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OTL, Output Transformerless Amplifier User Group.

RE: How about an actual experiment?

"I am assuming one would insert a very low value resistor in series with the cathode of one of the tubes, and put the scope across that. This would give a direct view of the current flowing through that tube."

I'm not sure it would. I think AC current flows in a circle that includes all the tubes. I could be wrong about that.

"I agree that the outcome seems inevitable, since there simply isn't room for anything else to occur. I just feel that one clear trace showing the waveform of the current flowing in a single tube would put a stop to the endless debating about whether it is or isn't class A."

I couldn't agree more.

"What seems a shame in all this is that it detracts from the much more important point that it is a beautiful amplifier that apparently sounds superb. "

Yes it is a shame and the amplifier does sound great. It's just not Class A in the true sense.

Transcendent Sound, makers of OTL amplifiers, makes it clear that their amplifiers (and most other OTLs) are Class A/B.

The paper from Transcendent, while using some language that I don't totally agree with, makes the same points.

A Class A amplifier needs to idle at 1/2 the total needed peak current [that's 1/2 per bank. If you add the idle current of the two banks the amplifier needs to idle at the total needed peak current].

It takes 3.86 amps peaks to make 60 watts into 8 ohms so there needs to be 1.93amp idle current per bank or 241ma. per triode.

That just can't be done with a 6as7g.

Thanks for your input.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"



Edits: 08/27/11 09/20/11

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