Is this a ground loop?

[frank57]

I put in some new pots in my old Swede,(the original ones, fell apart one by one) but looking at the wiring,
Isn't this a ground loop on the back of the pots? The red wire originally was not there.
That was put in by someone else.So the original grounding was slightly changed.
Bit hard to follow the wiring so I took a best guess.
I had to put in a paper in oil cap too.
The original cap lead broke.
The schematic is actually after this particular one was built.(77 vs. 74)

[HotBluePlates]

Strictly, yes. But the size of the loop, as well as the currents which flow through it, determine whether the loop will cause any issues. The loops seen within most guitars' wiring harnesses cause almost no problems. You're more likely to notice hum picked up by the pickups themselves.

[frank57]

So on a tube amp, a loop would cause far more problems because of the voltages?
It could simply be the pickups like you say.They do sound great but I don't think they're potted like
the new ones with wax and all that.
It is somewhat noisier than a new guitar but depending how you're facing the amp.
I was thinking of removing wire 2 between the tone pots.Would that do anything at all?

[VMS]

Get away from the amp and face the audience   

[frank57]

Always a good idea
But even facing away from the amp, you have to be careful with this guitar.
Depending how you turn more noise.This guitar is a little noisier.
I think all humbuckers tend to do this to some extent.
Move the guitar around, more or less hum?

[HotBluePlates]

If you face any humbucking pickup at a t.v., monitor or power transformer, it will pick up a buzzy hum. The closer you get, the louder the noise. The more gain your amp has, the louder the apparent buzz/hum. You will notice a hum when facing a particular way, and less/zero when turned about 90 degrees on an axis (or two).

So on a tube amp, a loop would cause far more problems because of the voltages?

No, ground loops are about currents flowing through the loops, and interacting with each other. This happens more readily when 2 points that should both be "ground" (or 0v) have slightly different voltages. This could happen when you make a large loop; one "0v" point might not be the same as another 0v point.

Big loops or wiring paths can also be bad within an amp, because they can act like an aerial or antenna. If the circuit is high impedance, and has a large loop hanging off a tube grid, you will likely pick up hum and/or oscillation. The coupling could take place due to radiated fields due to large a.c. current, or it could take place due to electrostatic induction due to large a.c. voltages.

I was thinking of removing wire 2 between the tone pots.Would that do anything at all?

I don't think so. Cut and see if you want. But most modern Gibson guitars are wired with all the pots on a sheet metal plate (a ground plane), but the grounds for the pickups are still made by soldering the braid shield to the back of the pots. Is that a ground loop? Yeah, probably, but no new Gibson guitars have ground loop issues.

[frank57]

My newer hagstrom does the same thing when you move it around
but the noise and hum are far less.
If the pickups were not potted maybe that might be causing more noise?
Something must have gone right anyway because I did lower the noise a little.
There seemed to be a bit of exposed wire where the wire from the pick up and the one going to
the bridge volume pot  are taped together underneath the pickup so I pushed the tape a bit to cover it.

When I was soldering I did lift one of the wires going around the pots at the neck volume pot.
There was no change in the hum when I pushed it to the top of the pot.
Is the wire between the tone pots even needed for grounding?