Grounding Question (Technical)

Hello all,

Is there any noise benefit to be had by separating your signal grounds from your shield grounds? I know some builders prefer doing it that way.

I'm going to be adding a baseplate to my bridge pickup shortly and I figured while I'm in there I'd desolder the bridge ground from the negative lead of the pickup and run it separately to ground.

I was thinking similar to the guitarnuts.com wiring, but without the capacitor:

http://www.guitarnuts.com/wiring/shieldedinnards.gif

Basically run the signal grounds to a small ring terminal and the shield grounds to the back of the volume pot.

Any thoughts?

There is no point. The guitarnuts capacitor is supposed to be a protection against accidental shock. If you are not adding that big cap, don't bother rewiring anything.

You may read some posts about "ground loops". You can't have a ground loop in a guitar. A ground loop is very loosely defined as "multiple paths to ground." People mistakenly think this refers to anything but a star ground, in a guitar.

There is only one path to ground, in a guitar, and that is through the jack. A ground loop refers to current leaving, and coming back in, then going to ground in a different path. You can get that when you use two amps, but it isn't the guitar that is causing it.

There is no point. The guitarnuts capacitor is supposed to be a protection against accidental shock. If you are not adding that big cap, don't bother rewiring anything.

You may read some posts about "ground loops". You can't have a ground loop in a guitar. A ground loop is very loosely defined as "multiple paths to ground." People mistakenly think this refers to anything but a star ground, in a guitar.

There is only one path to ground, in a guitar, and that is through the jack. A ground loop refers to current leaving, and coming back in, then going to ground in a different path. You can get that when you use two amps, but it isn't the guitar that is causing it.

+1 Jim is right. Aside from the small benefit of some shock protection, this circuit does nothing else. The currents in a guitar are too small to create other artifacts, as well.

Most of the nasty grounding problems of the past were due to the primitive grounding of old amps - 2 prong AC with 1 side grounded to the chassis via a large cap. Yep, that can cook you. But modern 3-prong grounding (into proper outlets of course) eliminates most of the hazards our forbearers had to endure.

I heartily recommend that all working amps be properly grounded, no matter how old.

All right thanks guys. I suspected as much.

There is a practical benefit of having a separate ground wire to the baseplate since it frees up your options in terms of phase reversal or series/paralell wiring.

Otherwise I always wondered how it could be so wrong to put an extra ground wire connecting the three pot shells, which are at the same time connected to a foil shield or metal control plate, if that's how Fender has always been doing it.

There is a practical benefit of having a separate ground wire to the baseplate since it frees up your options in terms of phase reversal or series/paralell wiring.

could you talk some more about this? on my current build, i'm gonna use the superswitch to add series and series/out-of-phase settings ... i knew you had to reground the neck pickup, but had no idea about the bridge pickup having its own grounding issues. you're suggesting adding an additional ground to the baseplate? what's the optimum grounding scheme for this situation?

To accomplish phase reversal and/or series switching, it is only necessary to have one pickup that can be reversable. Typically, in two pickup wiring schemes that involve series and/or phase reversal, one pickup's ground wire is permanently connected to ground. In a Telecaster wiring scheme, that pickup is usually the bridge pickup. The neck pickup is usually the pickup that has a seperate ground wire for its cover. It is never necessary to be able to switch the phase of both pickups, since "out of phase" is important only when both pickups are used at the same time. (Were the phase of both pickups to be changed, the pickups would be in phase with each other.) Even if you wanted to wire a four-way switch, for the series sound, and a phase switch, to reverse the phase of the neck pickup regardless of the position of the selector switch, you still would only have to provide a seperate ground wire for the neck pickup's cover. The bridge pickup's ground lead would still be permanently connected to ground.

My discussion assumes the bridge pickup is of the vintage ilk, which has a base plate that is connected, by a jumper, to the pickup's ground wire. In this arrangement, the guitar's bridgeplate is automatically grounded. If the bridge pickup does not have that base plate, the bridgeplate must be grounded seperately.

thanx, Jim -- that clears a lot up, the issues being discussed higher up in the thread having to do with adding a baseplate. mine will come with the baseplate, hopefully thoroughly grounded.