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In Reply to: RE: Dropping the Power Stage posted by Mr_Steady on November 23, 2014 at 11:13:58
It's connected as a triode in the schematic, too bad the data sheet doesn't cover that operation. But with 600mw output in pentode, you can bet on less in triode, which would be too little for an output stage, probably.
Sometimes I wonder why nobody builds a reverse logic amp, like a 45 driving
3 5687's in parallel or something like it. It's often said that it's the driver that gives the sonic signature of an amp, if so, then why not?
Ok sure, DC on the 45's filament (as a driver) but then the output stage should be quiet, even on very sensitive speakers.
Someday I'll come back to my box of 10's, and try a 10 as a driver, it's been done already by others.
Follow Ups:
GSH,
Thanks for the response.
Yes, and the 6AG7 pentode is a compromise also. Just a thought excersize.
" It's often said that it's the driver that gives the sonic signature of an amp, if so, then why not?"
I have heard that said many times, but I disagree with it. I have always found that the output tube had the biggest impact on the sound. That is, tube swapping the output tube resulted in the greatest changes in the sound, not swapping the driver tubes.
The reverse logic amp you describe sounds interesting. I have always like the idea of Broskie's 5 paralleled EL84 amp, with no driver stage at all.
I lost an auction on ebay for a little amp that had small step up transformers from a reel to reel as a driver stage, and paralleled 6SN7 for output tube with one watt output. This was before I went small, and I wish I had it.
Jamie
Big speakers and little amps blew my mind!
You sound as though you might be capable of a more scratch-built design. No need to stoop so low. :)
--------------------------
Buy Chinese. Bury freedom.
"Really? A Chinese Schematic???"
I knew that was coming! :) I knew there was no way I could get away with it twice. ;)
I've studied these schematics because they are so old-fashioned. They conform to the models in the ancient texts I've tried to learn tube electronics with. They have taught me enough to understand something about Gary Pimm's schematics, and Gary Pimm's scematics seem to be - the bomb.
"You sound as though you might be capable of a more scratch-built design."
The term, "Cluster F@#$" comes to mind.
"No need to stoop so low. :)"
I dig what you say on a lot of things. Howerver I guard myself never to underestimate the wisdom, intelligence, ingenuity, and shrewdness of the Chinese. For all I know resistors and capacitors are as cheap as dirt to this guy, as compared to CCS modules, and regulated DC filament supply modules.
Jamie
Big speakers and little amps blew my mind!
You might want to reexamine your world view, they wish to destroy you, comrade.
This coming from somebody who has taken a bullet in the head, and lived to tell the tale.Son, I was fight'n commies when you were at your mother's tit. But it wasn't the commies that got me.
How do I defend myself against my own President, and his minions in The Hive? They are more dangerous, because they can get their hands on me. The Chinese I'm afraid will just have to wait their turn. ISIS too. I know they are in a hurry and everything, but they have to take a number.
Let's just hope the Hive doesn't get the bright idea of importing 200 million Chinese in one day, then they would have the super-majority of unthinking, illiterate peasants they so crave. Actually, the Chinese probably aren't illiterate enough, they can do better than that.
Men and women who care about the ideals of the American Revolution will always be free to work themselves to death, and pay their taxes, while their children or grandchildren are being absorbed by the hive.
Sincerely,
Jamie
Big speakers and little amps blew my mind!
Edits: 11/25/14
There, you have it!Should your music amplifier be designed by the HIVE, or should it take a long, honest, hard look at how THE WHOLE THING can serve music?
Back to the HIVE-- they ARE right about current, voltage, and Network Theory.
But will they compare their best efforts to the best commercial units out there and figure out why those top commercial units are so good?
Can they improve on those? Some of them are very deviant! Some don't follow HIVE theory at all unless they have to (like voltage & current calculations, etc., which are Universal).
Who has improved on those "best" out there? Are they independent, or do they follow HIVE rules? A mixture of BOTH?
Will the hive-mentality beat-out the independent thinkers? Well, if they don't, it won't be for lack of trying!
Were the HIVE "rules" made to be broken, or are they designed to enslave/institutionalize your "correct" thinking? Remember: THEY are ALWAYS right! Aren't they? No? OH, OH!
STAY TUNED for more thrilling episodes.....
---Dennis---
Edits: 11/25/14 11/25/14
Dennis,
Nothing to say about this thread you posted to? You were the one who suggested dropping the power tube stage to make a smaller amp, and yet you didn't contribute to the discussion. Well, does a voltage amplifier make a good current amplifier?
Well, as regards the ongoing saga.
I read in the old textbooks I studied that the design equations they published were listed by the author as, "rules of thumb." That is, very general rules that would get you an amplifier up and running without a lot of headache. The designer was then free to tweak the circuit to their liking. If they tweaked to far in the wrong direction, then it would show up on their scope, or would do unpleasant things like oscillate or motor-boat. Rules-of-thumb are very different from unchanging law, as most people would agree.
IMHO, it takes a good engineer with good taste and good ears to design an exceptional SET amp. Anybody like me could get on TubeCad and a couple of other programs and design a mediocre amp. Who wants to listen to that?
Jamie
Big speakers and little amps blew my mind!
All excellent points-- no argument from me!
As far as running a driver stage into a speaker-- that would depend on how much power the driver stage in question-- has. If it's enough to drive your speaker, then an output transformer will convert what is primarily voltage swing into what is primarily current drive.
The answer to this question is simple: if a given amp stage has enough power to run a speaker, then why not do so-- why add more stages on to it??
If it doesn't have the power you're looking for, then you can add-on a higher power stage. That becomes one too many stages for an ideal amp, and is why we design 2-stage amps.
I didn't answer because I knew it would be blasted all out of context, and I didn't have time for a Dog/Cat fight over nothing at all!
---Dennis---
"All excellent points-- no argument from me!"
Somehow I think this should be immortalized.
So, is the power tube in a three stage amp also a voltage amplifier, and the OPT transforms it to current power? Sorry, no more basic questions. I'll stick to questions nobody knows anything about, like voltage regulation circuits. FETs loading the plate anyone?
Jamie
Big speakers and little amps blew my mind!
Power is usually expressed in watts, or volt-amperes. Watts equals Voltage times current: VA (watts)= amperes (current) X voltage.
---Dennis---
Thus endeth the lesson.
Big speakers and little amps blew my mind!
If that's the case, then I would suggest you guard Yyourself never to underestimate the wisdom, intelligence, ingenuity, and shrewdness of the Chinese.
The U.S. is special in the way we give money to those who wish to destroy us so we can drive SUVs and have cheap TVs.
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