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ground noise problem from the bridge.

Yvon

Yvon

Nov 2, 2000
4,462
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Montreal, Canada
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#1
My lecompte is very clean sounding, I mean no noise at all (unless I unse only one pick up in single coil, but that's normal).
But when I go to my guitar player place the noise is really really bad.
No matter what pick up I use. In any configuration.
But if I touch the bridge, the noise stop.

What would be the problem?
The place? ( he have many computers, tv etc in his basement)
A bad ground somewhere in the bass?


Thank you


Yvon
 
#5
Yvon said:
My lecompte is very clean sounding, I mean no noise at all (unless I unse only one pick up in single coil, but that's normal).
But when I go to my guitar player place the noise is really really bad.
No matter what pick up I use. In any configuration.
But if I touch the bridge, the noise stop.

What would be the problem?
The place? ( he have many computers, tv etc in his basement)
A bad ground somewhere in the bass?


Thank you


Yvon
Click to expand...

Clearly there's a source of interference there. I think your bridge is simply ungrounded. Get a little piece of flexible wire and wrap one end tightly around a part of the bridge, and the other around the outer metal part of the plug going to the amp, for instance make a tight loop twisted around the plug's long shaft, and then cram the plug into the bass, capturing the loop between the jack on the bass body and the plug. You want to temporarily connect the bridge to the outer (long = Ring) part of the plug. You can also use a little cable with clips in both ends. It's just for test, though I've seen clip leads used in the studio to get the noise down. If you get rid of most of the noise this way, you will need to make a permanent replacement for this little wire.

There should be a wire under the bridge running into the cavity where the controls are, and it should be soldered there. Sometimes the wire gets disconnected, you can see where, and you can repair it by soldering it back on. It needs to connect to the common ground point or the outer ring of the jack where the plug goes in. On some basses they just left that out. In that case you have to take the bridge off (you already have, to look) and drill a hole under the bridge into the cavity, and run a wire through the hole, leaving a length of flattened stripped uninsulated wire under the bridge, screw the bridge back down capturing the uninsulated part of the wire either with a screw or just by laying the bridge on it (scrape or sandpaper the bottom of the bridge where the wire will be captured to make sure you get a good connection), then solder the other end to the common ground point in the cavity, or just to the outer lug on the jack that the amp lead plugs into. You have to examine the jack as it's mounted and determine which solder lug connects to the so-called "ring" that the long part of the plug contacts, and not the "tip", where the small end of the plug contacts. If you have no experience soldering, have someone do it who has some electronics experience. If your little wire experiment worked, this will do the same thing (and look better than a piece of wire hanging there) and you don't have to keep your hand on the bridge :D.
 
#7
Yvon said:
My lecompte is very clean sounding, I mean no noise at all (unless I unse only one pick up in single coil, but that's normal).
But when I go to my guitar player place the noise is really really bad........But if I touch the bridge, the noise stop.
Click to expand...
Sounds like there is some kind of problem with the AC power at your guitar player's place, possibly a bad ground. 1st thing I'd do is get a Canadian version of one of these outlet testers...
Invalid Link Removed
to check for any power wiring issues. You could have a potentially dangerous situation there.
 
#9
jazzeddie1234 said:
I found this site really useful in understanding what is going on with hum and stuff. Even had specific instructions for my Fender MM bass

http://www.guitarnuts.com/wiring/shielding/bass.php

Make sure you read the section on safety as grounding the strings can be risky when pluged into an unknown/dubious sound system
Click to expand...

In the US, we have 240 volts coming into buildings, and it's split 120/120 with a center tap, some outlets getting one phase, and others getting the other. They still share ground and the center tap of the incoming 240 that is called "neutral", and that should be at ground potential. There are a myriad ways for things to get messed up. My favorite was a landlord of mine who rewired something and I ended up with the hot and neutral reversed on one outlet. When I plugged in equipment in one outlet and the other, and connected the two with a cable that carried ground, the ground lead became red hot and smoked, followed by many other more costly things smoking. So, yes, it can be fun.

I still think it's possible for a missing bridge ground not be be obvious in an electrically "quiet" environment. I've played a lot of older instruments with no viable bridge ground wire, and they don't buzz in every environment, so I wouldn't automatically exclude that possibility in his case, even though the bass is quiet at home. Clearly something is different at the guitarist's place in any event, and that should be looked into, yes, carefully, but to check the bass' bridge ground by adding a quickie temporary jumper is such a simple test that it makes sense to try it.

Useless fact #8765890. Do you know that the ground at the top of a mountain can be several hundred volts off from ground at the base? On ski lifts and gondolas, wiring and steel rope runs from bottom to top, and if you break a ground, you can get zapped purty good between the two grounds. I can imagine all sorts of funky musical scenarios with Leningrad Cowboys playing a concert on a mountain. Oh, yes, I remember, their bass player was already dead.
 

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