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In Reply to: Re: feedback on b+of circlotron posted by TUBEVIBB on September 7, 2006 at 10:32:52:
I think you are talking about the 1K ohm resistor that Ralph shows going across the two banks of caps that filter the LV supply (that is, the +/-140V supply for the output tubes). I built my amps from a schematic supplied by Ralph, and I therefore dutifully also installed that resistor, using a 5W or 12W Mills. There is no voltage across that R because both halves are at the same potential, so really a high-wattage resistor is/was not necessary. I never thought about it as a "feedback" element in the circuit. I think Ralph once told me that he was ambivalent about the necessity for it, but I left it in my highly modified MA240 amps.That said, I am not sure what you need "help" with. You seem to have done fine by yourself. If you want reassurance, OK, you got it. Your observation that the 1K ohm resistor makes an important sonic difference is very interesting; never experimented with it myself. I always assumed that the 1K resistor was used in all Atma factory-built products, but I would not know for a certainty.
Follow Ups:
Lew the 1K resistor does provide negative feedback and lowers the output impedance. At least that's what I found when I built my home brew circlotron OLT amps.Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
It's been ages since I looked at the schematic, so could neither confirm nor deny that the 1K R provides NFB.
I HAVE PUT A CAP 6.5MF ON THE 800 OHM LIKE SILK,SAME AS ALL FEEDBACK I BY PASS.BUT I MUST SAY I CANT LIVE WITH IT.BUT THE CIRCLOTRON WE R FEEDINGBACK +/- OF SAME CHANEL.I ASK FOR HELP ON THE DEFF. BUT MAY NOT BE FAIR .I CAN MAKE CHANGES DAYLY. BUT THANKS FOR ALL INPUT I HAVE B&W 802M 804M 805N SNELL MAIII ACOUSTAT 3 ML LS3 ADS 810
...is easier to read, and the use of all-upper-case text looks as if you're shouting.
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Tin-eared audiofool and obsessed landscape fotografer.
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