Re: That so depends...

Posted by Ray Moth (A) on April 15, 2005 at 01:57:09

In Reply to: That so depends... posted by A on April 14, 2005 at 11:38:23:

Russ's reply is great and I wouldn't add to it except that he omitted to mention the Van Scoyoc cross-coupled splitter. I've never found a clear description/critique of this splitter, not even in the venerable Radio Designer's Handbook. Mr. Stan White, who used it in his 1951 POWRTRON design, seems to think that it's the best but doesn't explain why.

I'd like to use the cross-coupled splitter sometime. I prefer an all-differential amp. I'd like to get the full gain from both halves of the splitter. It would also be nice to avoid having to lose voltage in the tail, as happens with a resistor or a pentode CCS (yes, I know I could use a SS CCS but I've never had any luck with them there "three-legged fuses" in tube circuitry).

The cross-coupled splitter offers good balance, good gain, good PSRR and the whole of B+ to play with. It's also very easy to apply negative feedback to its input. Its big draw-back is that it can't tolerate a high-level signal, because of the way the drive is applied from the cathode follower in the first half to the grid and cathode of the second part (the part that has the gain). However, provided that we use a sensibly high voltage and low current for the tubes concerned, our bias should be high enough to cope with a typical line-level signal of up to 2v RMS. The consequence of this limitation is that a cross-coupled splitter must be used early in the amp circuit, namely, as the input stage, which dictates an all-differential design.

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Follow Ups Full Thread

Topic - Phase Inverters - BillyJack 20:39:55 04/13/05 (14)

Re: Phase Inverters - Eli Duttman 05:57:49 04/16/05 (1)

Re: Phase Inverters - Ray Moth 01:22:42 04/27/05 (0)

Re: Phase Inverters - Tre' 18:20:48 04/15/05 (0)

Re: Phase Inverters - nerdorama 11:10:19 04/15/05 (0)

That so depends... - A 11:38:23 04/14/05 (9)

Re: That so depends... - Jim McShane 11:19:16 04/15/05 (0)

Re: That so depends... - Ray Moth 01:57:09 04/15/05 (7)

Optimation and ITT used Van Scoyoc - Scholl 11:53:10 04/16/05 (0)

I disagree about Vmax and balance. - Mark Kelly 00:01:56 04/16/05 (1)

Re: I disagree about Vmax and balance. - Ray Moth 01:10:37 04/27/05 (0)

Re: van Scoyoc - Mahatma Kane Jeeves 13:16:16 04/15/05 (1)

Re: van Scoyoc - Ray Moth 01:07:39 04/27/05 (0)

Thanks, I did miss one didn't I? - Russ57 10:57:14 04/15/05 (1)

Re: Thanks, I did miss one didn't I? - Ray Moth 20:38:05 04/26/05 (0)

Follow Ups

Re: That so depends... - Ray Moth 01:57:09 04/15/05 (7)

Optimation and ITT used Van Scoyoc - Scholl 11:53:10 04/16/05 (0)

I disagree about Vmax and balance. - Mark Kelly 00:01:56 04/16/05 (1)

Re: I disagree about Vmax and balance. - Ray Moth 01:10:37 04/27/05 (0)

Re: van Scoyoc - Mahatma Kane Jeeves 13:16:16 04/15/05 (1)

Re: van Scoyoc - Ray Moth 01:07:39 04/27/05 (0)

Thanks, I did miss one didn't I? - Russ57 10:57:14 04/15/05 (1)

Re: Thanks, I did miss one didn't I? - Ray Moth 20:38:05 04/26/05 (0)

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