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In Reply to: Music or Ripple ?? That is the question..... posted by drlowmu on March 12, 2007 at 10:00:54:
I'm workin on mine! I need to build a separate front end supply though.
I'm putting together the main B+ now, for the output stage (2A3). I thought I would need "less" ripple on the driver? Can I use a similar two stage low everything supply and not have noise on my front end?
I was going to use a low mu triode: 6P5, 6J5 or better (IMHO) triode wired C3o which has a Rp of 2K while mu of 17, (the 6J5 we should have had). I have some 1660 IT's, also plate chokes, assuming only these two coupling methods would work with this PS? I guess loading the driver with a resistor "kills" the point of the PS? Jeff, please tell more about your driver and the problem solving you went through thanks.
Follow Ups:
Hi bobbij,Read my prior post, only 20 mVAC to the 76 stage, with a two stage filter, so YES, do it the same for your front end. Use a Mills MRA-12 ( one or more ) shunt bleed across the B+. No problem. Use a real triode !!
No, loading the plate with a good resistor is fine, and is wider band than any choke or IT.
Thanks Jeff, OK, I thought the BW was "wider" with a resistor, but wasn't sure the dcr was contrary to the rest of the effort. I too, like the "idea" of "pure" triodes. I like 6p5, 6j5, etc...But the C3o is a surprising devise, a little on the bright side, perhaps due to the low Rp. Now, to load a 6P5 "properly" I'm assuming a 50K plate resistor, so I'll have a 250V drop at 5ma idle current, so I'd need at least 450-500 VDC to start with?
Hi,
Please kindly re-read Dennis' comments in my post of his most recent two emails, where he clarifies and refines this subject, second email, under point ( H ).Design with low DCR except for the audio circuit, there, High DCR to allow it to swing !!
Got it ??!! URL follows.
Jeff Medwin
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