Humbucker noise, except in middle position

[staggerlee]

Hi guys,
I have a SG Standard with a 57 + and 500T humbucking pickups. THe bridge pickup was replaced (by me). The guitar is exhibiting an almost single coil hum/buzz when used with higher gain. The noise largely disappears when the pickup switch is in middle position or when the guitar is held in an upright position (the tip of the headstock pointing to the ceiling).

I have redone a few solder joints that I previously did when I replaced the bridge pup, but to no avail. The noise is still there. Also, nothing happens when I touch the strings or any other metal parts. Any ideas on how we can diagnose this? By the way, I have another guitar with Filtertrons and it exhibits similar behavior although the noise (and pup output) is much lower.

Would that mean that it is environmental? Any ideas?

[b4nj0]

Obviously it makes the same noise with another amp / cable combo right?
So, moving straight on, what about actually grounding the strings- say by clipping onto the bridge or a machine head. This is distinct from touching the strings. Need to be aware of PME (protective multiple earthing) at least here in the UK anyway. With PME, the ground is not earth until it gets back to the sub-station and hence there is a finite voltage drop which can lead to an unwanted current flow in the event of a fault on the mains which would want to go to deck via your axe...caveat emptor, put on some wellies!
If that reduces the noise, it begins to look like environmental as you suspect. In particular- a horizontally polarised noise source. That would explain why you get a reduction in noise when you point it to the heavens, the cross polarisation would effect a 20 db reduction in the noise if the strings are acting as an aerial (antenna)
If you have an AM portable radio, you could wander around the house and your neighbourhood looking for the noise source. Remember the figure of eight radiation pattern from the internal ferrite aerial if you do this.
You did not state whether it affects both pickups, or just the one that you replaced. If it is the latter, the first thing I would do is to check the manufacturer's pick up lead colour code, just in case you have accidentally wired up using an incorrect arrangement that means you are only using the north or south coil alone. That might well explain why it disappears in the middle position- you may have a quasi humbucking arrangement in that position.
That's enough armchair theorising for now!
Steve.

[ashcatlt]

This kind of noise kinda has to be environmental. Somewhere along the lind you're picking up EM radiation from your environment. The question is where are you picking it up and can you do anything about it?

The first step is to try several different guitars through several different amps using several different cables in that same environment to be sure that it is actually the guitar. The fact that two different HB equipped guitars have similar noise would almost point to a cable or an amp issue, but the fact that it seems to change with guitar orientation points to the guitar itself. The middle position shouldn't be much different unless the pickups are out of phase, though it does provide a lower source impedance... Touching the strings should make a difference, though.

So, a couple things to check.

Have you confirmed continuity from bridge to jack sleeve? Did you disconnect the bridge wire during your modification?

Have you somehow connected a shield wire from the pickup to the "hot side" of the circuit? If the pickups have separate shield wires it is usually pretty obvious that these should be grounded, but some manufacturers will use one of the actual signal carrying wires, which might not be so obvious.

Does the noise change if you touch the pole pieces on the pickups?

Just throwing some stuff out there. It's kinda tough to sort this stuff over the Internet... It's quite likely that you're picking up noise in the control cavity. Shielding will probably help and definitely wont hurt.

Do keep in mind, though, that you'll never get rid of all of the noise in this system. There are ways usually to reduce it, and hopefully get it to a level you can live with, but it'll never be completely silent. Remember, too, that we're talking about a ratio of desired signal level to noise level. If you've got your amp franked to 11, and there's a noticeable buzz, but then you play and it sets off car alarms down the street... Also distortion of any kind compromises that s/n ratio by not letting the desired signal get much louder than the noise.

[staggerlee]

Just FYI, I'm a total electronics noob, so you quite lost me on this one
The issue is with both pups. Also, I haven't tried the guitar with a different amp but that's obviously a good idea.

How do you suggest I clip onto the bridge? Not sure what you mean by that? Do you mean run a wire from the back of a pot to the bridge like the grounding wire is supposed to do anyway?

I will try the AM radio trick and see if that points to any culprits.

[staggerlee]

Aug 1, 2013 12:02:30 GMT -5 ashcatlt said:

So, a couple things to check.

Let me run those diagnostics then and I will let you know. Thanks for the help.

[ashcatlt]

I'd submit that it really doesn't matter what the actual source of the noise might be. Even if you could track down and eliminate that particular issue there is noise everywhere! Maybe you never plan to play outside your house, but someday you may want to, and you'll likely be back where you started. Take the thing into a typical bar and...

[b4nj0]

I meant just to connect a wire temporarily to the (hopefully metallic) bridge because that is by definition connected to all of the strings, and then connect the other end to a known earth connection that is independent of the guitar / amplifier combination (a central heating pipe for example)
If the noise source is environmental, that should have an immediate effect.
Then we could begin to think about ways in which to deal with the noise if possible.

[staggerlee]

Aug 1, 2013 12:31:30 GMT -5 b4nj0 said:

I meant just to connect a wire temporarily to the (hopefully metallic) bridge because that is by definition connected to all of the strings, and then connect the other end to a known earth connection that is independent of the guitar / amplifier combination (a central heating pipe for example)
If the noise source is environmental, that should have an immediate effect.
Then we could begin to think about ways in which to deal with the noise if possible.

Thanks for the suggestion. It's just so happens that I haven't taken this particular guitar out of the house much and also, when rehearsing or playing out I don't use a lot of gain, so the problem may have been masked because of this.

At home I use a modelling amp, so I can crank the gain but not the overall volume.

I will get back after I've run the suggested diagnostics.

[staggerlee]

So here are some findings. I clipped a ground from the bridge to the neck volume pot. No changes in noise levels.
Just for giggles I unsoldered the stock ground wire from the pot to see how it will affect the guitar, and you guessed it, no changes whatsoever in the noise levels. I am wondering if the guitar is wired all wrong. I bought it used and I think some of the pots may have been swapped already.

[4real]

Could it be the jack is wired wrong...the hot being to ground and the ground being hot perhaps? Do you have a multimeter...perhaps a picture or trace the wiring might help too....