# What Plate Dissipation is - something doesn't seem right

Discussion in 'Amp Tech Center' started by peteb, Jul 28, 2017.

1. ### petebFriend of Leo's

Apr 25, 2003
Plate dissipation doesn't seem to be clearly defined and I think there are some misunderstandings. I know it doesn't all make sense to me.

It's accepted that tubes have a maximum plate dissipation.

This is a standard spec for the tube type, and how it gets used is people set their idle bias plate dissipation power to some percentage of this, or right at it, cathode bias, or even over it, class A cathode bias.

It is also said that plate dissipation is the wasted energy leaving the tube as heat.

These can't all be true it can't all be the same thing, this is my comment.

The RCA tube receiving manual says that plate dissipation is the difference between the input and output powers of the tube. They might also say heat, I can't remember.

I think everything above this point is universally accepted, except for my comment.

This is what I think does not seem right:

If you measure the plate dissipation of champ at 15 watts, what does this number mean about the operation of the amp? Is it a measure of the heat leaving the plate as wasted energy?

What power is input to the tube? What is the output power of the tube? What is the wasted heat energy leaving the tube?

Which of the three is idle bias power?

The idle bias power is DC, and the output power is AC put on the OT by the tube, so it's not the output power.

The idle bias power is the high voltage DC applied across the tube multiplied by the current flowing thru the tube, huh. What is the power input to the tube? Wouldn't it be the voltage applied across the tube, and the current fed thru the tube by the power supply, multiplied togethor?

Why does the idle bias power seem so much like the input power? And what happened to the heat?

The biggest number of all of three would be the input power. It has to be.

If the wasted heat is 15 watts, then how big is the input power? It has to be bigger than 15 watts, but how do you measure it? Not the power input into the amp, but the power input to the tube.

This is the only way I can make any sense of it:

The idle plate dissipation that we all are familiar with is actually the input power. The idle plate dissipation in the RCA receiving tube manual, actually is The wasted heat, which would be very hard to measure. The input power is the full output power of the tube plus the energy wasted to heat. This conveniently explains what is going on in a champ biased at 100+ percent.

The power out is the full 12 watts, the power input is 15 W, making the heat released as 3 W.

Or maybe it's 11 + 4 = 15?

So when you measure the idle bias plate dissipation, you are measuring all the power going into the tube including how much energy is wasted as heat - this is the connection.

This is the most important number as far as how much abuse the tube is receiving.

That is the most I can make out of it.

I would really like to hear what other people think

Thanks

Last edited: Jul 28, 2017

Mar 26, 2014
Northern Germany
What I make of it.....

Think of a room 36 foot high, but just the right size to fit a trampoline in.
Put a trampoline in it on the floor - no bounce
Put the trampoline up, 8 foot away from the ceiling - bounce once and break your neck.
Put the trampoline exactly in the middle of the room - what about your body height ?
Put the trampoline in so that your head is in the middle of the room - the bounce not bad, but you never go down as far as you can bounce up, lots of wasted room underneath.

The maker of the trampoline says "Maximum bouncing person weight and drop inertia to room height /floor clearance ratio 100% = XXX"
Then you can play with these variables, depending on weight used, drop force, height setting and room height. ( Rooms with a pit under the trampoline are Class AB (added bounce))

You can of course change the trampoline, a 6V trampoline has different tension springs and jumping surface strength than the EL3 trampoline, and is suitable for different rooms.

So setting the best position for the trampoline is what we call biasing it. This gets the most bounce out of it, allows for the higest potential power.
These are the makers suggestions, and it is sensible to stick to their advice.

Let us assume that the thing holding the trampoline up gives off heat, and the higher it holds it, the greater the heat it emits.
Of course there is a degree of lost power with every bounce, given off as heat from the trampoline, but mostly from the person bouncing (confined in the same room).
How does the height setting relate to how hot the person bouncing can get get towards Hyperthermia or even Hyperpyrexia and die?

What is the power of the trampoline ?

The height setting (bias) is a potential that effects power, and uses some power, but - Bias is a potential, not a power.

The idea of relating individaully to either, the height jumped, or the pre-bounce inertia, or the weight of the bouncer, - to amount of heat in the room, and then using this as a deciding factor and as the means of setting the height of the trampoline from the floor, whilst at the same time ignoring the tension of the trampoline surface, makes as much sence as this latest excursion into meaningles conjectures that you now seem to be entering.

The tension of the trampoline, related to the size of the bouncy surface is a factor that one could liken to the screengrids of tubes and there voltage setting, just to strech the analogy.

What do I think.... That you should perhaps read more of the extensive literature related to tube technology, rather than write about it.

Last edited: Jul 29, 2017
Phrygian77, telemnemonics and RLee77 like this.

Mar 26, 2014
Northern Germany

So which part of the formular don't you agree with, and how would you like to express it?

But how does theory over distortionless Class A relate to a guitar amplifier ?

Theories over overdrive situations can only be empirically deduced, and are based on the experience and personal preferances of the practitioner. There is no accounting for taste!

Last edited: Jul 29, 2017
SonsOfMoog and RLee77 like this.

4. ### DaciousPoster Extraordinaire

Mar 16, 2003
Godzone

You take an amp say a Deluxe Reverb with everything in spec, apply a continuous input with everything on max. You plug it into a wall socket. Presuming 117volts goes in and the supply is reliable, at the speaker terminals if you measure current and voltage and multiply them in the formula (I x R = P) where I is current, R is voltage and P is power in watts. It'll be 22 + or - 10%. Or not depending on how much Fender is advertising truthfully.

What happens to the idle current consumed by the tubes if there's no input? They just generate heat and warm the surrounding components and atmosphere. Play nothing through the amp and the tubes will last a long time, having done no work. So will the rest of the amp.

Leave an amp operating with no input it'll heat everything up around it. Go back in an hour and feel the chassis, transformers and tubes. That heat is the power being consumed by the power section, idling.

Because the basic circuit was designed in the 60's using 19th century tech, it's very inefficient in power usage. So it chews a lot of power and wastes it as heat.

Now - we know from the tube manufacturers that their product will 'live' at certain voltage and current. So that's - working backwards and forwards - what the power transformer, rectifier circuitry, preamp, output transformer and speaker are soecced around.

You're in business to make money, and for reasons of competition and cost containment your product has to be reliable, good performance, well priced and sellable at a margin that makes you a profit.

Everything on the amp is developed around that. The tubes, what they idle at and power they dissipate is all just a small but important part of that equation.

The voltage that appears at the plate, and the current the power circuit allows, is what the amp maker chose during development. As we know in various designs they went over the vendor's tube spec. And tube life may be shortened as a result. Do we care? Maybe not much. Tubes are pretty cheap. I can cope with replacing them periodically.

Can we do it more efficiently and effectively? Yes. But the fact more 1950s and 1960s spec tube amps are being made now than ever sort of indicates we don't want to.

Last edited: Jul 29, 2017

5. ### petebFriend of Leo's

Apr 25, 2003
Awesome Bendyha! Thank you

It's going to take me a little while to digest, but I want to say I appreciate your input. I will respond.

6. ### petebFriend of Leo's

Apr 25, 2003

Dacious, I think your posts show a lot of insight. I haven't read your post yet, but I am going to read it with interest.

In regards to your comment above, I completely respect your opinion, there is truth in there, but if other ampsters continually roll amps, tubes, speakers, and I don't do any of that, isn't it OK for me to obsess in a different way, get into the inner workings of the amps?

And maybe, you are misunderstanding my focus here too, I want a better understanding of what plate dissipation is, nothing more, seems kinda normal to me?

7. ### DaciousPoster Extraordinaire

Mar 16, 2003
Godzone
Plate dissipation is merely the conversion of electrons creating force into other forms of force. Because it's an electro-chemical reaction, and the reagents resist there's heat involved. In fact, most of the energy released by atoms crashing into the plate is released as heat waves.

Some of the energy that's liberated forms the power, in DC between the plates, which swings backwards and forwards like a bicyclist pushing pedals.

A tiny bit is released as light - the heaters and sometimes plates themselves glowing. If you had someone with a spectrometer and infrared camera they could quantify it.

Or, you could just accept the physical evidence. You can measure the voltage and current consumed from the wall socket, into and out of the power transformer, out of the rectifier, into the plates, into and out of the output transformer. The difference between what goes into the power transformer and what comes out is the losses, nearly all heating up transformer windings. Same with tubes, same with output transformer. If you measure volts and current in to the power socket , and volts and current at the speaker taps you can work out 3/4 or 4/5 of the power is system losses - heat, chemical and thermal reactions, parasitic losses in components.

Last edited: Jul 29, 2017

8. ### dsutton24Poster ExtraordinaireGold Supporter

Dec 29, 2010
Illinois
Plate dissipation is easy to define, it's simply the maximum amount of heat that a plate can safely dissipate, be it wasted heat, useful output, ambient temperature, or some combination thereof.

May 10, 2017
Tucson, AZ

10. ### petebFriend of Leo's

Apr 25, 2003

Thanks Bendyha, I like the trampoline analogy to bias.

11. ### petebFriend of Leo's

Apr 25, 2003

I guess the simple version of what I'm saying is, when you measure the idle bias power plate dissipation, it seems to me that the input power is being measured, not the heat dissipated from the tube as wasted heat energy.

But the wasted heat energy comes from the input energy, so when you measure the input power, you are in a way also measuring the wasted heat energy.

????????????????????

12. ### petebFriend of Leo's

Apr 25, 2003

Thank you Dacious, that is a good description of dissipation.

13. ### petebFriend of Leo's

Apr 25, 2003

Thank you Dsutton, very concise!

14. ### petebFriend of Leo's

Apr 25, 2003

Thank you old tele man for the links, I think ive been thru what these typical sources have on dissipation. I just did a little browsing of what your links have.

Didn't the beginning of my original post say most of what these typical sources say?

What they say on page 78, as you mentioned, in the RCA manual, is exactly what I posted in post 1.

So why am I not satisfied with the standard answers?

#1: when you measure plate dissipation on your amp, it does not look at all to me that the wasted heat is being measured. It looks exactly like measuring input power, and that is a disconnect.

People get put off by my not accepting the standard answers, I am sorry about that, and I can't help it, it's just me.

When I ask these questions, I'm not looking for the standard answers, I can read, I have read, I am looking for insight beyond the standard answers, there are a lot of knowledgable experienced people on this forum that have insight based on experience, that is more than you can read in any books. I'm interested in people sharing their first hand experiences, that's what makes the TDPRI the great place it is.

Mar 26, 2014
Northern Germany
This is more than clear. Largely due to the fact that you seem to fail to understand them, or so it would appear from the follow-up question or statement that you then tend to respond with more than adequately proves.

It is not so much the questions that bother people here. It is your brash statementments of false truths that you constantly spurt forth. Claims that are blatently wrong and misleading. Stateing suppositions that are far from reality. Drawing relatiionships between factors that are unrelated. The missuse of terminology. The repeated claim that you understand thing that you don't.

Then why do you keep making false statements about some of the most basic things at times, things that any decent book would have covered? You ask very basic questions at times that prove little comprehension. You make statements that people with a basic knowledge would not have made..knowing them to be false.

You word questions ambiguously through use of your light technical grasp, shifting the premise of the conversation. Just now you ask..."#1: when you measure plate dissipation on your amp,"......do you mean at idle ?

Then...."there are a lot of knowledgable experienced people on this forum that have insight based on experience, that is more than you can read in any books. I'm interested in people sharing their first hand experiences,..."

So much has been offered you to try to help you understand, so many solutions to the problems you seem to have, ...with nobody agreeing with your false supositions....but you fail to accept this knowledgable wisdom and first hand experience, like someone whipping a healthy horse for not eating blue plastic grass you offer it, so you change it to orange and try again.

None the less, keep asking your nonsense.....and I can keep on telling you that you are writing nonsense

Why...because you are filling this otherwise very reliably informative forum with disinformation and alternative (un)truths.....which I dispise. Everyone is free to express an opinion, which is narurally fine by me, but you sometimes tend to go beond that, and make false, misleading, and at times, irresponsibly dangerous claims.

Last edited: Jul 30, 2017

16. ### Old Tele manFriend of Leo's

May 10, 2017
Tucson, AZ
Again, you are confusing DC-power (idle) and AC-power (output) and their combination (AC on DC) which is what the tube plates see while operating:

"Average value of combined zero- and maximum-signals is approximated as:

X(avg) = (Xq/2 + ∆X/4).

NOTE: ∆ represents AC-change in voltage (VAC) or current (IAC) and q denotes quiescent or idle values (VDC or IDC)."

Remember, POWER is an "average" (..per unit time) value while the applied and output voltages and currents are DC and RMS values.

Last edited: Jul 30, 2017

17. ### dsutton24Poster ExtraordinaireGold Supporter

Dec 29, 2010
Illinois
Insight and accurate, useful information are two very different things. If you took everything that has been posted in this thread so far you have about 30% information that is correct, or at least close enough, and 70% insight. That 70% isn't useful.

The things that you are trying to distill into a few overarching principles won't get you to the broad knowledge you need to amass if you want to understand amplifiers. There are no good short cuts. You need to start with the basics and work forward. Trying to pick a few concepts out of the middle of the process isn't an education. It's just a collection of random ideas, that, depending on who you are listening to at any given moment, may not even be accurate.

Last edited: Jul 30, 2017

18. ### petebFriend of Leo's

Apr 25, 2003
Thank you old tele man, I really think I have that accounted for.

19. ### petebFriend of Leo's

Apr 25, 2003

Thank you dsutton, I appreciate your input.

I think if you read my posts closely, you will realize that I AM taking the wholistic approach!

20. ### petebFriend of Leo's

Apr 25, 2003
The standard rules and guidelines are only a starting point, there is also an ending point, which is rarely the starting point.

Take Leo and the tube specs, he seemed to totally disregard the specs, but I bet he was very familiar with the specs.

A true expert, knows and fully understands the standard rules and guidelines, AND knows when and how to properly apply them.

Most of the info that has been regurgitated, without thought as to how to apply it in different situations, is information that some one becoming interested in the amps could probably come up with and be able to repeat in day 1 of learning amps. I consider it the very basics, the starting point.

IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.