# Buzz in JCA20H?



## Emohawk (Feb 3, 2006)

Hey folks,

I picked up a JCA20H when they first came available when the intro pricing deal was still on. Neat little amp, but I do have one issue with buzz somewhere in the pre-amp (I think). The buzzing is there even without a guitar or cable plugged in. It's not 60hz hum. It's a higher pitched buzz, which is why I think it may be a pre-amp gound or interference somewhere in the front end. I've swapped the tubes, tried different cables/guitars, etc with no effect. 

Has anyone else had the same issue? Just wondering if it's something common in the layout/design or if I may have a cold solder in a ground somewhere.

I did clean up the wiring in the power/HT section & the OT primaries/secondaries. Man - talk about spaghetti! Ridiculously long runs in the AC & B+ lines, OT primaries untwisted & bundled with the OT B+, heater secondaries untwisted, etc. Also the folks who assembled the thing seem to think more solder = better. I'm sure I sucked out enough to build another amp just in the half dozen connections I re-did. After tidying things up the noise floor seems to be a bit lower, and it certainly looks more civilized in there.

They also used a common ground for the pre-amp & power amp, which I don't personally like. I prefer to have a separate pre-amp ground on the opposite end of the chassis. In the amps I've built that seems to help with noise/hum. Not sure if I can easily change that. They also grounded the AC to the same ground point as everything else, and that I'm definately going to change. I thought it was a North American standard to have a separate ground point for the incoming AC?

Thanks,
Kirb


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## Greg Ellis (Oct 1, 2007)

I'd love to see some before and after shots, or even just "afters", if you feel up to it.


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## Emohawk (Feb 3, 2006)

I don't have a before, but here's an after. There was so much wiring on the left that you couldn't see the chassis underneath. Looking at the scrap on my desk that I cut out, I'd say it's 4-5 feet of wire hacked out. I could probably shorten the orange/yellow for the PT primaries too. Don't know why I didn't do that... It's done now!


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