safety Ground to the chassis.

Historical note: AC vs. DC was a huge fight between Edison (DC) and Tesla/Westinghouse (AC). Edison preached DC Power Transmission, Tesla was a fan of AC Power Transmission, and we all know who won that battle. The reasons why are key to understanding Electricity and knowing cool things.

Now, we will discuss the Filament windings, then the High Voltage windings (often called Sections).

The typical Tube Amp Power Transformer has a HV Section from 200 to 800 Volts (it can be 2 wire or 3 wire known as Center Tapped) AC, 6.3 Volts AC (also 2 or 3 wires), and 5 Volts AC (same, these can also have a third wire).

The center tap wire on a 6.3 VAC filament section is of great benefit for Tube Amps and Preamps. It allows the 6.3 and or 12.6 VAC Filament Section to be connected to DC Ground. This allows the reduction of Common Mode noise and also, if necessary allows a simple means to "float the filaments" with DC voltage on Totem Pole Tube Gain Circuits. This is yet another little piece of knowledge, remember the Law of Superposition? Hard at work again here. Look it up, it is a cool piece of information.

Manufacturers also make have some different sections if they design for DC on the tube filaments, and this is more common on Tube Preamps, to have a 12.6 Volt AC section, or maybe a 20VAC section (as in the Scott LC-21). These can be rectified and produce DC for the Preamp Tube Filaments, it lowers noise. But... at the price or the polarization of the filaments, causing them to wear out 10% faster. This is another curious aspect of Tube Filaments operating on DC current. Look it up, another small piece of Tube wisdom. A philosopher once said "seek and you shall find", in my Spanish "el que busca, encuentra".

Enough on Filaments, only to close this out by stating that you want to avoid over dimensioning Tube Filament Transformer sections.

If you need 3 amps of AC filament current at 6.3 VAC, get a 3 ampere, 6.3 VAC section. Headroom works against parking your tubes at the proper quiescent AC filament voltage. If you believe that a 6 ampere, 6.3 VAC filament section will work better with a 3 ampere load, think again. This is a very important DIY tip that took me years to learn through the school of hard-knocks!

Now lets talk about the High Voltage part, that is probably where most of the Hypertension issues manifest themselves.

The HV DC current (milliamperes of AC) are produced from across the High Voltage Plate Winding section on the secondary and will almost always have somewhat thin wires, as the gauges required for 250 to 500 Volts AC at milliamps of current are thinner than Filament wires, and usually the case rather than the exception. Unless the Secondary HV winding is providing more than 350 milliamps or greater, unusual for any Tube Amp, save for the Dynaco MK6 with defunct 8417 Power Tubes R.I.P.

Now, we move on to winding ratios and the formula, also important as it allows one to determine an un-labeled Power Transformer winding ratio, and also the impedances of any "mystery" Output transformer, such as a rare Output Transformer with "no labeling" that you are salivating to use on a DIY application. Output Transformers are the most critical component in a Push Pull Transformer Coupled amp, but that is a subject I discuss in other parts of my website.

Basic Transformer Formula #2

Vp/Vs = N1/N2

Where V = Voltage, N = Turns

Note: A "Turn" is counted as one 360 degree winding across a laminated transformer or toroid magnetic core.

We also have an  impedance "version" of this type of formula that allows one to use a Sine Wave Signal Generator, plus an Oscilloscope, to empirically work-out the "Primary and Secondary" impedances of Output Transformers when they are not published or labeled. The Power Rating is calculated from the size of the core itself, that is more involved, and I will not go into that interesting tangent.

 

Basic Transformer Formula #3

 (Vp/Vs)2=(Np/Ns)2=Zp/Zs

But I diverge here, as an Electrical Engineer I have these formulas burned into my mind, after all, 35 years of Engineering does that, it makes us Geeks start from the basics in College, and then, apply the heck out of these in the real world.

The Tube Whisperer believes that any Wise man, armed with the knowledge of Mathematics, can always understand Matter, Space and Time through Science.

Now we discuss the High Voltage secondary Power Transformer section further and how this can get boosted and hurt your Tubes.

In most Tube Amp Power transformers, the secondary HV plate winding voltages are greater than the primary voltage, or equal to (e.g.. maybe for voltage doubler applications?) look this up, there are also ways to triple the voltages. The penalty is that it halves or thirds the current capacity...

Hence and this is all a mathematical thing, when you take a ratio of Primary to Secondary windings and work some numbers, the design center voltages on a Power Transformer will have two values given;

No Load = the resulting AC voltage measured when the transformer section is not connected to anything.

Full Load = the resulting AC voltage measured when the transformer section is delivering the full rated current.

I previously stated that the key to good and safe "Un-regulated" Tube Power Supply design, is to always load Tube Filaments @ no less than 80% of the Full Load Current rating, or ideally, at the published Full Load specification. DIY tip!

This is a Audio Rodent belief that if you use a 6 amp Transformer on a 1 amp Filament Load is better.

Here the unlikely reality that goes against the "tweaker mentality" and gets well meaning DIY enthusiasts into Tube Hypertension, if you paid for 3 amps AC, you need to use the 3 amps AC. More here, is never better for Tube Filaments.

Now this is not the case on the High Voltage section, here we need to consider 'headroom' as part of the normal load and operation, this goes with the Tweaker Mentality, part of the laws of chance and assumptions.

Now loading a HV AC Transformer secondary to 100% will result is a Power Supply that does not sound good, there is no margin, and the DC High Voltage will experience sags. Voltage sagging is something we want to avoid in HiFi Tube Amps, but may be a interesting "tone-affecting" feature in a Tube Guitar/Bass amp.

The HV section that creates the 200 to 525 Volts DC after it is rectified, is usually happy at 65 to 75% of full load. It is never a wise design and load the HV High Voltage Transformer Section at full load, this means Heat, Trouble and Voltage Sag.

Again the High Voltage section requires "headroom" to properly give your amplifier or preamplifier the necessary steady state DC voltages that the tubes require and keep the Power Transformer from overheating. Keeps the Plate Voltages steady from wandering when the tubes crank up Also Sprach Zarathustra!!

Now if you end up with too much DC voltage, you have either "over-dimensioned" the Power Transformer Secondary HV section capacity, or need to drop some of the extra DC volts across a DC Choke, or Power Resistor or both.

If you have to drop more than 30 to 50 Volts, you probably need to re-think your HV design. But I digress, as I am talking about Tube Amp Design here, and I want to explain Tube Amp Hypertension, and this is not really about how to size a Power Transformer. I am working on my first Tube Amp Book, to be published in 2022-2023 to take people who want to get into building amps to the level they need to enjoy good results.

My knowledge is so useful, to be able to follow what happens in Vintage Amps operating at 125 VAC that I included this here as something good to know. When you decide to build DIY, this is all critical information.

So.. about the Filaments again...

The AC voltage to your precious and expensive NOS Telefunken or Bugle Boy Tube Filaments, should settle near the 6.3VAC or 12.6VAC, and stay at or within a +/- 5% value, you are fine, and your $wallet$ is safe.

This is quite straightforward for modern current production units and almost always taken care of by the designer.

But, on a Vintage Power Transformer, it can, when a 115VAC Primary is connected to 120-125VAC significantly boost all of the AC secondary voltages, not only to the tube filaments, but the HV section as well, causing overheating, super hot tubes, filaments that look like small light bulbs, tubes making noises as they heat-up into "over-heat" steady state. These are all the tell-tale signs of discolored artwork lettering on Tubes.

If your tube amp filaments are providing illumination to a dark room, something is off and wrong.

Folks these are filaments, not Light Bulbs, although they are very similar in their fundamental design.

When over-heated, some Power Tube lettering will change color from Red to Orange.

As in JJ Tube lettering, and I love how JJ's sound BTW, they are probably the best value in tubes today.

The other acid test of Vintage Tube Amp Hypertension diagnosis is to allow your Vintage Tube Amplifier or Preamplifier a warm-up time of 15 to 30 minutes.

Then, try to hold the palm of your "bare hand" on the top of the Power Transformer.

If you cannot hold your hand there for at least 10 seconds, without pain, you are killing your tubes and making the tube sellers very, very happy people.

You are probably in that Frequent Buyer Program, funded by Audio Forums and have a great solid "return customer" profile and likely complaining that tubes just don't last.

Not to even mention those tired and worn out Electrolytic Capacitors that you just cannot get yourself to update as you fear that your equipment will lose value, ridiculous indeed.

That expensive $45.00 Metal Can FP type Electrolytic replacement capacitor that you cannot afford, and is sorely needed by that "Un-Molested" equipment.

We now have a safety situation of a 35 to 75 and even 80 year old Power Supply capacitor that is dry of Electrolyte. And this Capacitor is now operating at or above it's maximum DC voltage rating, and drawing DC current, and may blow a fuse, if you are lucky. Any Metal Can cap should never get even the slightest warm. If that Metal can cap is warm, it is leaking and drawing DC from the HV Power supply.

Unbeknownst to most, there is also Vintage Equipment "High Voltage Electrolytic and Coupling Capacitor "current creep" that does melt Power Transformer Secondary HV windings before any fuse will blow.

So make sure that you stop belief systems, and break out a calculator and a notepad. Stop believing those Forum rodents and shy away from EBay sellers who flaunt the "Unmolested equipment" narrative, they are, literally, playing with Fire.

Using "Un-Molested" Vintage Tube gear is a sure way to accomplish and achieve failure, while never, ever enjoying the full sonic potential of a 100% restored Vintage Amplifier or Preamplifier.

Imagine the Car restoration people driving their old cars with the most minimal change, they would be driving an Un-Molested 57' Chevy, happy that the car is all original except for the Battery. Then one day, the brakes fail and they crash. Was the value of this vehicle different when restored? Absolutely.

But the Vintage Tube Amp hobby is full of delusion, and the manifestation of this has a name, and this name is "Un-molested".

Old stuff sounds old, old parts are beyond lifespan, and old solder connections can behave like Low Pass Filters - (LPF), cutting off precious high frequencies, delivering that vintage muddy, old, idiosyncratic tube sound that hundreds of Dynaco PAS users seem to enjoy? I just really don't get this.

I can totally understand paying for a 100% original PAS2/3 Preamplifier to put on a shelf and not use it. To own as an antique, not to be operated. This is where "Un-Molested" makes total sense. In museums and large collections of non-operations electronics. This is a cool thing, just don't dare to plug them in a turn them on.

Every time I see those EBay photos of Vintage equipment, old capacitors, old carbon resistors and the Green Selenium Rectifiers, I just shake my head. I just cannot understand how people will pay $800 for an Un-Molested Preamp when a fully and lovingly restored unit loses all value, no bids!

The bizarre world of belief and perception hard at work for collectors and well meaning but confused buyers.

You cannot even start to believe me until you actually take any 100% stock original amp and test it.

Yes, Test Equipment, that inconvenient part of the perception game, that calls on fools at the worst possible moments when smoke gets in your eyes, tube amp smoke that is, not the song. Although it may happen simultaneously!

Ever wonder how that "Un-Molested" group of Vintage Hi-Fi lovers, may never hear the full potential of their vintage gear, as they lust after that fuzzy, soft, rolled-off sound. They even start to get used to bad sound, and when they hear a restored amp with new tubes, they claim it sounds "strident", "bright", "like Solid State", well this is called High Fidelity.

In the realm of "Un-Molested" Vintage Equipment we have here the host of pre-existing Vintage Tube Amp symptoms:

>Huge channel to channel imbalances, old Balance Controls are pretty much shot, an old $1.00 part holding the music hostage to a belief.

>Really bad Volume controls that are way out, and I mean way off. The resistive carbon wafers often measure 30% different. Just use a dual channel oscilloscope to compare Left/Right Channels, sobering Oscilloscope traces.

>Huge differences in out of tolerance Capacitors and Resistors. The ignored Dynaco PAS Channel Mode and Width Selector Switch. Here we lose 50% of the glory of the PAS2/3. The Carbon Resistors can be tens of Kilo-ohms out, and these resistors are critical in value, and work in tandem and collaboration with the "Un-Obtainable" 750K PAS Balance Control. When these resistors measure differently, the Dynaco will not image and the channel separation is dramatically degraded.

>Then we have unhappy audio session visitors, and people, just too polite to tell these owners that the equipment sounds like shit.

Now there is one "band-aid" solution to all of what I state above, to lay out some hard cash for a high quality 10 ampere VARIAC to operate your pristine old, un-molested Marantz 9's.

If you really believe, that your Vintage Amps sound better left "un-molested", be my guest, and feed it what it needs from a Variac, start at 110 to 115 VAC and enjoy the fuzz and all of the Vintage Amp beliefs and update your Insurance Policy.

I will always issue challenges to the "Un-Molested" cult., always.

Dare them to connect their gear to a Signal Generator and an Oscilloscope, and witness what is really happening to the music.

When audio beliefs do not allow one to touch anything, and keep Selenium rectifiers and Dry/Leaky Power Supply and Coupling capacitors that they hope will "reform", then a VARIAC is the only thing that can save your vintage pieces from reality, and your house from a Fire.

This way, you can safely dial down the AC RMS voltage from your AC wall outlet down to 115VAC or 117VAC and make your vintage amp play, but never safer. Never, ever leave any original un-molested vintage equipment alone, and powered up. Only get up for the Bathroom or another Soda.

Now.. once your equipment gets the magic wand, you will immediately notice that the amp gets better Bass, the noise floor drops down, and the tubes don't make the noises of slow death, the filaments glow with joy and that Tweeter hiss, is now far less.

You will also note a drop in the pesky 120 Hz Power supply buzz, it drops down to where you actually need to put your ear up against the speakers. You will NEVER EVER have a noise free Tube Amp. But you can lower the noise floor to such levels that are imperceptible from your listening position (sofa or favorite chair/beanbag).

But when you don't upgrade your old gear, and connect it to 2021 AC Wall Voltages, your precious Tubes are living with "Vintage Amp Hypertension Denial" their "voltage pressures" are in the Yellow to Red ranges and the current rises, taking out what little life they had to start with.

If you take your RMS AC Voltmeter and carefully measure the AC loaded voltage across the filaments, and expect to read 6.3VAC, you may be shocked (no pun intended) that your meter reads 7.5 to 8.0 Volts AC RMS.

One sure audible sign of overloaded filaments is, that loud musical passages sound overwhelmingly HUGE.

As if someone is turning the Bass control to Max when the music goes to from Mezzo Piano to Forte and back down, this is a non-linearity effect created when there are more free electrons emitted by the filament being sucked up by the plate when the music swings hard.

Filament voltage control is a critical ASPECT of High Fidelity in Tube Audio Circuits. Ignore and just order more tubes... at your own $$.

Also Vintage Amp Hypertension will increase DC voltages to the Power Supply Capacitor sections and these can 20% to 30% higher, ouch.

Just read about that stock ST-70 FP Electrolytic Capacitor "first section" and please understand it.

And never dare to power up a Vintage Amp with No Tubes in the sockets, the DC voltage will be dramatically higher and unless your first capacitor is rated at 600 Volts DC.

Also never dare to feed a Tube Rectifier Power supply with anything less than 60% of the AC Mains Voltage, doing this will cut the life of the rectifier as the 5V Filament is starved and the High Voltage is asking for electrons it does not have available. The silence of the tubes..... the Whisperer listens.

This my readers, this is "Tube Hypertension-101" explained in my best Layman's terms for those who fear Calculators and Formulas, or may have a case of "Vintage Equipment Nervosa".

These and many of the reasons why you keep having to replace tubes every 3 to 6 months are laid bare and raw.

I am a Tube Whisperer, and do hear when any amp loses that "magic" and sounds flat.

When Tubes die out and fade away, or when brand new EL34's immediately get Red Plates right out of the box they came out of, something is off.

This my amigos, is the bane of the flat sound of new tubes in un-molested vintage gear. And when you leave these cults, and become an independent thinker, your High Fidelity experience will reach a new phase, a bright sunny day, better sound and spending more money of source material, better streaming sources and interesting tweaks for your music room.

So what can we do?

Well I am one who just will pull out and replace, if possible, the original old Power Transformer and use a new one that can connect to 125VAC and not even break into a sweat. Or I can try to modify the Power Supply, but with limited success.

If you absolutely prefer to keep the Vintage Power Transformer wound with a 115/117VAC primary, invest in a high quality Variac, or build yourself a Steroidal Balanced Power Transformer Box. If you are on the cheap side, and I have nothing against cheapskates, they also have rights, they can buy a Bucking Power Transformer box on EBay to lower the Primary Voltage down to 117VAC.

Parking Tube Amps and Preamps for optimal operation at 125VAC is my fundamental design criteria, then everything else falls into place!

This is especially true for and of Cathode Biased Tube Amplifiers, as these have no way to adjust the current through the Power Tubes.

So what are the benefits of a serious Vintage Amp upgrade?

>No transformer mechanical buzzing

>No overheating,

>None of that "lost magic" as your tubes now Bias-up with no fuss, and play well.

>Extra Cash, to help you score that nice Bordeaux Red for your next music lovers session

>Primary voltage control to 115/117 VAC, saving your tubes, and improving musicality.

After all this is why we love tubes, they are imperfect musical devices, able to make music in so many different ways, never twice the same.

But Tubes do need care and feeding, else you just replace tubes often and complain that Tube amps are too much of a hassle.

Tubes are like Orchids, they don't live long if you don't understand them.

BELOW ARE MY PERSONAL DESIGN GOALS FOR UN-REGULATED TUBE POWER SUPPLIES

The maximum AC Filament Voltages that I recommend should never exceed (+/- 10%), so let's do some math so it becomes clear what I am taking the effort to explain here.

6.3 VAC RMS x 0.1 = 0.63 VAC RMS

+Max Filament Voltage is 6.3 VAC RMS + 0.63 VAC RMS = 6.93 VAC RMS (Maximum AC Steady State)

So... 7.0 Volts AC RMS is the absolute "LIMIT" on any 6.3 VAC Tube Filament, exceed at your peril $$.

-Min 6.3 VAC RMS - 0.63 VAC RMS = 5.67 VAC RMS (Minimum AC Steady State)

I really suggest and prefer this specification to be no more than (+/- 5%)

6.3 VAC RMS x 0.05 = 0.315 VAC RMS

+Max 6.3 VAC RMS + 0.315 VAC RMS = 6.615 VAC RMS (AC Steady State Filament Voltage)

-Min 6.3 VAC RMS - 0.315 VAC RMS = 5.985 VAC RMS (AC Steady State Filament Voltage)

So now that we get the mathematical results for the Filaments, let's now examine what Vintage Power Transformer Tube Hypertension does to your Plate Voltage with an actual Case Study.

How this has a dramatic effect on all Tubes, all Power Supply Capacitors and Components, the Cathode Resistors and in general, the well being of any Vintage Tube amplifier or Preamplifier (a.k.a Dynaco ST70, EICO, Scott, Fisher,...... the list is very, very long) is sobering.

Let's make this one easy and free of Math, I can explain the concept better using a real amp.

SHERMANAUDIO CASE STUDY: THE DYNACO ST-35 "MANUFACTURED HYPERTENSION"

The first capacitor Section of the stock Dynaco ST-35 amp has a published specification based on a 120VAC Voltage.

So you may say, what's the big deal, 120VAC, easy.

The most I ever measure at home is 123.5 VAC, but this is where the deception hides, so what's the problem Sherman, explain this to me, are you obsessed?

I pull out of the Dynaco Manual a clip of the ST-35 DC Voltage Chart.

This chart is referenced to 120VAC on the PA774 primary, and if your amp is lucky, and your AC wall voltage is 118VAC or 120VAC and below.

And even at 120VAC your friendly factory vintage Dynaco Power Transformer PA774 is already sweating for one key issue, Dynaco over-dimensioned the HV Secondary, but why?

I really don't know why, but have a strong hunch it has to do with the 7189 Tube. I digress for a moment here about the 7189.

When this Tube was unleashed on the market, it was probably common for people to believe that a 7189 amplifier could use a 6BQ5/EL-84 as a substitute, wrong.

The truth is that an amp designed for 6BQ5/EL-84 can use a 7189, but this is a one way street. If you have an amp designed for 7189, a 6BQ5/EL-84 will perish, and in ways that fried quite a few Output Transformers. The Olson AM-224 is a case study of fried OPT's. I have two of them, one, has fried OPT's, the other actually made it's way to me before someone put EL84's into it.

So the ST-35 has the 7189 thing going and I suppose that original PA774 design was made to take advantage of the 7189 tube, and make the EL84 suffer enough pain to wear them out, but no quite kill them off immediately.

The manual makes NO MENTION of this, and I have un-masked Dynaco here. So all of you ST-35 owners out there, take heed, you have been Dynaco-ed!!

Now, make that PA774 primary voltage 123.5 VAC, a very common AC voltage that we have at homes across our nation. Now remember that transformer formula:

Well on the PA774, we are starting with a AC Secondary of 330-0-330 VAC, and this was a voltage selection intended to push the limits of the Maximum Plate Voltages of a standard EL-84/6BQ5, beyond the max, it was really wound for 7189's. and I will show why.

In reality, the Dynaco people most likely wanted people to enjoy this precious design using 7189 Tubes, that were readily available in 1968, but today if you need a 7189, you have to buy the Russian version 6n14pEB or pay $100 each for real 7189's.

Warning: the 7189A is not a 7189, it depends on how the tube socket was wired. The specs of the tubes are the same, but the pinout is slightly different so check before plugging in. Some manufacturers used the spare pins on a 7189 socket for solder tie points rare but possible.

I highly recommend that any ST-35 owner only use the Russian Tube, real EL84's just burn out too fast in the stock ST-35, but they do sound great as they pass away.

I have a small tube cemetery full of Mullard 5-20/EL34 and ST-35/EL84, and these are like spent Rifle Cartridges, when I was learning to shoot without knowledge back in the year 1996-2005, a time of Tube learning, Red Plates, Motor boating and lots of hard $lessons.

If we examine the ST-35 voltage chart below, and look at the bottom line, these are, from Left to Right the DC Voltages that should be measured with a VTVM (high impedance tube voltmeter), else what your trusty modern VOM will measure will likely be 5 volts lower due to meter circuit loading.

Just look at the Plate Voltage on Pin #7, 370 Volts DC!! Ouch. You need to subtract the Cathode Voltage from the Plate Measured voltage to calculate the actual Plate Voltage. So 370V - 13.5V = 356.5 Volts DC if the Dynaco ST-35 factory plate voltage value. Go to the EL-84 spec sheet, the Max Plate Voltage for an EL84/6BQ5 is 300 Volts. Dynaco is parking the 6BQ5's at 356.5 Volts a whopping 56.5 Volts over the published specifications.

This to me screams 7189 all over the place, and why I recommend using EL84M/7189 or the Russian 7189, makes sense, and holds up to the punishment.

These voltages are proof that the ST-35 was not an EL-84 amp but a 7189 amp with an EL84 disguise.

The (3) three Power Supply Capacitor HV voltages are suspect, and last one, is the Common Cathode Resistor voltage reading on a stock ST-35 FP Capacitor, now unobtainable, 13.5 VDC, more on this here...>>

If you take a stock ST-35, with the Stock or even a New Dynakit PA774, and carefully with one hand in your pocket, and the amp belly-up, with meter ground Lead clipped to DC Ground, tell me what you measure?

My "Cover" ST-35 was measuring +420 VDC on the first PSU Capacitor, yes folks not +380 VDC, so what was happening here?

Well, for one, the secondary windings of the stock PA774 and the new replacement PA774's are wound to 120VAC and a ridiculous 330-0-330 VAC.

I am connected to 123 VAC, sound familiar, measure familiar, Hypertension? Yes.

This is not a conspiracy to sell more tubes and lower distortion, it is just bad Dynaco design, intended to push the bias on the Tubes to achieve an unreasonable Power and Distortion specification, the Solid State tube amp complex.

Dynaco seemed to have been competing with Solid State, in the Tube heyday. So the solution was to crank up the voltages and currents on the tubes, to compete with the "lower transistor distortion specifications", happened in the best of families.

Yes my friends, Hype is not modern, it creeps along the ages.

I am not sure why Dynaco wound the HV secondary up to this extra 30 Volts AC per side, but I have solved this problem. I replaced the PA774 by using a Hammond 272FX with 300-0-300 VAC.

But will the 272FX fit the stock ST-35? Unlikely, Dynaco chose to make this amp small, to give it Tube Amp Curb appeal.

I haven't one on hand to try, heck I may ask Hammond to make one that fits.... (a future Transformer Project in the backburner).

I even asked one of the PA774 sellers, if I could order a PA774 with a 125VAC primary.

The answer was "so you have a voltage problem?"...... (sigh), the answer was No I don't, everyone else does!

All we need is for the folks who so lovingly re-create Dynaco Power Transformers to FIX these problems, not just throw them over the fence just duplicate the original windings.

STOP, please STOP, wind the primaries for 125VAC, save the planet, save the tubes, save the Music.

On a side note, the same issue happens with the Mullard 5-20 Amplifier, the stock Mains Transformer is way over dimensioned in the Mullard Book and a real EL34 Slayer. You can read about this saga of mine in my "Hand Made Amps" section and how I learned about "Tube Amp Hypertension" the hard $$ way.

Refer to ST-35 "Stock" Voltage Chart Below:

So... if the +385VDC is now reading +410-420VDC, the rest of the ST-35 amplifier is also boosted?

ST-35 Published Voltage Table

 

Hence even the Cathode Resistor DC voltage read 17 Volts on my VOM, and this my fellow Tube lovers is a  Vintage Tube Amplifier Hypertension diagnosis.

The Maximum Plate Voltage and Plate dissipation of an EL84/6BQ5 tube is published in the RCA Tube Manual:

These are the nominal values, and some of the specs can be exceeded, but never the Max Plate Dissipation, never, but if you like Red Plates, be my guest

Pin #7 on the 6BQ5/EL-84 Plate connection and the voltages in this chart above, are referenced to Ground, this makes a difference in the math when you calculate the Plate Dissipation, you have to subtract the Cathode potential voltage from the Ground referenced Plate Voltage, or you need to place the negative of your VOM on the EL-84 Cathode Pin and the Positive lead on the Plate Voltage Pin. This here is a common mistake made by even seasoned Technicians, believe me, I made the same mistakes. Its all part of being honest and willing to grow and accept/admit mistakes.

Those who never admit to making a mistake, live their lives within a mistake.

So we are informed by Dynaco, in DC Voltage this chart, that the actual plate voltage on the EL84/6BQ5 is by inspection:

+370 VDC - +13.5 VDC (Cathode Resistor Voltage Drop) = +356.5 VDC.

Does +356.5 VDC = +300 VDC from the EL84 Max Plate Voltage spec sheet? No.

Hummmm, we have some of that funky vintage "spec game" tube stuff going on here.

The ST-35 Cathode Resistor is 95 Ohms, so we can now calculate from the ST-35 Voltage Chart the Cathode Current from the table.

Ik = 13.5 VDC / 95 Ohms = 142.1 milliamps (this is 4 tubes as the resistor is common to all)

So we divide 142.1 milliamps / 4 Tubes = 35.5 Milliamps per EL-84/6BQ5 Power Tube.

So when we calculate the quiescent Plate Dissipation on the ST-35 Power Tubes:

P = V * I = 356.5 Volts DC * 0.0355 A = 12.65 Watts, another OUCH from the folks at Dynaco, at least they dared to publish these measurements.

Now does 12.65 Watts = 12 Watts? No.

Conclusion:

The stock Dynaco ST-35 is a EL84/6BQ5 tube gobbler, and really requires the 7189, so your amp will likely eat up your EL-84's in a matter of weeks or a month.

From the RCA-30 Tube Manual the 7189 Tube specs are:

250Volts AC and 48 milliamps and this equals 12 Watts.

But we don't have 250 Volts in the ST-35 we have 356.5 Volts and 35.3 Milliamps and exceed the Plate Dissipation by 0.65 Watts.

The 6BQ5/EL84 max values are at 300 Volts DC while the 7189 can handle up to 400 Volts DC on the plates, a different tube, way more robust than the EL-84/6BQ5.

This made amps, designed for 7189, literally go into Power Tube runaway current when a lowly innocent EL84/6BQ5 was substituted by your friendly Tube Substitution manual and even the Instruction Manuals!

Sending customers to the Tube Stores on a regular basis if their 7189 amps even survived.

The EL-84 will sound glorious in a 7189 amp, then the EL84's will die or the Output Transformer Primary will melt.

After 10 minutes the EL-84/6BQ5 Plates will glow red, the music will sound flat, and maybe the amp will start to Hum if you are lucky.

The ST-35 amplifier was really designed to work optimally with the 7189 Tube as it came from the factory, and can work with EL84/6BQ5 with the Transformer Primary dialed-down to 115VAC with a Variac.

To park this amp is a "safe zone" you need to calculate the properly corrected DC Plate Voltage.

So if we have 12 Watts Plate dissipation MAX, and we like the music to sound correct, lets park the tubes at 35.5 milliamps.

Therefore the proper maximum Plate Voltage for the EL84 is 12 Watts = Vp * 0.035

so Vp = 12 Watts /0.0355 amps = 338 Volts DC.

Does 356.5 Volts DC = 338 Volts DC? No

Granted, the EL-84 can always take a higher plate voltage than the published specifications just as long as we DO NOT exceed the Plate Power Dissipation of 12 Watts.

ST-35 Case Study Conclusion:

Dynaco execution had Audio performance high on the feature list, but the compromise was the parts vs. cost conundrum.

Dynaco chose to use Diodes on the ST-35, and this was a wimpy decision, including the fact that the original Dynaco Plate and Filament Power Transformers ran HOT back then, and today, you cannot hold your hand on them for more than a few seconds after the pain reaches your brain.

Dynaco kept costs low, they kept prices low, margins high and the results today really require the use of a high quality VARIAC to operate these ST-35 amps with 6BQ5/EL-84's in stock vintage form.

On a separate subject if you compare the prices of these kits nowadays in today's dollars, they were not a bargain in any sense back then. But today most folks haven't moved their price compass, and believe that a $500 component, or a $1000 Tube are exorbitantly expensive. These are actually bargain prices.

But you ask someone today to pay $1000 for a Tube Amp and they would rather pay $1000 for an iPhone or a Macbook Air, so fair enough.

But I do have one thing I must state about Dynaco, they wound among the absolute finest Output Transformers in the market, their frequency response is still breathtaking today and the winding techniques difficult to duplicate. These were at times wound by hand, by people who blurred the boundaries of science, technique and art.

My impression of the stock ST-35 Amplifier was always to be worried Power Supply Diode "Plate Voltage" slam, slowly hitting the ST-35 Tubes with H.V. before they warmed up, creating Plate Electron Stripping. This caused the tubes to die a faster death.

This is probably akin to our "Sugar addicted" society that consumes ridiculous amounts of Carbs, Sugars and Junk Food and complain that they can't lose weight and exercise like mad.

I always thought that a nice 5AR4 Rectifier Tube with the slow turn on, would have been a better long term solution, but the cost...... $$$, I chose the 5AR5 and Hammons 272FX, the ST-35 sounds simply spectacular, relaxed, musical, even bordering on mystical. And this is with the new Z-565 Output Transformers from Dynakit Parts. These are amazing! I would order 20 pairs if I had the funds... to make some ST-35's for sale...

The final piece.... Diode Tube Slam.

Yes Solid State rectification is great, but it is another bandit in the Vintage Amp Hypertension issue another silent "Tube Killer".

So, I decided to pull out the Dynakit PA-774 Power Transformer and sell it as I needed a 5V filament section. The Hammond 272FX was the perfect choice, although I am not sure it will fit a stock ST-35, I sold my ST-35 years ago when I was cash strapped (darn).

What I did next, could go against common convention, but I decided to replace the ST-35 Diodes in the Power Supply with a Tube Rectifier and OMG, wow!

Yes a 5AR4 Tube Rectifier upgrade, slow turn on, wonderfully tight Bass.

A good basic secondary ST-35 Voltage is 300-0-300 VAC with a primary of 125 VAC.

I also use a C354 Choke in place of the 50 Ohm Resistor, why not?

The 272FX 125VAC tap is the worry free selection, and I use a SPDT switch to go between 115 VAC and  125 VASC, and the safer one to choose and park the amp in a comfortable place is the 125 VAC. The amp will work at 115 VAC but only when your Mains is 115-117VAC. At 120 VAC the 125 VAC primary is the best choice.

I always like to park Cathode Resistor (self-bias) about 5% below the schematic or published DC voltages, it is the safe zone.

The 272FX offers this unique 115/125V Primary that is just awesome of Hammond to listen to the DIY Tube community and respond with this option.

I have written many pages on the realities of Un-Regulated Tube Power Supplies, so I will not go into this here, you can find these rants throughout my website.

Here is my Dynaco cover ST-35, and it sounds MARVELOUS.

The plate voltage is 15 volts below the published spec and I am thrilled, the Hammond 272FX does not get HOT like the PA774.

The bias board allows me to park the quiescent current through the EL84's at different levels, and I will be experimenting for the optimal place.

Here is the result, and I am loving this with my Dynaco PAS3x, that I also updated and is sounding fantastic.

UNREGULATED TUBE AMP DC - GOOD TO KNOW STUFF

YOU MAY NOT HAVE ANY ISSUES WITH HIGH MAINS

BUT...... LIKE HIGH BLOOD PRESSURE, HAVE YOU TAKEN SOME READINGS LATELY?

2011 was a year that has me in a life/career transition. Having moved away from the Caribbean in late 2010 after 15 years the roots are still not in place. My shop area is still in a transition and projects have been delayed.

But I can share thought's and ideas......

SUBJECT: VINTAGE AMPLIFIER AC VOLTAGE CORRECTION or ADAPTATION

Voltage correcting transformers are a must to effectively manage the tube life and performance of Vintage Amps.

Not many people understand how un-regulated power supplies work. This is a key understanding in owning Vintage Tube amps.

It is a fact that any odorous and dusty old tube amp will work best when connected to a 115 to 118 VAC mains. Power Transformers of 40-50 years ago were manufactured based on a 117 VAC primary voltage, so the turns ratio was in fact making the correct secondary voltages when connected to 117 VAC.

If you want to compare your voltage readings on that old ST-70, ST-30, A500, A700, Fisher 400 or Marantz 7 you needs to have a Variac and set the primary voltage to the one that is published on the schematic.

The problem we face today is that Primary AC voltages in the range of 115 to 118 VAC are not very common today. Unless one happens to live very far from the power station, in the Styx, you will probably not measure 125 VAC with your VOM, but 120V or 119V.

Now connect that old Dynaco ST-70 to 125 VAC and you will immediately exceed the DC voltage rating of the first section of that Un-Molested stock Metal Can Quad Electrolytic FP capacitor, not to mention AC and DC voltages sometimes 20 to 25 % above nominal, I have seen 30% in some old Stromberg Carlson amps I own.

In order to appreciate what I am saying here, one must understand that Power Companies always prefers to err on the high side when delivering commercial power.

Meaning that less Power Loss = I2 x R, means less power lost on the electrical lines, more profit, less loss as heat when we buy juice from them for our homes.

But ..... today's 125 VAC mains does not work well with most old tube amps, unless some method of voltage control is used, or the design itself provides a 120 VAC tap.

Most vintage tube amp designers happened to make their quiescent points in the upper half of the input AC voltage range, designing some headroom for the rise in AC mains voltages.

But not all did, and we shorten the life of our tubes when we connect old equipment directly to the power grid without measuring with a DC VOM meter.

If you don't believe me, you need to measure the voltages and currents on your vintage tube amp and compare them to the original values shown on the schematic to understand what "High Mains" AC does to your precious tubes.

Also the AC Filament voltages will often rise above the 10% maximum allowed and dramatically shorten tube life. When you operate a 6.3Volt Filament at 7.5Volts, ouch!

Most current production tube amps do not have this problem, as their transformer primaries are wound for 120 VAC and the voltages settle down quite nicely.

But amps built from the late 40's up to the mid 70's have some issues as their Power Transformers primaries were using the 115 VAC standard, obsolete in today's un-regulated power supply designs but still commonly used.

Regulated power supplies correct for this, but 99.99% of Vacuum Tube amps do not implement regulation. Some Tube Preamps do and in fact benefit from this. But regulating 485 VDC is not an economical thing to do, and would probably double the list price of any Tube Power amplifier. Also the complexity and size of a regulated 500 VDC power supply is $$.

High AC Mains will make filaments wear out sooner. You know when this is happening, the tubes act like light bulbs and actually provide illumination is a dark room. When tube filaments are lighting up your room, they are actually screaming for help !

Remember that 6.3V and 12.6 V (DC or AC RMS) are the nominal voltages that the tube filaments require. The specifications will allow 10% over, meaning 6.3 VAC + 0.63 = 6.93 VAC.

But..... operate your tubes at 6.93 VAC and you shorten tube life.

This is a well known and scientifically proven fact that has been common knowledge since the late 50's. Wise designers operate tube filaments at the nominal value or 3% under.

There are a class of tubes that will suffer dramatically from high filament voltages, DHT Triodes.

These tubes have filaments that do not work well with high filament voltages.

The filaments on these tubes will draw proportionally more current as the voltage rises unlike a resistor whose behavior is defined by Ohms Law. In old radio's (I mean 1930's) 2A3 tubes actually had a rheostat in series with the tube filaments that allowed filament voltage adjustment over a specified range to adjust gain.

ONE DIY SOLUTION TO CLASSIC TUBE AMP HYPERTENSION

Build a "home brew" - Balanced Power Toroid - in a box, with a fuse and switch. Use a toroid that has 55-0-55 VAC on the secondary and the common but outdated 115 VAC on the primary.  This solution will shave off those extra volts and dramatically extend tube and amp life. Parts Express sells some toroid 800 VA that will work to power a tube amp.

Or you can use a 60-0-60 VAC toroid and 125 VAC primary. In any case the goal is to produce no more than 120 VAC to your amplifier, preferably 117 VAC.

In my modded Transcendent Balanced Power unit I replaced the 60-0-60 VAC Toroid with a 55-0-55 VAC keeping the same 115 VAC primary.

Un-loaded and connected to 125 VAC, the voltage I measure is 121 VAC-122 VAC.

As you load the transformer with equipment, the voltage will drop a few %.

The more you load the transformer secondary, the lower the settled voltage.

For instance, if you have a Dynaco Stereo 70 that will draw about 1.5 amps when powered up, this means about 180 VA of AC Power.

You can use a 500 VA Model so that it will load at less than 50% of it's total capacity, I would go with an 800 VA for extra headroom in case you want to connect a PAS3 Preamp as well.

The trick with voltage correcting transformers is not to load then past 50%.

1000 VA load at 500 VA (4 amps AC RMS continuous)

800 VA load at 400 VA (3 amps AC RMS continuous)

The 500 VA model is far more practical as you can also connect a Tube Preamp.

There are 625 VA, 800 VA and finally the 1000 VA models to choose from.

The benefits of Balanced Power operation are also realized here.

Any vintage tube amp will run cooler with lower AC Mains, the amp will sound better and you will be happier knowing that your vintage amp and precious tubes will last longer.

The side benefits of Balanced Power are lower radiated electrical fields from the AC Secondary cabling and quieter performance.

The link below will provide Toroid's for your project:

http://avellindberg.com/pdf/avel_y23_range.pdf

Here is the schematic of my "modded" Balanced Power unit, You can build one in any metal box that can be machined for the parts:

 

Order any one of the Toroid's in the 500VA to 1000VA range, depending on your application and build this into a small project box.

You will need to machine a mounting for a 120 VAC mono receptacle, usually a Greenlee Hole Punch, or your local machine shop can punch a correct diameter hole.

If you want to power a complete vintage tube amp/preamp/etc. system with an 8 Amp fuse, you need to order the 1000 VA Avel Lindberg Model [Y236954].

Maybe you can request that Transcendent Sound sell you the Balanced Power kit without the Toroid and you simply order the model that I show on the schematic. I haven't tried this yet, and my suggestions to Transcendent Sound were not well received. The suggestion was to use a bucking transformer on the primary. I don't see this as a solution but a fix to a problem with their design.

When I built the Balanced Power unit from Transcendent Sound I connected my amps to the unit (I had not even bothered to measure the secondary AC RMS voltage) and noticed that my amps were GLOWING BRIGHT  and the plates of the 6550 tubes were cherry red.

I measured the loaded secondary voltage on the stock design and my meter read 131 VAC.... yikes!!!

My plans in 2012 are to build a few "Vintage Tube Amp Savers" in stock for sale with the option to have an Analog or Digital meter on the front panel.

Here is the Balanced Power Unit, built inside of a discarded and gutted MASTR III GE Repeater Power Supply.

The courtesy AC Duplex was just perfect and so were the fuse holders.

 

Here is the inside of the unit. Avel-Lindberg 800 VA Toroid 115VAC Primary, 55-0-55 VAC Secondary, just perfect for Vintage Amps.

AC Output is around 121 VAC No Load and 115 VAC Full Load, but typically operates at 117 VAC for most of the time when the AC Mains

is around 123 VAC. No bucking transformers, just great innovation here and recycling old equipment.

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