Strange buzz in a humbucker

[Artur pickupmaker]

I've made a pair of humbuckers (bridge and neck), then when I tested the neck humbucker had a strong buzz.
Today I opened its cover to test if a copper foil I put around one bobbin were grounded, thought it could not be grounded, but it was. The cover and base were grounded too. So I didn't discovered where was the problem.

The humbucker sounds great, it is not out of phase, and its bridge brother is good too but without this strange buzz. I used #43 wire in the bridge humbucker and #42 in the neck.
When I touch the grounded parts the buzz turns down but don't disappear.
Could be some problem in the wire?

[David Schwab]

Are you sure that both coils are working?

[Artur pickupmaker]

Yes, absolutely. I wired it to a mini switch to single coil/humbucker, the DC resistance is right for both as I planed.

[J S Moore]

Ground loop possibly. You may have nicked the insulation on one of the coductors, most likely the 4-conductor when taking off the outer insulation. Or the copper tape may be making contact with the coil lead and creating a dual path to ground or with the cover.

[David Schwab]

A pickup can't have a ground loop, it only has one ground.

But I also think a metal part that should be grounded on the pickup might be hot. Check the wiring.

[Artur pickupmaker]

I've never experienced a ground loop to create a buzz. All covered humbuckers I know are solded in two sides the baseplate and have no buzz.

David: I think "hot" is opposite to "ground". If I solder a part like a cover, baseplate or copper foil in the hot side I will really have a buzz. To avoid it this parts shall be grounded, then it will act as eletric shielding, reducing the hum. That's because metal cover pickups have less hum.

[David Schwab]

I've never experienced a ground loop to create a buzz. All covered humbuckers I know are solded in two sides the baseplate and have no buzz.

There is a myth that guitars can have a ground loop, which then causes people to use star grounding to get rid of a problem that doesn't exist. You absolutely need solid grounds and shielding to get rid of electrical field noise, which is that high pitched buzz you sometimes hear.

Even humbuckers are prone to that if they have ungrounded metal parts.

David: I think "hot" is opposite to "ground". If I solder a part like a cover, baseplate or copper foil in the hot side I will really have a buzz. To avoid it this parts shall be grounded, then it will act as eletric shielding, reducing the hum. That's because metal cover pickups have less hum.

I was just checking because it's a common wiring error I've seen a few times. Then you end up with "hot" metal parts that are meant to be grounded.

Well it sounds like you are doing everything right, so there must be an issue with the pickup itself, though I can't imagine what that might be.

[Artur pickupmaker]

I was just checking because it's a common wiring error I've seen a few times. Then you end up with "hot" metal parts that are meant to be grounded.

Well it sounds like you are doing everything right, so there must be an issue with the pickup itself, though I can't imagine what that might be.

I'm sure the metal parts are grounded, I've tested with the multimeter touching this parts and the rest of the ground parts, also the noise reduces when I touch the cover with the fingers. I don't know where is the problem.
It is possible the wire I used causes this problem? If it's not well insulated, generating many shorts, it would create a strong buzz like this?!?

I need to discover where is the problem or I'm gonna get mad, cannot wind other pickups.

[FunkyKikuchiyo]

Ditto David on the ground loops! You're my hero for bringing that up. I did a bit of research on this, it is a complete myth. For a ground loop to happen, two parts connecting to ground need to have different ground potentials. It is physically impossible to have a ground loop on a guitar. Well, if you had an active preamp in your guitar, and you had a power cable running out of that and it was plugged into a separate power line in the house than your amp, and given separate power line had a different ground potential, then yes you could have a ground loop. But since it all goes to the same amp, then you're getting a ground lollipop, not a ground loop. Ground lollipops, while perhaps delicious (I don't know, I just made up the term) don't create hum. As David said, the more continuity to ground that your shields/components get, the safer you are from them breaking free and being intermittent.

You CAN have ground loops with effects units that have external power supplies. This can be avoided by getting all your plugs onto one strip and going into one outlet.

Artur - does the buzz sound like typical 120 Hz hum that you get from lack of shielding, or is it a lower 50-60 Hz hum like single coils? Or maybe something different?

[David King]

It should be possible to see if there are breaks in the insulation using a VOM but an Extech AC meter would be even better.

Are both neck coils measuring close to the same DC resistance?

[David Schwab]

Ditto David on the ground loops! You're my hero for bringing that up. I did a bit of research on this, it is a complete myth. For a ground loop to happen, two parts connecting to ground need to have different ground potentials. It is physically impossible to have a ground loop on a guitar.

Exactly! There is no loop.

Sites like Guitarnutz have been confusing electrical field hum for ground loops. No wonder shielding the guitar fixes it.

I have also fixed grounding problems with redundant grounds... made everything nice and quiet. That's the opposite of what Guitarnutz says.

[Artur pickupmaker]

It's a bassy buzz, don't know if its 60 Hz or 120 Hz, its like a single coil hum.
I took off the cover but it kept on sounding.

The coils are 3 Kohm and 5 Kohm, when I turn the switch to single coil it gets even louder, but the noise is much louder than the expected in both cases. The bridge humbucker have higher DC resistance and mismatched coils (4Khom and 6 Kohm) and is very quiet, with no comparison.
I've made this two humbuckers toghether, the only difference is that the bridge one were wound with #43 wire and have no copper foil around one bobbin and the neck (noisy) were wound with #42 wire and have a copper foil.
As I said, everything is proppely grounded, the baseplate, the copper foil and the metal cover, even the polepieces of the single coil bobbin are.
I wonder if the #42 wire is the problem, it's the only different thing. But is it possible? Enyone there experienced a bad coil wire cause a hum?

[Joe Gwinn]

It's a bassy buzz, don't know if its 60 Hz or 120 Hz, its like a single coil hum.

That's probably a 120 Hz buzz. This implies that the noise is electrostatic in nature.

As I said, everything is properly grounded, the baseplate, the copper foil and the metal cover, even the polepieces of the single coil bobbin are.

How do you know? The only valid test involves measuring DC resistance with an ohmmeter (not an Extech LCR meter).

I wonder if the #42 wire is the problem, it's the only different thing. But is it possible?

Wire size cannot matter.

A broken coil wire can cause buzzy noise by reducing sensitivity forcing you to turn the gain up to get the music loud enough. What is the DC resistance of the coil?

[Mike Sulzer]

It's a bassy buzz, don't know if its 60 Hz or 120 Hz, its like a single coil hum.

Probably 180 Hz and higher. 60 Hz would be hard to hear, and usually odd harmonics are larger than even ones (but not always).

You seem to imply that you have only some of the cores grounded. Why?

On the question of whether guitars can have ground loops:

Here is a reasonable definition of ground loop from Wikipedia:

"In an electrical system, a ground loop usually refers to a current, generally unwanted, in a conductor connecting two points that are supposed to be at the same potential, often ground, but are actually at different potentials."

Suppose you put a guitar connected to an amp in a really strong electric field of power line origin. Suppose the guitar is shielded. Shielding blocks electric fields from the interior of the shielded area. This happens because the electric field that we want to shield out attracts or repels charge until a balance is achieved. For this to happen with this ac field, a current must flow in the shield of the guitar cable; this current provides the continuously changing charge. Since the resistance of the shield is larger than zero, a voltage developments across the two ends of the shield of the cable. This ac voltage appears in series with the output of the guitar and is a small source of hum. The emphasis is on "small"; it is not generally a problem. But it does seem to meet the definition of a ground loop.

It can be eliminated with a non-standard cable. The cable shield should be connected to only the shielding components at the guitar end and the amplifier chasis at the other. There should be two wires inside, the hot we normally use, and another wire from the "low" side of the pots, pickups, etc., what we normally think of as being grounded in the guitar. This wire should be grounded at the amp end near the low side of the cathode resistor of the first stage.

[FunkyKikuchiyo]

So, we're switching over to XLR plugs?