Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => EZ Board postings => Topic started by: Geezer on June 17, 2005, 08:50:13 pm
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Hoffman Amplifiers
> Tube Amp Building - Tweaks - Repairs
> Buzz when hands off guitar
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dazco6550
Junior tube assistant
Posts: 19
(2/9/04 11:04 pm)
Buzz when hands off guitar
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My new build, an 18 watter has that typical buzz when you remove your hands from the guitar, but much worse than most production amps. I have tried a million grounding schemes, and the amp is very quiet otherwise. I even added a .01 from the jack shield to chassis less than an inch away. Any ideas as to what else can be done? Thanks...
bluesbear
Hey get your own solder
Posts: 325
(2/10/04 12:13 am)
Re: Buzz when hands off guitar
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Does the buzz go away when you unplug the guitar cable from the amp. If so, you have:
1. Bad cable
2. Bad wiring in the guitar, or,
3. You're in the basement.
If this seems too obvious, I apologize. You'd be amazed how much time I've spent trying to cure "uncurable" hums only to have them disappear as soon as I take the amp out of the basement. Now, I haul them up BEFORE too much time has been invested!
Dave
dazco6550
Junior tube assistant
Posts: 20
(2/10/04 1:31 am)
.
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Thanks, but no.......it's none of those 3.
HStraub
Senior tube assistant
Posts: 214
(2/10/04 7:46 am)
Ground
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It sounds like the outlet you are plugged into isn't grounded correctly. Try a different outlet, or plug in an outlet checker. I have the same problem in my back bedroom....(I really need to fix that outlet) and I was SURE it was a good outlet until I plugged in the outlet checker. Bad ground.
dazco6550
Junior tube assistant
Posts: 21
(2/10/04 10:10 am)
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You're right. I don't have a grounded outlet here. But the reason i don't consider that the problem is that of all the amps i've plugged in here, none have been grounded of course, and none have made this much buzz.
Anyway, i found that it is apparently the way i've biased my preamp ! Maybe that makes little or no sense, but when i swapped back the original cathode filter and plate resistor the buz wennt down to almost nothing. I can only assume it's the extra gain the ones i like tonally cause thats amplifying it a lot. Too much gain in the initial stage i think. But i'm no amp tech, so i dunno for sure whats going on. In any case, i still need to find how to quiet it because i like the way it sound with the cap/resistors that are the noisiest.
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