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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: Tube Fixed Bias posted by Audio Space being on December 1, 2006 at 22:44:13:
If I read this right, you wanna take the fixed bias off a portion off the winding of your main B+ supply.Thats an absolutely terrible idea and I am surprised no one has pointed it out. Have you thought about what that fixed bias supply does and where it is used?
Its on the GRID of the audio tube in the final stage, mixed with the music signal. Soooo........ANY noise or pertebation of the fixed bias supply is "seen" as an audio signal to the dumb triode grid. It is necessary, if you are into GOOD designing using fixed bias, to absolutely have a TOTALLY separate supply, and it can NEVER ever be half-wave rectified.
Thus, you are stuck with a small power trannie for the bias supply alone, and a quad of highly unstressed schottkys for rectification, preferably into a choke input filter, and well-filtered, as the best approach, albeit a compromise.
All that said, cathode bias is, on the basis of sonics alone, is preferred by these ears.
Jeff Medwin
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Follow Ups
- Re: Tube Fixed Bias - drlowmu 12:31:02 12/07/06 (0)
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