Grounding Humbucker?? shielded lead wire, Star Grounding

[rustgl]

I have questions about grounding Humbucker.


Where is it better to ground the grounding wire in a Humbucker?

1. To the baseplate in the Humbucker itself?

2. To the Star Grounding?



If I use the copper shield around the bobbins and a shielded lead wire, where should the shield be grounded?
1. To the ground wire and then to the baseplate in the Humbucker?

2. To the ground wire and then to the Star Grounding?

3. The ground wire and the shielding should go separately from Humbucker and then grounded to the Star Grounding?

Thank you!

[newey]

We first must define our terms. "Grounding wire" is ambiguous.

Every coil, HB or SC, has two wires coming from it that carry signal. For convenience, we arbitrarily designate one as "hot" or "+", and the other as "-" or "ground". In a HB, with two coils, there are typically 4 wires, two for each coil, plus the shield. However, old-style "vintage" HBs often have the two coils internally connected, and thus have only two visible wires.

Some also have a third wire, commonly called a "shield", which is not carrying signal, but is meant to reduce noise by shunting it to ground. Often on vintage HBs, the shield and signal ground wire are combined into a braided wire that surrounds the insulated "hot" wire.

So, when you say "grounding wire", I assume you are talking about the non-signal-carrying shield wire, and not speaking of the signal-carrying wire often called, for convenience, a "ground".

Pickup shield wires are always attached to whatever place one is using for a grounding point. If using star grounding, then it would be attached to the star grounding point. The only exception is if one has an old-style HB with the single conductor plus braided shield- the shield will usually connect to the grounding point, but might connect elsewhere depending on the wiring scheme being used (since then the shield wire also carries the "-" pickup signal).

[rustgl]

newey, thank you for the answer.


But the main question is what wire to solder or not to the baseplate of the HB.

So, as I understand, please correct me if I am wrong:


1. Humbucker with 2 lead wires + and – and the ”–“ one is acting as a shield and carrying signal. It is soldered to the starting wire in the bobbin and at the same time to the baseplate.

2. Humbucker with 2 lead wires + shield. The “-” wire is soldered to the start of wire in the bobbin. The shield is soldered to the baseplate on one end (not to the start of wire in the bobbin) and to the Star Grounding on the other.

3. Humbucker with 4 lead wires + shield. Two “-” wires are soldered to the start of wire in the bobbins. The shield is soldered to the baseplate in one end and to the Star Grounding on the other.

[newey]

Correct as to all three. In #1, where the shield also carries signal, it might not get wired to the star ground point, if, for example, one was wiring to a phase switch or series/parallel switch. However, if that were the case, best practice is to separate the shield wire from the signal negative, by disconnecting the signal/shield wire from the bobbin and running a separate insulated signal wire from the bobbin, leaving the shield alone connected to the baseplate. I've never tried this, but those who have done so said it wasn't as tough to do as it sounded.

As long as one was going in there, one might as well just make it into a 4-conductor HB.

[JFrankParnell]

I thought we decided star grounding doesnt apply, in a guitar?

[newey]

I thought we decided star grounding doesnt apply, in a guitar?

We pretty much concluded that, under the vast majority of circumstances, star grounding would make no difference as to noise levels. The idea, as John Atchley put it originally on G-Nutz1 was that "ground loops" could potentially induce noise, and that star grounding was useful because it eliminated the ground loops inherent in the traditional pot-to-pot daisy-chain grounding.

But ChrisK and others pointed out that, since the ground loops were so short and involved so little length of wire, they were highly unlikely to cause perceptible noise, especially compared with the length of wire inherent in your pickup coils- which are known to be the major source of noise. Of course, one cannot make absolute statements about such things, or one will hear the inevitable "but what ifs . . .". "What if my band is gigging in a dive bar with dodgy electrical circuits, 14 fluorescent lamp fixtures with bad ballasts and 20 or so neon beer signs lining the walls? There might be noise from ground loops there." And, of course, one can never prove that some such combination of factors might not be a problem. Theory would seem to indicate noise could be induced into the signal in such a fashion, so it can't be proven that it doesn't have some non-trivial effect under extreme conditions.

My two cents, anyway.

But star grounding is a good wiring practice in and of itself. Most consumer electronic goods routinely employ some type of "star grounding" whether noise is a consideration or not. Most such goods will employ a "grounding buss" of one sort or another, which is effectively (and electrically) the same as a star ground.