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RE: What I don't get...

Hi Gusser,

You ask this :

"How does Dennis and Drlowmu reproduce the subtle "micro dynamics" with the signal riding on top of rather high power supply ripple? If you are going to try and reproduce "micro" anything in an audio signal you need the background noise as low as possible. That would mean virtually no measurable AC ripple just as a start."

OK Gusser, good honest question, 'deserves an answer.

- - - - - - - - - - - - - - - - - - - -

We see the 2A3 SE output stage, in a DC two stage amp, as somewhat like a unity buffer. (A mu of 4 triode driving a 2.5K to 8 Ohm step-down trannie.)

This means we are hearing mostly the driver tube, be it a 7B4 in Dennis' case, or half a Telefunken smooth plate 12AX7 in my case.

The driver tube's B+, therefore, must (as you have surmised above), be SCRUPULOUSLY optimized and it IS, "an engineering tour de force" compliments of Dennis' total design.

The two stage DC amp beneficially allows us to have a super clean, low ripple B+ driver supply, with only about a millivolt of AC ripple on it, with no power supply cap in the amp over 50 uF.

Further more, this low ripple driver supply is shunt regulated with a ONE PART no-negative-feedback shunt regulator. The shunt draws at least 15 TIMES what the audio circuit draws, so perturbations of audio content, the musical information, has VERY LITTLE interaction with the shunt regulated driver supply.

Additionally, there are other power supply optimizations employed, that I am simply not free to divulge, but my post gives you a legitimate answer to what you asked, I believe.

I hope this made sense to you :

(a) about a mVAC B+ ripple in the first stage and

(b) a 15 times shunt regulator,

.... helps keep the music intact as to micro detailing, etc. Layout, wiring, also helps.

I am not able to offer any more details of his circuit, but the whole amp is a "total design", in every sense of the word total. His supply is located "all over the amp", and is integral with the audio circuit. It has been very well thought-out, in 1989, by Dennis Fraker. My friend Dennis, he IS the "real deal".

Gusser, book a plane now, for RMAF October 2012 Denver, and catch the show. We would like to meet you.

Jeff Medwin, audio amateur

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