Actually, I may have been thinking of Pa which is power dissipation at the plate (anode). And Pd is power dissipation at a point not necessarily known by just Pd, therefore it could be dissipation at the anode, grid, or cathode (k). This is still so new to me, that things are yet running together. Hopefully, things will become clearer soon. Someone mentioned being able to read 'charts' on the datasheet to figure things out. I have looked at them on occasion but they don't make a lot of sense yet.
A different but related subject is the winding of transformers. A mystery that is not easily attached by knowing the ratio of the number of windings in the primary and secondary, would give the ratio of voltage on each side. Not nearly enough info. The next thing is 42 divided by the cross-sectional area of the iron plates in sq cm gives the turns per volt. This, apparently, is still not enough info. Somewhere among these things is the need wire gauge, but that is determined by the ampacity one is needing. From there, one needs to be an electrical engineer to finish making calculations. If only the 1st three things were necessary, I'd be golden. These are things, I'd like to do at least once, just to say I did it, and made it work. I saw a few people on YouTube making their own tubes. I considered that for a minute and decided that doing that is not for me. The YouTuber said his tubes only make a half watt. That may be ok for a bedroom practice amp but not for a 100 watt head. TY
BTW, the Wa curve in the Philips graph shows the PD for 2 tubes.
It gives 41W at 100W output confirming my "math" above.
It gives 41W at 100W output confirming my "math" above.
Well, I have a background in physics, thermodynamics and control systems.
So I just look from a much bigger picture.
So therefor the equations I showed at the previous page, count for ANY kind of system.
(might as well be a mechanical system)
Any system (incl amplifiers) just have certain input power and power that is being used useful.
The rest is just waste, most of the time resulting in heat.
So yes, the practical side is a bit more nuanced, although in a tube the most of the bulk (current) is going through the plate.
But you're correct that a part heats up the cathode as well.
Although I have never seen a cathode power dissipation.
Assuming that the anode power dissipation is far bigger than the cathode power dissipation.
Anyway, for the system efficiency and total power waste it doesn't matter.
There is for example also a bit wasted in the screen grid, but that is much lower compared to the anode.
I went back and checked the datasheet. You are correct, no cathode dissipation. For the example I viewed, there was a mA rating of 20mA. There was no voltage rating listed, so therefore no cathode dissipation or at least not one that was applicable.
This discutions are useless about this matter , you have a power supply wattmeter , a load wattmeter and you calculate the efficiency. Simple .
Assume. Are you familiar with what happens when one assumes? I have none of these tools. Further, I am not asking about any amps that I have built. I am trying to learn what various tubes are able to produce in terms of output power for potential builds. The 6AQ5 and 6BQ5 both have Pd of 12 watts, I believe. However, the 6BQ5 can produce greater output power. So between the two, I would rather use the 6BQ5 if I were only seeking a higher output power.
Ok , I hope you understood that in class A single ended , the output power is always lower than 50% tube dissipation
For push-pull the output power is higher than one tube dissipation , how much depends on design efficiency . Can be lower in some situations , if you want to be inefficient , as we don't use tubes for efficiency but sound quality.
For push-pull the output power is higher than one tube dissipation , how much depends on design efficiency . Can be lower in some situations , if you want to be inefficient , as we don't use tubes for efficiency but sound quality.
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Meanwhile it should be clear that it's not possible to predict output power from just looking at PDmax.
Instead get acquainted with a good online loadline calculator, like this: https://www.vtadiy.com/loadline-calculators/power-stage-calculator/ and play with the settings, while observing tube voltage and dissipation limits.
That was my experience 25y ago as well. These start to glow >25-28W.
Didn't like the sound either. In my amp at the time they didn't sound bad, just boring.
You can use them in a power supply?
6BQ5= 4.8 watt heater, 6AQ5= 2.8 watt heater. More heater is capable of pushing more current so you can get more power.
Never noticed the diff. in heater currents with the 6AQ5 and the 6BQ5. I wouldn't have known what the difference meant. Somewhere I wrote that something like only AC could go through a capacitor and transformer winding. I realized that was only half true. DC can go through transformer primary windings but won't induce any current in the secondary windings. Actually, that may not be totally accurate either, but at the very least the DC current would have to be changing to induce a current in the secondaries.
This is not true , heater can be more efficient in some tubes
The voltage rating is a bit lower for 6AQ5 , 275V vs 300V
In datasheet with 250V B+ , output power is 10W for 6AQ5 and 11W for 6BQ5 , so very similar , the difference is because the first needs 10K Raa and the second only 8K
Of course the little 7pin base tube would have a shorter life at max ratings
Depanatoru,
Thanks for the data sheet (earlier I thanked 45 for the graph).
45,
On that data sheet, generally I see 10% distortion for single ended.
And on that data sheet, generally I see 5% and 6% for push pull.
The exceptions of some operating conditions are 3% and 8% distortion.
In no case do I see 2%, and certainly not 1% distortion, clearly some kind of distortion is needed.
Rikaro,
I probably did misread the current on the graph.
I am reminded of the Dyna ST-70 that I owned. With the bias properly adjusted . . .
More than once I remember seeing Red Plate EL34 tubes.
"All tubes are equal, but some tubes are more equal than others"
Caveat Emptor
Many Transmitter tubes were made to operate with Red Plates
EL34 tubes were not made to operate that way.
Everyone,
The idea of having two 100 Watt mono-block tube amplifiers in my house gives my Hernia Surgeon something to do.
If I listen at levels of 200 milliWatts to 6 Watts, what is the point of a 100 Watt output?
Re-Liable amplifiers, or . . .
Liable to have another Hernia surgery?
Do you need better efficiency?
Change from Tubes / Valves threads to Class D threads.
Or, design your own vacuum tube class D amplifier.
Thanks for the data sheet (earlier I thanked 45 for the graph).
45,
On that data sheet, generally I see 10% distortion for single ended.
And on that data sheet, generally I see 5% and 6% for push pull.
The exceptions of some operating conditions are 3% and 8% distortion.
In no case do I see 2%, and certainly not 1% distortion, clearly some kind of distortion is needed.
Rikaro,
I probably did misread the current on the graph.
I am reminded of the Dyna ST-70 that I owned. With the bias properly adjusted . . .
More than once I remember seeing Red Plate EL34 tubes.
"All tubes are equal, but some tubes are more equal than others"
Caveat Emptor
Many Transmitter tubes were made to operate with Red Plates
EL34 tubes were not made to operate that way.
Everyone,
The idea of having two 100 Watt mono-block tube amplifiers in my house gives my Hernia Surgeon something to do.
If I listen at levels of 200 milliWatts to 6 Watts, what is the point of a 100 Watt output?
Re-Liable amplifiers, or . . .
Liable to have another Hernia surgery?
Do you need better efficiency?
Change from Tubes / Valves threads to Class D threads.
Or, design your own vacuum tube class D amplifier.
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If I listened at 6 watts of average power I’d want MORE than a 100 watt amp. It would be clipping and damn loud, especially with my 99dB/W “tube” speakers. My 200 watt mono blocks are in a rack on WHEELS.
And no, I don’t use that system all the time. When I’m in the mood for a Who concert while working on the shop there is no substitute.
And no, I don’t use that system all the time. When I’m in the mood for a Who concert while working on the shop there is no substitute.
I wonder how practical that actually would be. You’d need tubes designed for switching - probably horizontal deflection tubes, and dampers for the freewheeling diodes. Then getting enough drive to make square waves at 200+ kHZ - probably transformer coupled. I’ll bet the output filter inductor is going to be a real S.O.B. to design/build, too.
You know nothing about cathode feedback. That is clear!
I said that your estimate of THD reduction is NOT VALID for cathode feedback. Distortion can be 5% and with 7 dB cathode fbk it goes down to 1-1.5%.
Actually the original Schade article with the 6L6 PP shows that 10% local fbk results in about 6.5 dB for the amplifier taken into consideration and reduces distortion from 2% to 0.6%. So 6.5 dB of local fbk reduces distortion by 10.5 dB.
Moreover the 32W 6L6 amplifier does 2% without any feedback!
Please stop your argument. You have no clue on this.
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45,
I am not arguing.
I have used cathode feedback.
Yes, I was surprised at how much the distortion went down; and at how much the frequency response improved.
And I did not say that cathode feedback does not work, and work effectively.
My distortion statements were for NO negative feedback (before applying any form of negative feedback).
I also said about the 5% distortion listed on the tube data: "
Obviously, two things are needed:
1. Negative feedback to get the distortion down to 1%"
do not worry about the other thing, negative feedback is paramount here, no matter what the NFB method is.
A general statement that 6dB of negative feedback reduces the distortion to about 1/2 of what it was before the negative feedback was applied . . .
is exactly that, a general statement, and 'about' 1/2.
I guess I have to re-read all my posts, my 78 year old memory is faulty.
In that case . . . I apologize.
I am not arguing.
I have used cathode feedback.
Yes, I was surprised at how much the distortion went down; and at how much the frequency response improved.
And I did not say that cathode feedback does not work, and work effectively.
My distortion statements were for NO negative feedback (before applying any form of negative feedback).
I also said about the 5% distortion listed on the tube data: "
Obviously, two things are needed:
1. Negative feedback to get the distortion down to 1%"
do not worry about the other thing, negative feedback is paramount here, no matter what the NFB method is.
A general statement that 6dB of negative feedback reduces the distortion to about 1/2 of what it was before the negative feedback was applied . . .
is exactly that, a general statement, and 'about' 1/2.
I guess I have to re-read all my posts, my 78 year old memory is faulty.
In that case . . . I apologize.
wg_ski,
When I am listening to my tube amplifiers at 2 feet away, the power is often about 200mW on the peaks.
When I listen to my tube amplifiers in the living room, the power often reaches 4 Watts peak or 6 Watts peak.
100 Watts peak on my speakers, and with my ear doctors recommendation about loud noises, etc.
No Way!
Class D vacuum tube amplifiers?
I thought that practicality is in the eye of the beholder.
I had the idea that some of the Berning amplifiers were efficient, guess not.
I guess its claim to fame (if there was fame) was about something other than efficiency.
When I am listening to my tube amplifiers at 2 feet away, the power is often about 200mW on the peaks.
When I listen to my tube amplifiers in the living room, the power often reaches 4 Watts peak or 6 Watts peak.
100 Watts peak on my speakers, and with my ear doctors recommendation about loud noises, etc.
No Way!
Class D vacuum tube amplifiers?
I thought that practicality is in the eye of the beholder.
I had the idea that some of the Berning amplifiers were efficient, guess not.
I guess its claim to fame (if there was fame) was about something other than efficiency.
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Black 1927 is only an approximation, so it actually is possible to reduce THD by more (or less!) than reduction of gain in low feedback situations. The penalty is some redistribution of harmonic components from lower to higher. At much higher levels of feedback this effect decreases and everything approaches Black 1927.
All good fortune,
Chris
All good fortune,
Chris
There is no high harmonic content either. It is dominant 3rd harmonic, very little 5th and 2nd + 4th to follow. Maybe high harmonics show at higher output level but honestly the harmonic content of 1% THD at 100W output has very little importance even if I used 80 dB/1W/1m speakers. None will ever able to hear anything not only at 1m but also at 2-3 m with the stereo speakers singing.
What is most relevant is that the pentode amp + cathode feedback sounds like as zero fbk triode amp. This does not happen with pentode + same amount of GRND fbk. Even worse if GRND fbk is increased......
What is most relevant is that the pentode amp + cathode feedback sounds like as zero fbk triode amp. This does not happen with pentode + same amount of GRND fbk. Even worse if GRND fbk is increased......