There's a problem... somewhere

Acidic · #1 07-25-2011, 11:53 PM

I've had my 90-something Peavey Fury for just over 2 years now. I've always played through a small like 35w Samick amp. A little while back I joined a gigging band and bought an Acoustic B200 200w combo amp. Since getting the larger amp I've noticed a static-type hum coming from the bass when I don't touch it. When I touch the strings it stops. A grounding problem, I know. But I've racked my brain trying to figure out where. Here's where it gets interesting. Today I got a new pre-wired pickguard and went to install it. The pickguard didn't fit my bass body so I took all the hardware out and replaced it onto my existing pickguard. So the issue is: brand new pickups, brand new pots, brand new jack, all wired correctly. When the noise still happened I tried different cables, still did it. I plugged a guitar into the amp, nothing. So I know it's in the bass somewhere. I pulled everything apart and tried different bridge grounds and it still did it. Once the bridge is grounded the noise lessens but when I touch the strings (or anything else metal on it) it stops completely. Turning down the highest EQ knob on the amp helps kill it too, naturally. I just can't figure out what the problem is. Any ideas?

SGD Lutherie · #2 07-26-2011, 07:26 AM

You might need shielding in the bass. It could also be your amp. Does the amp have a three pin AC plug? Are you plugging it into a grounded receptacle?

Pickups and pots and such have nothing to do with electrostatic noise.

Acidic · #3 07-26-2011, 10:48 AM

Quote:

Originally Posted by SGD Lutherie

You might need shielding in the bass. It could also be your amp. Does the amp have a three pin AC plug? Are you plugging it into a grounded receptacle?

Pickups and pots and such have nothing to do with electrostatic noise.

Alright let's see, shielding in the bass I have sorta thought about, is that something I could do myself? The amp does have a 3 prong cord but it is very possible that the outlet isn't grounded well. Kinda seems like it was a 2 prong outlet with an adapter in it. Thanks for your input, I'll be sure to try out a different outlet first

Stealth · #4 07-26-2011, 12:20 PM

Try a different outlet first as that's much more important - namely, so you don't get shocked.

Secondarily, shielding is something you can easily do at home, there's plenty of pictorials right here on TB. I've done the procedure once and it went without a hitch, improved the situation immensely, documented it in a thread.

Also, check if the bridge is grounded - you haven't mentioned it anywhere, and I assume you tried it, but again, double-check the bridge grounding wire, solder or copper-tape it to the bridge underside and solder it to the output jack's sleeve terminal.

Acidic · #5 07-26-2011, 12:35 PM

I thought I had mentioned the bridge thing already, I tried it all externally to make sure the bridge was getting a proper ground. Tried it with multiple wires to be sure that it wasn't a broken wire somewhere. The pickguard thing I got has a terminal block so there's no soldering for the grounds, they just screw into the block. I did test it across the bare bottoms of the pots to be sure though. I plugged our rhythm guitarist's Les Paul into the amp and there was a bit of hum but not much, which I guess can be expected with a guitar in a bass amp. I'll definitely try another outlet since I don't recall it being so prominent when we play shows. I'll also look for your thread on DIY shielding (unless you can post a link, which would be awesome too). Thanks guys for your help and quick responses

Stealth · #6 07-26-2011, 12:43 PM

My bad - you did mention bridge grounds. I prefer soldering the ground wire to a bridge, but I usually use a bit of sandpaper on the bridge first to make sure the solder will get a solid contant.

As for the shielding, this is how I did it. The J pickup is as quiet as a beetle now.

Acidic · #7 07-26-2011, 02:49 PM

Where do you get the copper foil?

96tbird · #8 07-26-2011, 10:46 PM

Any good guitar shop, or eBay if youre not near one.

Acidic · #9 07-26-2011, 10:54 PM

Cool thanks. There's not a 'good' guitar shop near here. I'll check eBay. Any certain kind to recommend?

96tbird · #10 07-26-2011, 11:18 PM

guitar shielding tape, conductive adhesive. No need to solder, just overlap pieces to complete ciruit.
5 ft Adhesive Back Copper Shield Tape for Guitar & Bass | eBay

Acidic · #11 07-26-2011, 11:24 PM

Thank you very much

Acidic · #12 08-01-2011, 10:27 AM

Just thought I'd post an update on my issue. I plugged my amp into a different outlet and ta-da! no hum whatsoever. We played through a couple songs and between songs I noticed it was suddenly doing it again. Sure that's a little odd but here's the strangest part, one of the guitars was now doing it, too. Nothing about his setup changed at all, we were plugged into different outlets, and his has never done that whatsoever. Thoughts on this one?