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04 Apr 21 - 08:17 AM (#4100706) Subject: Tech: Biasing valve amps From: Bonzo3legs I have a 1980s Carvin X60 valve combo amp, which is loud - very loud for its specified 60 watts. Probably about time for a service and possible replacement of the filter capacitors and rebiasing to preserve performance for DIY noise drowning duties!!! |
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04 Apr 21 - 08:18 AM (#4100707) Subject: RE: Tech: Biasing valve amps From: Bonzo3legs Ah, my question is are there any sound characteristics which indicate that rebiasing is necessary? |
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05 Apr 21 - 02:55 AM (#4100816) Subject: RE: Tech: Biasing valve amps From: BobL What's "rebiasing"? I've been an electronics hobbyist since the days when all amps were valve driven, and I don't recall the term. Is it setting the DC bias on a push-pull output pair in order to minimise crossover distortion? In which case I'd have thought you'd only need to readjust it after replacing the output or driver valves. |
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05 Apr 21 - 05:31 AM (#4100821) Subject: RE: Tech: Biasing valve amps From: Bonzo3legs I've since found out there is more than 350 volts flying around inside my amp, so I think I'll leave it a to a guitar amp technician!! |
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05 Apr 21 - 05:50 AM (#4100823) Subject: RE: Tech: Biasing valve amps From: GUEST,Phil d'Conch Better safe than fried. Did you ever get those noisy controls fixed? A Pictorial Guide To Biasing Carvin Tube Amplifiers WARNING: During the course of biasing, you will be exposing yourself to dangerous voltages up to 400+/- volts D.C. If you feel at anytime that you are not sure of what you will be doing, don’t do it. It is recommend that you practice each step several times with the amp’s power cable unplugged so if you make a mistake, you will not pay for it with a damaged amplifier or a damaged body. |
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05 Apr 21 - 05:59 AM (#4100825) Subject: RE: Tech: Biasing valve amps From: Bonzo3legs Yes I managed to fix all but one - the reverb level which I replaced, I never use the reverb anyway. |
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06 Apr 21 - 03:15 AM (#4100942) Subject: RE: Tech: Biasing valve amps From: BobL Thanks Phil, from your link it appears I guessed right. With valve equipment one recommendation when working on live circuits was to keep, if possible, the other hand in your pocket. I've had the odd belt in my time, and shed no tears at consigning those days to history. |
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06 Apr 21 - 06:00 AM (#4100956) Subject: RE: Tech: Biasing valve amps From: ripov can you still buy those 9.0v grid-bias batteries? As BobL says one hand in pocket with all things elactric and TEST BEFORE TOUCH! |