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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Value of bypass capacitor on output. posted by Mark Kelly on April 13, 2004 at 22:24:53:
Just a guess, really. Both of the Gary's (Dahl and Pimm) have fooled around with the value of the CT-cathode bypass, and you know what, the value isn't critical at all. This is nothing like a parafeed cap (even though it looks like one), where tuning is a critical value dependent on trans inductance and Rp of the power tube.In this case, all that's happening is the bypass cap is actually *preventing* the amp from becoming a differential amp - omit it entirely, and yup, you have a diff amp - maybe not a great diff amp, no current source, just resistors. Why would I do that? Well, this is part of the style difference between me and Allen - I want the extra surge power that momentary Class AB offers, Allen doesn't. And yes, it sounds different. It can even be auditioned in an Allen-style amp - just have a switchable cap bypass for the current source, and listen for yourself.
So the bypass cap is there for flavor as much as anything - there's not much effect on the rest of the amp operation except peak current delivery capability, which is improved by the option of momentary Class AB operation.
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Follow Ups
- None of the above - Lynn Olson 00:38:34 04/14/04 (12)
- Re: None of the above - Henry Pasternack 14:23:09 04/14/04 (3)
- Various Bypass Stuff - Lynn Olson 02:17:54 04/15/04 (2)
- Re: Various Bypass Stuff - Henry Pasternack 14:55:58 04/15/04 (1)
- Good Question - Lynn Olson 15:31:32 04/15/04 (0)
- the style difference between me and Allen... - Allen Wright 09:04:05 04/14/04 (0)
- OK I'm just interested in intermodulation cancellation of odd harmonics. - Mark Kelly 01:27:38 04/14/04 (6)
- Deep waters there, good luck - Lynn Olson 01:50:27 04/14/04 (5)
- Yes - Mark Kelly 02:55:09 04/14/04 (4)
- Variables to play with ... - Lynn Olson 04:31:24 04/14/04 (3)
- I want to be shipwrecked and comatose... - Mark Kelly 05:32:39 04/14/04 (2)
- I hope you (and all the rest of us) succeed - Lynn Olson 01:56:55 04/15/04 (1)
- Your loop discussion was what rekindled my interest. - Mark Kelly 04:02:42 04/15/04 (0)
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