Of my classic Vacuum Tube Audio Hobby
Check your Regulator & BC Vest
PRIOR TO ENTERING THE WATERS BELOW...
WHY CLASSIC TUBE AMPS?
Me? well I am all about Reliability & Restoration for safe, daily Tube Amp operation
Not appearances or aesthetics, although I try to restore Classic Gear for better looks when possible
My website is not one of the "Tubes for the rest of Us" open arms thing
My Website, is for Serious Hobbyists who Seek and Find......
Straight talk, Specifics, Facts and Humor
Technical subjects get Technical....
So I never just answer THE question....
"inform and educate"
Keep classic old equipment alive, for future generations
The past offers clues, so our future can be better
KNOWING YOUR PAST, WILL AVOID REPEATING IT
This journey, is about to get Technical
Are you ready for a deep read?
Coffee, Tea, Sharp Mind, Learning Cap
ON MY MATHEMATICAL RANTS
Math, oh Math, I really believe that the way that Math has been taught is not the best
When teaching Math, Teachers should show students real-life examples of how Math is applied.
A storyline of how Math is used, where and when
Trigonometry, Geometry, Algebra, Calculus, Differential Equations, Vector Analysis
Mathematical tools, are not a burden.
Each subject area in Math is just like a special "toolbox" with dozens of concepts that each
all do one thing very well...
Math models and describes our physical & theoretical reality in ways we can relate to
by Scientific measurements, data and the resulting solutions to all types of problems.
It wasn't until I took Engineering Courses to apply the Math, a light bulb turned on.
Word Problems get you thinking about the problem, not just the Math
So the next time you drive over a Bridge, think about the people who did all of the
Calculations, to make sure that it would not fall apart and have a useful service life.
So did your Trigonometry Math teacher ever show why you needed Cosine, Sine and Tangents?
Unlikely, unless You had a great Trigonometry teacher.
Same for Algebra and Calculus, the symbols mean more than Greek characters
They are life itself made into equations to help solve problems and understand the
world that we live on and in..
Me, I was terrible at Math. My scores were always close to failing.
WAS I GOOD AT MATH?
I needed special tutoring when I was in 1st and 2nd Grade
Could not Add or Subtract, so I would use my fingers under the desk like a Human Abacus.
Multiplication tables were sheer torture.
In Middle School I was terrible, in High School somewhat
good at Geometry, but struggled with Trigonometry and Algebra.
My Math Teacher and Soccer Coach Paul Trittschuh made Math bearable
with Humor, but missed the application part.
Then.... I studied Electrical Engineering.....
When I finally understood how to apply Math, the whole world
changed for the better, I now realized how to use the Unit Circle, take Derivatives
to calculate Position, Velocity and Acceleration...
Use Integrals to go backwards from Acceleration, to Velocity to Position.
A whole new world opened up.
Just as Tom Cruise told Brad Pitt;
"Now look at the world with your Vampire Eyes"
I saw a different world with my
Something about those "Decibels"
I use decibels often at work, and in this Hobby as well
My career is Radio and RF, so I use decibels alongside my Audio hobby
This is all deliberate, as the decibel shows us how versatile they are in a technical context
So what is a dB?
Well, lets start with two common formulas for expressing Power and Voltage in decibels.
POWER - Watts
dBw = 10 log (P1/P2) Power in Watts, Audio Amplifiers, RF Transmitters
Power is always 10 log
VOLTAGE - Volts
dBv = 20 log (V1/V2) Voltage in Volts, Audio Amplifiers and Preamplifiers
Voltages are always 20 log
Logarithms are also cool!
The log function is Log Base 10, not a Natural LOG, that LN is base e (Euler's Number) symbol is LN
Euler was a Swiss Scientist who created/ discovered the natural log.
Natural because it is used to describe the behavior of Nature, the Creation and also Money!
A QUICK REVIEW OF VOLTAGE AND POWER
WITH SOME ADDED CONTEXT
So Power in Audio is typically expressed in Watts, Milliwatts, not Microwatts or Picowatts
Microwatts and Picowatts are PC Board design level Semiconductor Dissipation levels
Millivolts, Microvolts and Nanovolts are usually in Radio Circuits, and/or Spectrum Analyzers
Watts P2 = 1.0w
(Audio Power Amplifiers and RF Transmitters)
Milliwatts P2 = 0.001w
(RF Cell Phone Transmitters and Circuits)
Voltage in what we use in Tube Amps is typically in Volts, Millivolts or Microvolts so some examples below;
Volts are the usual, Millivolts are used in RF Testing of RF Gain Stages, Microvolts are similar to dBm
they are used to measure and test the levels of received Radio Signals in a Radio Receiver
Volts V2 = 1.0v
(RF Transmitters & Tube Audio Amplifiers)
Millivolts V2 = 0.001v
(RF Receive and Transmit Pre Drivers & Audio Sources, RF Millivoltmeter probes to test/troubleshoot Radio PC Boards)
Microvolts V2 = 0.000001v (RF Received Radio Signals, RF Signal Generators)
The fear of Calculators, what are all those extra buttons for?
On your Calculator just look for a LOG key... if it is absent, don't worry for now...
It is unfortunate that we call those types of Calculators "Scientific" when they should be called
"Complete" and the usual Calculator a.k.a Adding Machine, "Normal".
I think that calling it a Scientific Calculator scares regular people away.
Now, the denominator in the dB formula is always your reference, it allows you to calculate
dBw = 10 log (P1/P2)
dBv = 20 log (V1/V2)
the ratio of two values of Power (P) or Voltage V), resulting in a ratio calculation
Then by using Logarithms and taking the LOG of that Ratio we make a dB
by multiplying the Power x 10 or the Voltage x 20
If you want to know why, Google is your friend...
A fraction has a Numerator and a Denominator
Fraction = Numerator (on top) /Denominator (on bottom)
Fraction = 1/2 = 0.5 = half
Fraction = 3/4 = three quarters
Fraction = e/Pi = (2.718281828/3.142857143) =0.864907869
Why did I divide Euler's Number by Pi?
Because I can... that is the Power of Math!
What is 0.86490 good for? Nothing really...unless it had a purpose.
You can do calculations for the Fun of it, just to practice
Just like Rappers Rap for the Fk of it and hope they got it recorded
And people shoot Bullets in the Forest at nothing really....
To have FUN
Egyptian Civil Engineers some 4500 years ago, used Pi, so why don't You?
They made some interesting structures with Pi.
If they used Pi, so can You!!!!
Pi is important to understanding A.C. Mathematics, Capacitors and Inductors...
Math is also symbolic, with little or no numbers.
f(t) = x (t) - y2(t) + z(t)
This is what makes Math tedious, the act of solving equations in isolation.
Getting a right answer, for what?
The missing link to Math anxiety, is calculating numbers without a purpose or a goal.
Just to pass an exam, but we should know why?
Every equation or types of equations should come with an image of what it represents.
And this is the missing link in Math Education today
Just my humble opinion....
Enter the Decibel or dB (applause please!)
That makes dB's user friendly when you get them as your data inputs.
If you only have dB's it's a simple addition and subtraction.
A First Grader can do dB calculations....
It gets more interesting when you have the units, like dBm and need to calculate an actual value of Voltage or Power.
Where the m stands for milli, or one thousandth of something, like 0.001, can you solve for the Numerator?
Sure you can, I will show how.
I will take you on an unexpected adventure to calculate Watts or Volts, Milliwatts or Millivolts, Microwatts or Microvolts...
The Metric System is perfect for all of this Math, and when you use dB's you are actually using the Metric System
Just like giving a Baby Cough Medicine, disguised as Cake!
If you insist on Inches, Feet, Miles, that's fine.
But when you start to work with Math... you realize that Calculations in Metric are so-much-simpler
and far-more-intuitive than English units, far more. All you need to do is move a decimal point Left or Right.
Just like you do when you reach in Intersection, you turn Left, Right or keep Straight.
Imagine having to do 1/8 of a turn on Intersection #1, then 3/4 of a turn on Intersection #2.
How many people would pass their Drivers License tests?
Life is Metric, then the English gave us half, then half of a half, then half of that half.
One Sixteenth, One Thirty Second, One Sixty Fourth.
Carpenters are amazing, they still use the English System, that is fine, until things get smaller than 1 Inch.
What is a dB reference value used for?
So the reference in the above dB formulas, is established by the denominator of the fraction;
P2 (Power) or V2 (Voltage)
Now to be able to calculate the actual value of the Voltage (Volts) or Power (Watts)
You are taking the Log of the ratio of one value to the reference value.
Then multiplying as: Power x 10 and Voltage x 20, look at the two formulas.
The Numerator, is that value you measure, estimate, imagine, etc.
When the Numerator is Greater than the Denominator you get GAIN.
When the Numerator is less than the Denominator you get LOSS.
Thus GAIN & LOSS are insights that the dB provides into what you are measuring or comparing.
Hence Mathematical Division is a "comparison" of two numbers, expressions, quantities, etc.
The denominator sets the calibration of the formula, establishes the unit of reference.
A Decibel alone as in 10 dB is qualitatively meaningless, unless you know what it is being referenced to.
But, the decibel is always quantitatively significant.
The decibel offers a "magnitude" or size of a measurement, so it can be used to know if it is a big or small thing
by just looking at the magnitude, you know that 10 dB is less than 30 dB. -15 dB is less than 5 dB, and so on.
The sign of the Decibel, it shows the GAIN or LOSS as a magnitude with relation to a reference.
The Numerator is known as the OUTPUT and the denominator as the INPUT or REFERENCE.
It can have two roles Mathematically, depends on how you use the Formula.
The more negative the -dB, the smaller the size of the value of the dB relative to the reference or denominator
The more positive the +dB value the larger the size of the value of the dB relative to the reference or denominator
If the Decibel is zero, that means that the measurement is equal to the reference, the same value.
Proof of reference Calculation
(zero Gain or Loss)
Input of 2 milliwatts (denominator) and Output is 2 milliwatts (numerator)
How many dB change is that?
dB = 10 log (2/2)
dB = 10 log (1)
dB = 10 * 0
dB = 0
Where the (log) in base 10 of one (1) is equal to zero, no change.
Put in layman's terms; if I measure a one Milliwatt signal and want to express than in dBm relative to 1 Milliwatt, this is zero dBm or dBm = 0
So Zero dBm means that my (1) Milliwatt signal in dBm is my reference, if you are working in dBm.
Example of a +3dB difference Calculation
(can also be called a "Gain", if Negative -3dB "Loss")
If you measure 2 milliwatts in your Circuit Output and your Input is 1 Milliwatt
this indicates (tells you) that your Circuit has a +3 dBm Gain when referenced to 1 Milliwatt.
dBm = 10 log (2/1)
dBm = 10 log (2)
dBm = 10 x 0.3
dBm = +3
dBm = +3, meaning that 2 milliwatts is twice 1 Milliwatt, +3dB higher than 1 Milliwatt.
If you measure 0.3 milliwatts in your Circuit Output and your Input is 1 Milliwatt
this indicates (tells you) that your Circuit has a +3 dBm Loss when referenced to 1 Milliwatt.
dBm = 10 log (.3/1)
dBm = 10 log (.3)
dBm = 10 x 0.3
dBm = -5.22
Your Circuit lost 5.22 dBm as your measured input was 1 Milliwatt and your measured output was 0.3 Milliwatts.
MATHEMATICS IS AWESOME
DON'T GET DISCOURAGED, SOME MATH TEACHERS LOVE MAKING STUDENTS SUFFER
DO NOT GIVE THEM THAT PLEASURE!
SHOW THEM YOU CAN DANCE, SIT DOWN, WORK OUT PROBLEMS
DISCUSS THEM WITH OTHER HOBBYSTS
USE YOUR TUBE AMPS TO TEST
ONCE YOU BECOME GOOD AT TEST EQUIPMENT AND MATHEMATICS
YOU CAN TURN THIS INTO A BUSINESS!
HANG IN THERE!!
Study hard, and challenge them to show you how to apply the Math they teach you!
Challenge your Teachers, show them who you are... that you are interested
Don't give up, Math is that best friend, who you don't invite over often...
as when it speaks, you feel uneasy, a bit disoriented.....
Math is a Universal Language
Music is a Universal Language
So when others ask how many Languages do you speak?
Not One, but Two
If you play an instrument or sing, Three.
I AM AN RF ENGINEER BY TRADE
DO YOU WANT TO LEARN ABOUT CELL PHONES?
A LESSON ON CELLULAR PHONES, (really Dude come on, leave me alone)
MAKING YOU WISER, AS YOU STARE AT THOSE SCREENS
AND MIGHT BE CURIOUS TO KNOW WHAT IS GOING ON
BETWEEN THE PHONE AND THE TOWER IN TERMS OF RF POWER
(SKIP THIS SECTION IF YOU FEEL QUEAZY, AND COME BACK WHEN READY)
CELLULAR RADIO AND THE MARKETING ON T.V.
JUST COME WITH US, WE HAVE THE BEST 5G COVERAGE!
So dB's inform you about the amounts of a thing or a measurement, in the previous examples were in milliwatts of dBm
what the dBm is being used for, is relative to a reference of 1 Milliwatt, any Cellular Radio Propagation Engineer knows the dBm.
The dBm is used in Cellular Coverage Map studies.
Those Marketing AT&T vs. T-Mobile Maps, the colors over the US are in dBm.
Just if you are curious when you see the Commercials on TV
Some picky Engineers use dBuV as well but usually the dBm is the universal GEEK code for Cell Coverage signal levels.
I got the Map below online. It looks highly like Marketeering material
The user density of the East users of the US is far greater than the West.
Can you sense some BS here?
I can see one thing, 5G is being deployed first in Dense Urban, so makes sense.
The East Coast area looks a bit light on Coverage, the West seems optimistic
A Cellular Signal above -110 dBm and that is quite weak, but usable, when you drop down to -111 to -118 dBm, that becomes shaky.
Good coverage is -85 dBm to -50 dBm, if you are -45 dBm you are probably less than a mile from the Cell Tower.
Remember 0 dBm, that is 1 Milliwatt. You will never see 0dBm on your Cell Phone as this type of RF Power
would require that you stand 3 meters from the Cell Tower Antenna and expose yourself to an RF Radiation Hazard.
The typical Cell Phone radiates no more than 600 Milliwatts of RF Power then it gets lost through your head, body, car, buildings, etc.
Now that you know the dBm formula you can calculate that in dBm of your iPhone Transmitter max power.
Cell Phones are measured in SAR (Specific Absorption Ratios) and is the maximum RF power allowed when exposed to human flesh.
Do Cell phones cause damage, of course, Coca-Cola causes damage, McDonald's causes damage.....
It is all how we manage the risks of the damage long term. So as we drink bottled water and ingest plastic molecules
we are walking around with Plastic in our bodies. How much of this can cause issues, the jury is still out.
How much damage can a Cell Phone cause, same, the jury is out on this as well.
I don't want to go deep into this subject but the link below are the current SAR limits.
SPECIFIC ABSORPTION RATIO (SAR)
THE MEASURE OF WHAT GOES INTO YOUR BRAIN/BODY
Back to the 600 Milliwatts;
dBm = 10 log (.6/1)
dBm = 10 log (0.6)
dBm = -2.21 dBm
So if your phone can RECEIVE -110 dBm, and Transmit with a Peak of -2.21 dBm you can see here MAJOR differences in Power.
Delta dBm = -2.21dBm - (-110 dBm) = 107.79 dBm of difference in signal level!
But remember that that -2.21 dBm has to travel miles to a Cell Tower, so when it arrives, it is more like -100 dBm or less.
And the farther you get from the Cell Tower, the lower the dBm until is reaches -115 dBm
and your call drops, or your phone roams for a better Tower
If you want to visualize how this works, just think about it this way.
THE CELL TOWER SCREAMS AT YOUR PHONE (-25 to -70 dBm) then continues to fade away with distance as you get farther.
YOUR PHONE WHISPERS BACK TO THE TOWER (-110 to -70 dBm) then fades away with distance as you get farther.
The Cell Tower has BIG EARS and a BIG MOUTH
Your Cell Phone has SMALL EARS and a QUIET VOICE
This is an "Un-Balanced" System that works
Below a diagram showing the Tower "Shouting" at the iPhone.
The RF signal has lots of enemies along the waym and that Tower is sending
out plenty of RF energy. Imagine that small iPhone with the exact
same obstables in "reverse" and transmissing only Milliwatts of Energy?
Remarkable that the Tower can even understand when the iPhone is Tramsmitting.
The Radio Signal Processing Power of today's 4G/5G systems is amazing.
Heck ebe GSM 2G and WCDMA 3G were cool in their days.
Just like Bell Bottoms and Mullet Haircuts...
But that is how it works, else you would have to carry a Trailer behind your Car with a
$200,000 Cell-on-wheels, to match what those Towers are doing!
Little do folks know that the old Bag Phones and Car Cell Phones developed 3 Watts (not 0.6 watts)
Back in those days, Cell Phones were quite big and they did not last very long on Batteries.
Having a small Pigtail Antenna on your Vehicle was a Status Symbol, like Pagers
until Drug Dealers started to use Pagers and we went from being a Doctor to a Thug.
A BALANCED SYSTEM YOU HEAR ME I HEAR YOU
The RF Engineer designs Coverage for a Balanced System, meaning that the RF Power that the Tower sends out
must be in Balance with your iPhone by making the Receivers at the Tower as sensitive as possible.
Else, your iPhone would receive the Tower, but the Tower could not receive your weak signal.
Radio Engineers call this an Unbalanced System.
It's a two way radio energy street in the sky where;
TOWER SHOUTS AT YOU WITH HIGH POWER THEN SIMULTANEOUSLY
UNDERSTAND YOUR WHISPERS AT LOW POWER
This is why Cell Tower Receivers are super sensitive and use sophisticated multiple Receive Antenna systems to hear your phones
that Whisper at much lower Power, much less, as the 600 Milliwatts is just the Transmitter in your iPhone (or some close value)
By the time that small amount of power leaves your iPhone it has to face losses in the phone's internal Filtering and Antenna SWR
so the power starts to fade quickly inside of the phone and then when the phone radiates that power
fades away as the inverse of the distance to the Tower, starts high, drops low.
Cell Tower Transmitters are usually in the +50 Watt Range, they need to travel through lossy filtering
and then, lossy Coaxial Cable that can lose on the order of -2dB to -5 dB, or more of the power in the lines themselves.
Of course the longer the Coax Cable, the more the loss. Runs of 250 feet are not uncommon and Higher Frequencies, more losses all around.
The Tower Antennas, they Transmit only the RF energy that makes it to the Antenna Connector from the Base Station.
These coaxial cable losses are now higher as frequencies are much higher in 5G than 4G.
But ironically 4G-LTE used the 700 MHz Band. but 5G NR enjoys 600 MHz, lower frequency, more coverage.
But the rest of 5G NR can go far above 2 GHz.
Newer generation Cellular Radio System Base Stations place the Transmitter right next to the Antenna on the Tower.
These are called "Main-Remote" Radio Base Stations, I call them practical, as the Coax Cable is just a 10 ft. Jumper, not 200 ft.
Public Safety Radio Systems, still use traditional long Coax Cable length's with all of the Radio Gear, the manufacturers
do not find enough funding to transform their infrastructure for smaller physical space and footprints.
Public Safety Radio Systems need temperature controlled shelters usually at the base of the Tower.
While some Cell Towers use Outdoor Cabinets only next to the Tower, super space efficient.
NOISE FLOOR, CAN I HEAR YOUR WHISPERS IN THE NOISE?
The Noise Floor in dB of a major US City is in the -100 dBm if lucky, while that Prepper Cabin in the Woods
that takes 5 hours to drive to and has no Cell Tower Coverage, that place can have a Radio Noise Floor below -122 dBm.
The limits of today's modern DSP receivers is -120 dBm, so as long as the Noise Floor is below -120 dBm, the receiver can receive.
Receivers are only as good as the Noise Floor, as You are only as good as the noise in a Bar full of people.
Picture yourself in a noisy Bar with a Band playing trying to listen to that "gorgeous lady" you just met
Over all of the Music and the Noise, you struggle to understand the words among the noise.
This is what a Cellular Site Receiver has to deal with, smack in the middle of for example; New York City.
Cell Phone Systems have enemies like Noise, Interference and Obstacles like Buildings, Trees, etc.
This takes proper Engineering to calibrate the Cell Tower to work as good as it can in Noise.
decibels are absolutely used in Noise Floor Measurements and Tower Top Receive Amplifier Calculations.
Tower Top Receivers also have internal Noise known as the NF = Noise Figure.
And as expected Noises are all additive to some degree as long as there are many simultaneous signals present.
BOSE Noise cancelling Headphones, they analyze the Noise around you and a circuit creates
a 180 Degree Noise signal and they cancel out, leaving you in blissful silence around the screaming kids, of the drone
of the Airliner Engines....
NOW YOU CAN GET A PICTURE OF HOW DECIBELS ARE APPLIED IN RADIO
THERE ARE GAINS AND LOSSES.... PLUS AND MINUS, GOOD AND BAD
RADIO IS PRACTICAL, WE ALL DEPEND ON RADIO SO OUR CELL PHONES CAN WORK!
Now, commit these three DECIBEL dB rules of thumb to your "Membrane"...
It makes You, a Visual Mathematician, not a just a Rapper, a Radio Rapper!
You can Rap about dBm and Signal Levels!
Math will always squash Rap
But Rap seems to always win over Math
As we have less STEM students today
(now how about that, and you sucked at Math...)
Being Cool is about being Smart
Just think about what career you want
Fast Money or Health & Balance?
I think it is better to Fade Away than to Burn Out (my opinion)
THE THREE DECIBEL THING ALL ENGINEERS SHOULD KNOW
#1 NUMBER ONE
+3dB = x2, or twice
then it follows that -3dB is half the amount.
(If I have a 10 Watt Amplifier, if I raise the Gain by 3 dB. I have = 20 Watts)
(If I have 100 watts and lose -3dB = 50 Watts)
#2 NUMBER TWO
+6dB = x4, or four times
then it follows that -6dB is a quarter of the amount.
(If I have a +6dB Antenna and my Transmitter has 3 Watts, I am transmitting = 12 Watts of Power)
(If I have a 50 dBm of Signal at my Antenna, and lose -6dB of Gain, I end up with 44dBm)
#3 NUMBER THREE
+10dB = x10, or ten times
then it follows that -10dB is a tenth of the amount.
You can also talk dB's in a purely relative sense, with little Math.
Ex. A VHF transmitter transmits +20 dB of Power, I lose -8 dB in the Coaxial Cable and the Antenna has +10 dB of Gain
What is the resulting Radiated RF Power in dB?
dB = (+20dB) + (-8dB) + (+10dB) = +22 dB
Math in dB's is simple, you just add and subtract, so how much is 22 dB in Watts?
Only if you are given the actual values of what is being measured, can you know the value.
Let's look at the above.... and below...
Lets assume that the reference power is 1 Watt of RF Power;
22dB = 10 log (Watts/1)
10(22/10) x 1 = Watts
158.48 Watts = 102.2
So +22dB referenced to 1 Watt, is 158.48 Watts, radiating from the Antenna, into free space..
So... how many Watts is 20 dB = 10 log (Watts/I) when referenced to 1 Watt?
20 dB = 10 log (Transmitter Watts/1)
(divide both sides of the equation by 10)
20/10 = log (Transmitter Watts/I)
Then take the "anti-log" of the "log" function to eliminate it
then raise the left hand side as Ten to the power of the division that equals 2.0
10(2) = Transmitter Power = 100 Watts
Looking at this from the practical sense.
Some RF Engineers just memorize some of the typical dBw values so that just by looking at the value
They know the Watts.
If we all just worked in Watts, it would be so cool, dBm is not as intuitive as Watts
Just like Celsius is not as intuitive as Fahrenheit, its all about perspective.
And perspectives can be changed, you cannot change that weird Cousin, unless you change your perspective on Him.
But without the dB, our lives would be far more computationally tedious, dB makes things visually attainable
though the power of Logarithms.
An example of an RF Radio Transmitter in pure dB's:
A 100 Watt Transmitter connects to a +10dB Antenna through an -8 dB lossy coaxial cable
a Typical scenario at a frequency of 1.2 GHz
dB = 20 dB + 10 dB - 8 dB = 22dB!!! easy as shit...
Almost close to Flunking 1st Grade.... or being sent back to Kindergarten.
You see how you knew that a 100 Watt Transmitter was 20 dB?
Now if I ask you out of the blue, how many Watts can I radiate given a +6dB Antenna?
Your "membrane" will recall that 6dB is 4x (four times)
@ +6dB Gain...
2 Watts = 8 Watts Radiated (ERP is Effective Radiated Power)
63.87 Watts = 255.48 Watts ERP
100 Watts = 400 Watts ERP
278 Watts = 1,112.00 Watts ERP
1000 Watts = 4000 Watts ERP
+6 dB is 4x the Power...... simple, easy, no real Math other than multiplication.
Do you need to be a genius to do RF Engineering, NO!!!!
You just need to get off that Sofa and open a book and read.
Note: RF and Antennas Gains often come in 2 dB values.
dBi and dBd on Spec Sheets... another freaky thing to worry about.
But when you are aware, and have made a few mistakes, you will catch on.
Like getting slapped on the head by that nasty bully each time He walks by.
Until one day, you will Google, how to get back at a Head Slapping Bully.......
Then He will learn a lesson on messing with the Mind, not just the Body.
The formula for this is dBi = 2.15 + dBd
dBi = 2.15 + dBd
This means that a regular Dipole Antenna (reference) is 2.15 dB less than an Isotropic Radiator
that is an ideal point in space that radiates in all directions equally.
This means that a Dipole is not an Isotropic Radiator, it sends RF power unequally in space.
It radiates with 2.15 dB less than the ideal in all directions.
Photoshop, is the way that people look like an Isotropic Radiator in a Magazine
When they are just Dipoles being manipulated to look perfect, and that does not exist.
Where i stand Isotropic and d stands for Dipole.
Antenna Datasheets have dBd and dBi and you must be careful...
use the right one in your Radio Coverage Software!
I digress, as this is RF Antenna Engineering, not Audio.
But you can see the applications of the Decibels abound
From your iPhone to your Tinder Hookup
From your Tweet to that Facebook post
You owe yourself the knowledge of how it works, else smarter people will play you like a Violin.
Street Smarts are critical, but Technology Smarts are also important.
The Decibel extends outward, beyond Audio Amplification, into Radio and also Sound (Acoustics).
You just read through some very cool shit, now I am taking you out of RF and into Audio on your
Decibel Adventures... to be continued
So how does Sound, Live Music, and dB's work out, what is this all about?
So we can view dB in a relative sense, or when we know the reference
we can calculate the actual Power or Voltages involved.
Curiously marketing companies depend on that the customer, does not know what I am about to tell.
Audio Amplifiers, must be 10x more powerful for You to be able to hear a noticeable difference in Volume.
When you spend money on a 1000 Watt Car Amp, you are really only using 20% of that Power,
The rest of it stays in your Ego and Imagination,
This is how Sound works, and how "Marketing of Watts" is deceptive and deceiving
It empties your wallets faster than a Bad Date....
So what does needing +10 dB more, have to do with my Rattling License Plates!!
Yikes.... and Yes it does... you don't need 1000 Watts to Rattle....
So if I have a 100 Watt Audio Amplifier
I am convinced by an Audio Salesman that a 200 Watt Audio Amplifier will make my world Rock better, will it?
Let's do the Math;
dB = 10 log (200/100)
dB = 10 log (2)
dB = +3 dB
Nope, you won't hear a difference, you need +10dB
So Yes you get +3 dB more Power, that is twice, confirmed by the formula
And you just emptied $300 from your Savings to buy 100 Watts more for nothing!
Doubling Audio Power with just a +3dB increase goes from 100W to 200W, sounds like a great improvement?
Dude, you need +10 dB more power to hear a difference... (and feel that extra Bass shake your booty).
How about if I spend an extra $500 to get a 300 Watt Amplifier?
Is that much more than your 100 Watt or 200 Watt Amplifier?
Let's do the Math;
dB = 10 log (300/100)
dB = 10 log (3)
dB = 10 * .4771
dB = +4.71 (100 Watts to 300 Watts.)
dB = 10 log (300/200)
dB = 10 log (1.5)
dB = 10 * .17609
dB = +1.76 (200 Watts to 300 Watts.)
dB = +1.76 dB or +4.71dB more power, is that worth the extra $800, not.
I don't think so Dude, save it for that Engagement Ring....
Will you hear a big difference, probably not.
A 200 Watt Amplifier and a 300 Watt Amplifier sound pretty much the same as a 100W Amplifier
They just have more Power Headroom that can be handy with the fidelity of Audio "Transients".
You still need pretty much 10x the Audio Power to perceive a noticeable difference in Power.
So put another way, you really need 1000 Watt amplifier to have a better explosion than a 100 Watt amplifier.
At 1000 Watts from 100 Watts:
dB = 10 log (1000/100)
dB = 10 log (10)
dB = 10 * 1
dB = 10; you made it!!!
At 1000 Watts from 200 Watts:
dB = 10 log (1000/200)
dB = 10 log (5)
dB = 10 * .6987
dB = 6.98 or 7 dB not quite...
You may hear a slight difference, but not +10dB
Just stay at 200 Watts....
CAR STEREO POWER MADNESS
BUT YOU WANT 1000 WATTS IN YOUR CAR?
IF YOU USED THOSE 1000 WATTS CONTINUOUSLY, YOUR SPEAKER COILS WOULD MELT
IN FACT WITH MOST HIGH POWERED SYSTEMS
THE 1000 WATT AMPLIFIER IS RUNNING BETWEEN 50 & 80 WATTS AT HIGH VOLUME
BUT YOU ARE BARELY ABLE TO SEE THE ROAD DUE TO VIBRATIONS :)
WHEN BLASTING, THE REST OF THE HEADROOM IS JUST FILLING YOUR EGO
KNOWING THAT YOU HAVE 1000 WATTS TO SHOW YOUR FRIENDS
IT MAKES YOU FEEL BETTER, SO THE 1000 WATTS DOES HELP, EMOTIONALLY
You are made to believe in Thousands of Watts, but Audio Power is not Linear
Neither is Climate Change, IT IS NOT LINEAR...
But I won't do that now, Climate Change is a touchy subject, but we can see it, if we open our eyes.
When in fact any Audio Amplifier runs full-out at 20-25% Continuous Power
That Audio Dummy Load, it heats up as it is a Resistor.
Your Speakers are not Resistors, so you cannot power test your amplifier with a Speaker, it would melt the Voice Coil
This a logarithmic thing, the more you want, you need to pay much more, for a difference, much more.
So the next time you enjoy a 10 Watt Tube Amp remember you need a 100 Watt Tube Amp to make a discernible audible difference.
Then you need Power Hungry Speakers to be compatible with your 1000 Watts.
It is just as absurd as raising the Basket if Players are now all 8 ft. tall, you need bigger more powerful speakers.
Like that Ferrari in a 35mph Speed Trap Town....
I note that speaker efficiency is cast aside, as this obviously was not discussed here.
What you are paying for when you but a 2000 Watt Car Stereo is probably just 100 Watts of Music Energy, and 1900 Watts of EGO.
If you ever could run the system at 2000 Watts, you would need Speaker Voice Coils the size of a Garbage Can.
You my friends, are victims of the More Watts Marketing that has been around for Decades.
You lay out Cash, and then use 10-20% of what you purchased on a good day at the Park.
Do you see the Marketing Watts and Power Hype Fog start to lift?
The reality of Audio Amplifiers, all you really need to Rock out is 100 Watts.
More than that, you have to get a Class D 1000 Watt amplifier, cheaper than Class A/B.
Audio amplifiers use the HEADROOM to not distort when cranked up.
So the reality here, that extra power you pay for is really a guarantee that when you crank up the Volume
You will not distort until you go deaf.
This is how our ears work with relation to Sound, and Sound Power, SPL = Sound Pressure Level.
Also dB, is a dimensionless unit, unless you know the reference and above are the typical types of things the dB is used for.
So, you can in fact work with dB and have no clue what the F it is about (Power, Voltage, Radio, Sound)
You must be informed after or before the fact what it was about, else this is exactly how teachers teach Math
they don't often give real fu!@#ing examples of why you take the Sine or Cosine of an Angle??
What is Tangent? How do I use it in my Career?
Cos, Sin, Tan & Friends...
Sadly, some Math teachers don't really apply the Math, they just teach it.
Until a Court Case asks them, to Calculate the Force of Impact on a Pedestrian hit by a Car
that my friends is applied Math.. not Partial Differential Equations, but that's what they call them
ALL MATH IS APPLIED MATH
$1 Dollar in account + $1200 Dollars deposit = $1201 Dollars Balance; you just deposited $1200 in your Bank Account
You applied Math.... (cool stuff Man).
Just one look above and You may see something familiar if you are into Electronics, the Functions of the Waves....
Trigonometry is awesome, but most Math teachers suck at teaching it!
Now, if they would take an Oscilloscope and a Signal Generator to class
and show you how to determine the Frequency of the Waveform below wouldn't that be cool!
THE OSCILLOSCOPE - THE MOST USEFUL AUDIO TOOL, AFTER THE VOLTMETER (VOM)
THE OCILLOSCOPE ALLOWS YOU TO SEE INSIDE OF THE PATIENT (YOUR AMPLIFIER)
IT'S LIKE THE MRI OF TUBE AMPS, YOU CAN LOOK AT THE MUSIC, NOT JUST THE POWER
SUPPLY VOLTAGES WITH YOUR METER (BUT JUST AS IMPORTANT)
Below I took this picture of my Oscilloscope of a Sine Wave, so how do I know the frequency?
Just by looking at this picture I can determine the frequency?
Yes you can, I will show you how...
Notice that we see what is called a Sine Wave (Sinusoidal for M.I.T. and Georgia Tech Graduates)
OSCILLOSCOPE TRACE OF A SINE WAVE
Each TIME division on the X axis is 0.200 ms (or 0.002 Seconds) from the display T = 0.2ms
The Vertical Y Scale is 0.1 Volts per division so by inspection, that Sine Wave is 0.5 Volts Peak to Peak.
Amplitude is easy, you just count the vertical divisions from the Sine Wave Max and Min...
You can see that it crosses 4 complete horizontal lines, plus 1/2 of a top and 1/2 bottom, that is 4 + 0.5 + 0.5 = 5 divisions
The value of each division, from the display, is 0.1v, hence 0.1v x 5 = 0.5 Volts (peak-to-peak).
The RMS (Root Mean Square) value of that Sine Wave is .7071 of the Peak to Peak
So that Sine Wave is RMS = 0.5 x .7071 = 0.3535 Volts AC RMS
If you apply Ohms Law you need to convert AC Peak to Peak to RMS, so that the calculation works.
If I was to measure this across a 100 Ohm Resistor, the Power dissipated would be P = V (RMS)2/R
P = 0.35352/100 = 0.00125 Watts = 1.25 Milliwatts so a 1/8 Watt resistor would not work, you need a 1/4 Watter.
You can see how much information that simple Oscilloscope Picture offers the "knowing Tube Amp lover"
You can do it, I know you can as you have read down to this point.
I am here to help, just shoot me an e-mail, I love to clone my type, and you will
be a much better Tube Amp owner and loving restorer once you get
my same Infection, this is not COVID 19, this is "TUBUS MAXIMUS 22"
HOW ABOUT THE FREAKIN FREQUENCY...
YOU ARE ON A TANGENT DUDE!
For the Frequency of the Waveform you look at the 0.2 ms, that is a measure of time
You need to convert that milliseconds of time into seconds of time by moving the decimal point
When you do formulas everything has to be in the same units.
In the Metric System we use MKS - Meters, Kilograms and Seconds.
In electricity it is VOLTS, AMPERES, OHMS, FARADS, HENRY'S and WATTS
As long as you place every number in the same unit base, you are awesomely getting ahead!
So to go from milliseconds to seconds, just move the decimal point 3 positions to the left
You then convert to 0.2ms to 0.0002 Seconds, roll the decimal 3 positions to the left
1,2 and 3 to the left, so easy dude, too easy.
Remember that when we take a small number such as 0.2ms and want to convert that to Seconds
Seconds is a much larger unit than milliseconds, so the number in seconds
will be a small one....
0.2ms = 0.0002 seconds..... the decimal went to the Left.
If you took 0.0002 Seconds to Milliseconds, that decimal point would move three positions to the right..
0.0002 seconds = 0.2 ms
How about Microseconds, that is an extra 3 positions of the decimal point to the right..
0.0002 seconds = 0.2 ms = 200 nanoseconds and so on...., another three positions to the right are picoseconds
200 nanoseconds = 200,000 picoseconds
Engineering notation is always about moving the decimal point 3 positions left or right, easy as pie.
0.2 milliseconds is 0.0002 Seconds, as a millisecond is 1/1000 of a second, a smaller amount of time
The blink of a Human Eye takes 1/3 second or 333 Milliseconds, or on the Oscilloscope a Sine Wave of that Period
would have a frequency of:
f = 1/T = 1/.333s = 3 Hz
That is a low frequency indeed, much lower than the 20 Hz...
Now, from start to finish, in the Oscilloscope picture, the Sine Wave Time on the X Axis starts and stops in 1 cycle
You can see this across 5 vertical divisions
We are not interested in the Y axis as than is Amplitude (we already went there), but we use the Y axis lines to measure across the X axis.
So the equation for frequency is;
Frequency = 1/(Time or Period of Time) or f=1/Time, f=1/t
I have 5 vertical divisions of 0.200 Milliseconds, this is 5 x .0002 Seconds = 0.001 Seconds
So the Frequency of that Sine Wave is:
frequency = (1/0.001) = 1000 Hertz = 1000 Hz
You just learned how to, by just looking at a Scope Display determine;
#1: The Amplitude of the Sine Wave by inspection only
#2: The Peak to Peak Voltage of the Sine Wave by inspection and some Math
#3: Frequency of the Sine Wave by inspection and also Math
#4: The RMS AC Voltage Value of the Sine Wave by Googling RMS for the conversion constant .7071
Are you still scared of looking at an Oscilloscope trace, Nah, you got it now!
POWER TESTING YOUR TUBE AMPLIFIER
Oscilloscope, Audio Signal Generator, Audio Dummy Load & AC RMS Voltmeter
Adapters, Cables, Calculator, Pencil & Paper
How many Watts? do you really want to know.
The question everyone asks You when you tell them You own an Amplifier, how many Watts?
The cool part, is that when you connect your Tube Amp to a Audio Dummy Load and use the Oscilloscope
to look at the Sine Wave produced, when you connect your iPhone Signal Generator app to the Amp input.
The answer to this question becomes visible and measurable.
Sine Wave Amplifier Power Testing, allows you to determine and see how many Watts your amplifier can produce.
You have just created an Amplifier Lie Detector!
You crank up the Volume, until that Sine Wave display Distorts
then back off the Volume (Signal Level) until it looks clean again.
With your True RMS Digital Voltmeter now measure the AC RMS Voltage of that clean Sine Wave
As your Tube Amp is heating up the 100 Watt Audio Dummy load you purchased from "Parts Express"
Friends, that is how you power test your Tube (or Solid State) amp. Quickly, no hassles.
You run the Amp(s) into an Audio Dummy Load(s) and bridge that connection into your Oscilloscope while your AC RMS Digital Meter
brides the + and -, provides you the AC RMS Voltage your Amp develops across that 8 Ohm Power Resistor on your AC Voltmeter Display
JUST "KRANK" IT UP TO MAX CLEAN SINE WAVE
JUST UNTIL THE WAVE STOPS LOOKING CLEAN
NO DIRT, IT NEEDS TO LOOK LIKE THE TRACE
ON THE OSCILLOSCOPE ABOVE......
NICE AND SQUEAKY CLEAN
THIS A VISUAL THING, VERY COOL, NO MATH!
HOW TO DO OHMS LAW, THE RIGHT WAY
Once you wrote down the AC RMS Voltage use Ohms Law, to calculate the Watts of Power.
Power = Watts = V2/R
If your meter read 12.4 Volts AC RMS @ 1000 Hz
Power = Watts = (12.4)2/ 8 Ohms (Dummy Load Resistance)
Power = Watts = 19.22 Watts
Rounding up you have a 20 Watt Tube Amplifier at 1000 Hz
Now, you repeat the same measurement at 20Hz, 100Hz, 500Hz, 5000Hz, 10000Hz, 15000Hz, 18000Hz
Repeat each measurement and You have just Power and Frequency tested your Tube Amp.
If you have a Stereo Amp you will need a separate Audio Dummy Load for each Channel.
On your Dual-Trace Oscilloscope you can view both Channels Simultaneously.
This is also a great way to look for Channel to Channel Power Balance (or lack of).
You will likely get less Power when you go down to 100 Hz & greater Powers above 1,000 Hz
What you will find is a POWER CURVE if you take enough data points to plot the results in MS EXCEL.
each extreme will roll off in Power, that is perfectly normal for a Classic Tube Amplifier
REMEMBER TO KEEP THE SINE WAVE CLEAN ON YOUR OSCILLOSCOPE DISPLAY
NO SUCIO, NO DIRTY SINES, NO CHEATING, NO CLIPPING
SO DOES MATH RULE OR WHAT!
Hey Sine, Cosine.... Log, Pi, get the picture? Trigonometry? Music? Amplifiers?
If you know Trig it helps to understand Amplifier Power and much more about the world
You would not have been getting Stoned before Trig Class!
We need more "Patch Adams" Math teachers, and less of what Roger Waters sang about on
We need Teachers that make Us laugh at the Formulas, not hate them.
ABOUT SOUND POWER - SOUND PRESSURE LEVELS (SPL)
Sound as in a Concert, at Home or a Political Rally Megaphone is dB-SPL
Sound is expressed in SPL (Sound Pressure Level) as in dB-SPL
the denominator (reference) is 0.00002 Pascal
V2 = 0.00002 Pa (Pascal) a unit of Pressure.
So when you are told that Hearing Damage happens at high SPL, you may not have known that
Deep Purple was the highest measured Rock Concert in History +117 dB !!!!!
In 1972, Deep Purple was recognized by the Guiness Book of World Records
as the "globe's loudest band" for a concert at the London Rainbow Theater
during which three members of the audience fell unconscious.
+117 dB Deep Purple SPL, how much sound pressure is that, and how far from Stage?
Well the SPL is based on the distance form the Sound Source
Sound decay's over distance, the farther from the Band, the lower the SPL
a simple dB SPL formula does not take into account distance.
So I have to guestimate this from the +117 dB.
Let's assume that the measurement was not taken on-stage (most likely)
but at some distance away from the Stage to make 3 people pass out.
I opened an online SPL Calculator and ran some numbers on this Concert and this is what I got;
Let's say that someone measured +117 dB SPL standing 40 feet from the stage
This sounds reasonable for a good spot up front close to Blackmore, Glover, Paice, Lord & Gillan
At 40 feet, and +117dB, the Band must have been playing near 133 dB SPL!!!
How these guys survived, is amazing, they certainly had Hearing protection.
Ted Nugent almost went deaf on Stage
Ted knows the Hazards of being a Rock Star on-stage with no hearing protection.
+117dB is an "insane" level of Sound Pressure Power @ 40 feet from Stage.
Sound is measured in decibels (dB).
A whisper is about +30 dB
Normal conversation is about +60 dB
Motorcycle engine running is about +95 dB
Noise above +70 dB over a prolonged period of time, may start to damage your hearing.
Loud noise above +120 dB CAN CAUSE IMMEDIATE HARM TO YOUR HEARING
SounSound pressure level (SPL) is the pressure level of a sound, measured in decibels (dB)
Sound is equal to 20 x the Log10 of the ratio of the Root Mean Square (RMS) of sound pressure.
the reference sound pressure in air is 2 x 10-5 N/m2, or 0.00002 Pascal
This is the reference value in the denominator of your SPL = 20 log (Pressure/0.00002)
Recognize the Formula? same one, but a different application, Audio Sound Pressure!
So people, when you Crank up your Audio System, try to keep the SPL below 85dB MAXIMUM
Keep your distance from the Speakers..... if the system is loud.
Buy a Sound Level Meter, cheap insurance I have one and it works great to save what is left of my Hearing
Measure the average SPL from your Sofa, and adjust volume to suit You (and keep the Wife happy)
I lost hearing at Van Halen in 1991, Roanoke VA.
My ears rang for 4 days, after the show, and all the way Home from the Show
I was 50 feet from the stage, and had to get away after the 4th song was over
My wife and I leaned across the rear wall, it was LOUD
During Alex's Drum Solo, a panel of the Central Scoreboard came off and
fell down, cutting a Lady who was rushed to the ER by Security
Covered by a bloody White Towel!
If you were at that concert, you were lucky.
Not to be under the Scoreboard that was more than 60-70 ft. above the arena
Not even RAMMSTEIN at the Globen in Stockholm was as loud
And Hearing Protection was being provided for FREE at that Show
You got to Love the Swedes, they have a Wonderful City and Great People
I just wish that the new entrants, would respect that, and not behave so entitled
St. Maarten decibels & thrills
Radio Signals like Sound attenuate over Distance
This is why you need Hearing protection when close to a 747 Plane
Believe me, I was there in St. Maarten having a Beer near the Runway
and it is LOUD. These people below are nuts!
Those Engines can kick up rocks and take out your Eye!
They hang on to the Fence and challenge Darwin, not I.
Now how about Current?
Currents are not usually expressed in decibels..... just a fact of the matter, I will do some research as to why?
Also just as well it is unusual to find electrical specs in terms of AC or DC Currents and it has always bugged the F. out of me as an Electrical Engineer
I always shout: GIVE ME THE FKIN CURRENT DRAW! DAMMIT!
JUST ASSUME A POWER FACTOR OF 0.9 IF AC, MAKE A DAM ASSUMPTION!
Without knowing the Current loads, it is more difficult to do a solid Power Load Analysis!!!
And if they just give me the load in Watts, if it is DC great, but in AC I need the Power Factor!!!!
When you see a decibel, it must have some basis....
else you will not be able to do Apples to Apples comparisons...
If you just get dB's you are forced to exist in the world of Addition and Subtraction of dB's and
that is cool sometimes, and very un-cool in other situations.
The beauty of the decibel is that they add and subtract as whole numbers....
The reality of Engineering, we also have our Pet Peeves.
Commonly used Decibel notations
dBm (referenced to 1 milliwatt)
dBw (referenced to 1 watt)
dBuW (referenced to 1 microwatt)
dBv (referenced to 1 volt)
dBmV (referenced to 1 millivolt)
dBuV (referenced to 1 microvolt)
there are more, just Google them....
You must learn Ohms Law, end of story
No Ohm's Law, No practical Amplifier Repair verification
No Joy without measurements!
Working "blind" is not a good place to be
Faith is for religious folks
Science relies on hard data
Politics relies on backstabbing
Herr Georg Ohm
VOLTAGE = V
CURRENT = I
RESISTANCE = is futile :)
WATTS = POWER = P
Voltage in Volts = Current x Resistance is Linear
V = I x R
I = V/R
R = V/I
Power in Watts is Linear and also Exponential
Watts = P = V x I
Watts = P = I2 x R
Watts = P = V2/R
Hello again, its your Membrane...
Memorize these formulas, you will not regret them one bit
The troubleshooters "Secret Sauce"
Like they were your Girlfriends/Boyfriends/Partner/Dealer's new Cell Phone #
The great thing about Electrical Circuits, they all follow Laws...
Kirchhoff's Law, Norton's Law, even Harvard Law.....
Unlike some, who may eventually do something stupid and....
Congratulations if you have made it this far..., You are on the path towards Tube Valhalla
The righteousness of the Electron Tube, Music in a Vacuum, just like Astronauts in Space
The electron jumps from the Cathode to the Plate
The Astronaut jumps from the Earth to the Moon.
Both travel in a Vacuum.
Dude, that was sooo deep!
Not currently broadcast on Mainstream Media, or Streamed on YouTUBE
This is the place that you have been working towards
Tube Valhalla.... enjoy my Web Pages, you just graduated
"Summa Cum Valvo"
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