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In Reply to: RE: Maximum Output posted by Tre' on January 27, 2015 at 13:24:53
Obtaining correct Impulse response under changing musical conditions is the electronics that produces the best musical results.
NOTE: The QUALITY of the output trans is a larger factor than its loading-- if loading is already in the Ballpark. Mike and I designed my newest transformers for the 43 ma. load.
Guess what? We decided on 2.5K-- again. We changed a few other things in the transformer formula to get what I want musically. I agree that extra inductance helps "control" woofers. Guess what again-- it's the WRONG way to control woofers! It ALSO slows down the woofer's impulse response, and reduces overall clarity..
I have a proven way to absolutely control woofers-- my design does it to perfection. Build a LSES power supply, and then get an output tube that can be loaded "hard" without distorting music, and then use short, large wiring in the amp to tighten the speaker-to amp's components interface. Sure does work for me!.
I won't discuss whether either of us transformer nuts "doesn't know much about electronics". That depends-- Whose electronics?
Another factor is the 2A3 vacuum tube. If you're running or calculating the NOS RCA-- single-plate or BiPlate-- I don't care-- I've used 'em all-- I do feel for you!
Before you play GOD, why not get some GOOD tubes, and MEASURE the impulse/loading tests on THOSE? I'm thinking EML and JJ-2A3-40, maybe an ELROG some fine day?.
Heck! I could load-up a JJ-2A3-40 at 1.5K, and it would still Kick-Ass as long as the power supply could support it, and distort very little, if run right. No, I'm not that crazy, 2.5K is a terrific compromise with THIS transformer design in THIS amp.
The JJ 2A3 triode-- this isn't Pentode-loading!-- is very tolerant of loading variations, which allows one to "load 'er-up", and get insanely different results than those old tubes (and antiquated published specs) could ever deliver.
What happens if you sock an old 2A3 into one of my amps? Nothing, really. It runs fine at 43 ma. But is it an ideal match for this design? NO. The JJ and the EML are.
The old formulas DO NOT APPLY to modern tubes. Especially the ones from Czech and Germany. SOB!!!!
I want to try some ELROGS! Can anyone talk ELROG into a 2A3 and maybe a 45?
Do I have to step down (musically) to a 300B to get an Elrog?
---Dennis---
Follow Ups:
"The JJ 2A3 triode-- this isn't Pentode-loading!-- is very tolerant of loading variations, which allows one to "load 'er-up", and get insanely different results than those old tubes (and antiquated published specs) could ever deliver."The JJ 2a3-40 data sheet says the plate resistance is 800 ohms, same as an old RCA.
Are you saying that the JJ tube's plate resistance is wildly different than what is stated by JJ on their data sheet, allowing it to be happy into 1500 ohms at 43ma./250 volts when clearly the RCA would not be?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 01/28/15
Nope! I'm not saying that at all.
The JJ simply doesn't go into minute convulsions at 43 ma. if it's "overloaded"-- (distortion!)--- anywhere nearly as much as old-design tubes-- just because the load changed a little bit.
It's FAR more load-tolerant. It's like a CAT D-9 up against a Bobcat.
I think we both can predict the outcome of that.
Sure-- JJ had to "meet" the old specs-- otherwise, people won't buy the tube and plunk it into their creaky old amps, and yes, the advertised plate resistance is 800 ohms. I said ADVERTISED-- and yes, it will measure-out-- it's not wrong. If one uses the old calcs. for a 2A3, and plunks this tube in, it will operate just like the old NOS tube. But, there, the similarities END. .
This is a new, better, and far more versatile tool, so learn to use it-- which is just what I did. When I get a new tool, I find out what IT does--- I already know what the old tool does-- but I'm going to use the new tool, so I study IT as well as the old tool.
These tubes (JJ and EML, etc.) are designed to operate at far greater dissipation levels than old 2A3's. The JJ-2A3-40 will dissipate up to 40 watts, not crap-out at 15.
At 250 volts across it, and at 43 ma. plate current, one might expect that it would be rugged alright, (it is), but it might not cater well to the low plate current. NOT SO! It sounds clean, clear, fast, ultra-dynamic, super-powerful and has a super-wide bandwidth.
Into 2.5K? That's coasting on a Banana Peel for it. This thing could drive 1K! No, I'm not going to design for 1K, but I'll bet that this tube could drive it.
Since you're a measurements man, I suggest you set up to do what I used to do.
RUN YOUR OWN PLATE RESISTANCE CURVES. Then, you know what is happening for YOUR chosen specs & OP. points, etc.
To do this, I used a variable 0-650 VDC supply for the plate. I tapped a battery set at the voltages I thought would be within the ranges where I might want to operate the tube-- for the applied grid-bias.
At each grid bias point, the variable Plate supply had previously been set at ZERO. At each point, I measured the grid bias. Then, I upped the D.C. voltage on the plate in steps-- At each step, I measured both voltages.
Of course, plate current was being measured all the time.
I drew up a graph, and plotted all the op. points. (use commercial graph paper).
I did this on many tubes. NONE of them were ever perfect, some fell-in close to specs, (At SOME op. points), others did not.
EIMACS, in particular, were off quite a bit. I made about 25 plotted points for each tube.
This was more important when analyzing small-signal tubes, but I did it for all of them.
It's just another item for your basket of calcs. If you're going to do all this calculated stuff, then this will help you do it right.
---Dennis---
Dennis, I'm having trouble understanding what you are saying.
1. You said "...the advertised plate resistance is 800 ohms. I said ADVERTISED-- and yes, it will measure-out-- it's not wrong."
First you say the plate resistance is "advertised" as being 800 ohms.
Now this statement to me means that the plate resistance is something other than 800 ohms. But then you say it's not wrong?
So do you mean that the plate resistance is really 800 ohms?
If that is what you meant, why did you first say "advertised"?
So which is it? 800 ohms or something different?
2. You said "The JJ-2A3-40 will dissipate up to 40 watts, not crap-out at 15." but at 43ma and 250 volts that's only 10.75 watts of plate dissipation.
Why does it matter that the tube will do 40 watts if you are only going to use 10.75 watts?
As the tube operates along the load line, to the left of idle, the current goes up as the voltage goes down.
As the tube operates along the load line to the right of idle, the current goes down as the voltage goes up.
The plate dissipation stays (more or less) the same.
3. You said "Into 2.5K? That's coasting on a Banana Peel for it. This thing could drive 1K! No, I'm not going to design for 1K, but I'll bet that this tube could drive it."
Didn't you already say the plate resistance IS 800 ohms?
If the plate resistance is 800 ohms then a 1k ohm load impedance would cause a very vertical load line and the harmonic distortion would be very high because the operation to the right of the idle point, following the load line, will drop almost immediately into the non-linear region of the plate curves.
The fact that the tube will dissipate 40 watts does not change that. Only a lower plate resistance would change that or a MUCH higher idle current. The angle of the load line is directly related to the plate resistance not the tube's plate dissipation capability.
In all three of the above examples I really don't understand what you are trying to say.
Dennis, I've been to Montana and I know first hand that people from Montana speak English but when I read your posts I don't get the sense that you are speaking English. I don't know what language you are using and I don't understand what you are saying.
Do you?
In all honesty,
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hey! I get it, TRE!
NEVER challenge a published Dogma. Oh, but I do!
Bring ANY amp that you think is THE best, and I'll run it against this design-- the one that you prefer not to understand-- on our system at RMAF 2015.
This offer is open to anyone who brings a SET that is built right, and looks like it.... something the Demo room can justify showing to the public.
IF all of the people present choose yours, we will run it-- and name it's builder-- to the public.
If that happens, my design will go on the Display table, yours will get to play.
I will not vote unless there's a Tie.
---Dennis---
If there's a tie it means yours is just another 2A3 amp and doesn't require your vote. For that matter, if only 60% of the listeners prefer yours, it's just another 2A3 amp.
!
The Mind has No Firewall~ U.S. Army War College.
The answer is in my last post and is obvious-- a set of dogma proves nothing-- performance and longevity proves everything.
I've had enough of this crap. Good Day.
---Dennis---
this request either."Dennis, do me a favor?
With your amplifier playing music at your normal listening level connect a scope at the B+ end of the output transformer. Adjust the scope for the most sensitivity. Be sure to tell us what that setting on your scope is (volts per division). Do you see any waveform on the scope? If you do, what's the amplitude of the waveform peak to peak?"
Or any of the many other straight up questions I and others have asked you, over the years, where you never gave a straight up answer.
Thanks anyway Dennis. Have a nice day.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 01/30/15
This message has been moved to a more appropriate venue .
Edits: 01/30/15
What does any of that have anything to do with the questions I ask you?
Does the JJ 2a3-40 have a 800 ohms plate resistance or not?
What does the fact that the JJ 2a3-40 will dissipate 40 watts have to do with it's performance in an amplifier where the idle plate dissipation is only 10.75 watts?
If the JJ 2a3-40 has a plate resistance of 800 ohms how can it operate, with low distortion, into a 1k ohm load with the idle current at 43ma?
These are not technically hard questions.
Why can't you just give me a straight answer?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hey! I get it!
Bring ANY amp that you think is THE best, and I'll run it against this design-- the one that you prefer not to understand-- on our system at RMAF 2015.
This offer is open to anyone who brings a SET that is built right, and looks like it.... something the Demo room can justify showing to the public.
IF all of the people present choose yours, we will run it-- and name it's builder-- to the public.
If that happens, my design will go on the Display table, yours will get to play.
I will not vote unless there's a Tie.
---Dennis---
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