Tracking down Hum in one out of 3 pickups

Kay Dallben

New member
Hi all,

I'm looking for some advice and guidance in troubleshooting some hum in my guitar.

I've come across 3 distinct hums so far, but they've all been only significantly noticeable out of my neck pickup, and I was hoping for some assistance / suggestions of ways to potentially isolate the hums.

1) What I assume is a ground loop hum: I am testing through a Line6 Guitarport into a laptop. When the laptop is plugged into the power bar, I get an extra hum that is moderate in the Neck pickup and barely noticeable in the Middle & Bridge pups. I don't think this is really avoidable when playing through a computer, and the software "hum reducer" takes care of most of it.

2) Interactions between Player and grounded bridge/shielding/pots. I assume this is Me introducing into ( / compensating for) environmental noise the circuit: touching the shielding, ground lugs, backs of pots, inner ring of the jack, etc. I see this in two incarnations:
a) when I have the Neck pickup completely uninstalled from the guitar:
i) I introduce a new buzz when I touch any of the grounded points. I also notice this is the same/similar buzz as when I type on the laptop at the same time the guitar is plugged in.
ii) I seem also to introduce/balance a buzz depending on where my hand is overtop of the electronics. (I had the pickguard upturned on my desk, and holding my hand above the electronics a few inches away the guitar got completely quiet, but when I moved my hand away, a buzz returned. Buzz got louder when I moved my hand closer to the electronics, so I figure that's Me interacting with a hot lead. (I'm sure you've accidentally touched the hot lead and gotten that screech in your ears, too.)
b) with the neck pickup installed, I notice a slight buzz when I do NOT touch a ground, and no apparent effect when I hand-wave.

3) Neck position hum: So this third 'distinct' hum is by far the loudest. It only happens with the neck pup in use. When the neck pup is in use (positions 1, 2 and when I flick the n-pup ON switch), there is a loud buzzing hum. I've tested both with the pickguard installed in the guitar and out of the guitar, and here are a couple observations concerning orientation and location of the pickguard:
a) When the pickguard assembly is out of the guitar, if I have the pickguard oriented electronics-down, the hum is louder. I turn it face up, the hum lessens noticeably (sounds kind of like I'm taking the bass out of the hum?), but not all that significantly. Orienting it perpendicular to the earth and rotating causes some effect to the hum, some softening occurs in some angles.
b) When I put the pickguard assembly into the guitar (which is ostensibly shielded, and is 'grounded' directly from the bridge (tailpiece) and copper shielding tape to the inner ring of the output jack) the neck-only hum increases - it increases both with flipping the pickguard to electronics-side-down and when actually putting it into the shielded cavity.
Regarding Position isolation: It really only seems to be coming from the Neck pickup. In position 1, it is loudest, quieting slightly when I switch the Neck pickup from Series to Parallel with the push/pull. It also quiets slightly when I switch to position 2 (Neck+Mid), and further if I do that and put the neck pup in parallel. Position 3 and 4 has no hum at all. Position 5 (bridge-only) has the teeniest of whispers of what could be that same hum (I didn't notice it at all until I focused hard to see any difference in the positions).

I'm wondering if the neck pup, which is a Vintage Rails Neck - they have an odd half-half coiling and are "made to be wired in parallel" - is humming loudly in just one of the coils. So I tried some things:
- Hooking up the Vintage Rails Neck pup with Black to lead out, white and red spliced and tied off together, green and bare to ground. No difference - the hum is still loud.
- Hooking up the single-coil pup that came with the guitar produces the exact same hum!
The weird thing is before I did the rewire to swap the pots for push/pulls and do the parallel/series switching, I don't remember the neck pup humming - it was just the #1 expected hum from a computer and #2 my body making or stopping some noise when I touch grounded strings/bridge.


Extra information:

"Amp" setup:
I don't have an amp. I'm plugging in via a Line6 Guitarport into my laptop.

Guitar Wiring Setup:
A) H H H. each is a single-coil sized seymour duncan pup.
- specifically they are Vintage Rails Neck, JB Jr., and Hot Rails. They are all probably in the 8 year old range. It's hard to remember exactly when I got them, and they were all 2nd hand off craigslist at that point anyway.
B) I use a 5-Way Strat Switch in normal config. From 1 being closest to the Neck to 5 being closest to the bridge: (1,2,3,4,5)->(N,N+M,M,M+B,B)
C) Pups are each wired into dpdt switches to change between parallel and series wiring. These are push-pull pots, with the DPDT wired up like this Hot lead in each case goes from the DPDT to the 5-way switch per Seymour Duncan Website SCH SCH SCH 1 vol 2 tone wiring
D) I have a DPDT switch which I'm using as a SPST switch to add in my Neck pup to any position. This looks like this with more leads obviously on the 2nd pole of the switch.
E) Pots are configured as Master Volume, Neck Tone, Middle Tone. Middle Tone has no cap on it. Neck tone has a 0.047 uF cap that previously existed on the stock tone pot.
F) The guitar itself is an Ibanez Blazer Series from 1980 (Maybe Korean?), with its whole cavity shielded with what looks like copper tape. Continuity across all the tape and the bridge is fine using a multimeter.



I appreciate any help you could provide!
 
Re: Tracking down Hum in one out of 3 pickups

Make sure all the components including the switch, mini toggle, and pots are grounded with wires.
 
Re: Tracking down Hum in one out of 3 pickups

If you are touching it and it gets louder, you have a ground connection somewhere going to output. A side note is that ground loops cannot occur in guitars. So long as every metal is connected someway to ground and none of the ground connections form a connection to any of the hot wires or lugs, you will be fine.
 
Re: Tracking down Hum in one out of 3 pickups

If your laptop is grounded to the mains ground & the mains ground isn't floating then you should not get buzz from humbucking pickups when recording. Atleast I don't when I use a zoom u22 interface.

If your are getting good continuity from the strings to the sleeve of the guitar cable, then check your main's ground for faults.

It could also be some device that is plugged into the main's in the apartment building(if you are in one) that is causing this problem. Try the guitar at another place as well.

That was quite a lot of typing for a first post, good job detailing the issue
 
Re: Tracking down Hum in one out of 3 pickups

First is get longer cables and get as far as possible from the computer. Then deal with what buzzes remain.
 
Re: Tracking down Hum in one out of 3 pickups

Thank you very much for your advice, all!

Clarity on Hum #3:
So this Neck-Pup-only hum is very similar to the Hum I'd get when 1/4 cable plugged into "amp" but not into the guitar. Is it at all possible for electronics inside a guitar to act on the same principle, but only with respect to a particular pickup? Is it possible for a humbucking pickup to "work" but still pick up a hum like a single coil?
- Since I had swapped out the Vintage Rails with a single-coil, and gotten the same hum in neck position, and since playing both mid and the Vintage rails together (position 2) lessens the hum slightly (alluding to the 'hum-cancelling' positions on a standard strat by playing two single coils together), and since putting the Vintage Rails into: Black->Hot out, Green&Bare->Ground, Red&White spliced and tied off, is it possible there's a problem with the Vintage Rails pup? If so, is it possible to test it further at home, with a multimeter?


Clint 55: Grounding all components:
- So the wiring diagrams have all gray/green from the humbucker pups soldered directly to back of Volume pot. Because of my use of the DPDT push/pull switches, I have each pair of gray/green soldered to the back of the respective pot, which is in turn connected by a wire to the back of the volume pot. I've used insulated but unshielded wire to run all the ground wires, and all the wires going between pots and the switches.

Could either of those two things (or both) be a problem, even though there's no Extreme hum coming when either of the Bridge or Middle pups are active without the Neck active? Should I instead run grounds directly to the jack instead of to the volume pot and THEN to the jack?
I have the shielding grounded directly to the jack. Should it instead be grounded to the back of the volume pot?

The mini-toggle switch I use for the neck pup add-in has no ground connection. It only connects the output of the DPDT neck pup switch (which will either have Black only or Black + White if in parallel) to the 5-way switch Common lug, like so. I could misunderstand you, so could you clarify if that particular switch needs to be grounded, and if so, which lug - or are you talking about the Housing of the switch itself, which I think is in contact with the pickguard shielding.

Christopher: If you are touching it and it gets louder, you have a ground connection somewhere going to output.
Right, so this is part of Hum#2. So because it only gets louder when the neck pickup is Not installed and I touch a ground (it gets quieter when the neck pup is wired to the DPDT switch and I touch a ground) that suggests to me that the ground connection going to output is on the DPDT switch. Does that make sense to you as well? Or is that a "not necessarily, the connection going to output could be anywhere"
Is there a multimeter test I can use to check? Continuity - I feel like that wouldn't work because that would always say a ground and a hot are connected cause the circuit is closed?

Hank: (Mains Ground) So this is hum #1. Laptop definitely is grounded, 3-prong plug, uses an AC adapter into a power bar into the wall socket. What is "good continuity" - is that taking a multimeter, using the continuity test, and getting a solid tone, or is there a particular reading I'm looking for? I'm also not particularly familiar with the concept of floating vs non-floating grounds, but I'll google that. Are there noticeable symptoms of my main's ground having a fault?

Also, just to ask about your Zoom U22 - Do you notice a difference (buzz/nobuzz) when you use it on battery power vs. through its own AC adapter? Are you recording through a laptop, or something not-also-plugged-in like a tablet?

I'll definitely have to check the guitar at another place, but for the moment that's not immediately feasible. I'll back-pocket that for troubleshooting that #1 hum. I assume trying a different circuit in the apartment is also worthwhile, so I'll likely do that in the near future as well.
 
Re: Tracking down Hum in one out of 3 pickups

You can use the continuity setting or lowest resistance setting to see if you get zero ohms reading. Sometimes an outlet may not have a ground wire connected or broken. There are those wall socket tester things with leds that lit up in a particular pattern of the wall socket is wired wrong. Those are cheap & sometimes built into power strips. What you get with your neck pickup, is something I get with one of of my hss strats that isn't shielded. Some hours of the day it's quite bad & sometimes it doesn't occur at all. I even moved the pickups to a different guitar that was factory shielded with paint & the pickups didn't buzz, they wére noiseless singles too. Since you mentioned you are getting proper continuity between the grounds & copper foil shield in the cavities, I'm not sure what to recommend there. Maybe the problem lies in the location.

Anyways, about the zoom u22. I don't use it for software sims. When I connect it to my laptop or PC, it receives power through the usb cable connecting it, so the guitar gets grounded too via the pc ground.
 
Re: Tracking down Hum in one out of 3 pickups

In my experience, not using wires to ground any of your components increases noise. People frequently leave out mini toggles and selector switches from their ground circuit for some reason and you mentioned you have. So yes you have to scuff up the housing of your mini toggle, use some flux, and get a ground wire soldered to it. Also do the same to the base of your selector switch and I bet you'll hear a drop in noise. Also, the order in which you ground does not matter, as long as everything leads to the jack's ground.
 
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