Tracking Down Source of Single Coil Hum

Discussion in 'Tele-Technical' started by RandomPrecision, Mar 19, 2020.

  1. RandomPrecision

    RandomPrecision TDPRI Member

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    I'm playing a G&L ASAT Special, with the jumbo MFD pickups. I do much(*) of my playing in my office. Recently I've become increasingly annoyed with single coil hum. Before I go getting a noise gate or some kind of active device, I was wondering if there's any chance I'll be able to track down the actual cause?

    Some observations:
    • I recently used copper tape to completely line the back of the pickguard, pickup and control cavities. I verified continuity of all the tape to ground, I'm confident it's reasonably well shielded now.
    • I have another identical ASAT Special that is NOT shielded, but there doesn't appear to be any difference in this particular hum between the two guitars.
    • It's virtually non-existent with a clean amp, at least at the bedroom volumes I'm using.
    • The hum is slightly worse, but still bearable, with my overdrive pedal (Boss OD-3).
    • It's unbearable with my Rat. As long as the pedal volume stays below roughly 11:00, it's not too bad... But (outside the hum), the pedal sounds better with the volume up a bit!
    • There's no hum with humbucker pickups (or with my ASAT on the middle position, i.e. both pickups (presumably in series, like a humbucker)).
    • The hum doesn't change if I touch the strings or any metal part of the guitar.
    • The hum does go down as I roll the guitar volume down (and no sound at all with the volume control all the way down).
    • If I spin my body around, it does get a little better at a couple positions. But it's a very narrow band where the hum is minimized.
    • I also tried holding the guitar parallel to the floor (perpendicular to my body), both with the pickups pointing up, and also pointing down, and spinning around 360 degrees. With the guitar like this, I could not find any position where the hum went away.
    • I tried shutting off everything in my office - PC, monitor, stereo amp, printer, etc. Basically anything I could turn off (except for the amp), I did turn off. No change.
    • My understanding is that AC wiring is typically the most common cause of this kind of hum. But in theory, all my in-wall AC wiring should be shielded with steel conduit. My house is only a few years old, and code in my area requires AC lines to be run in steel conduit.
    • The outlets in my office are all on a dedicated circuit (i.e. don't share a circuit with anything like a refrigerator or furnace motor).
    So I guess the easiest solution is to just turn down the Rat pedal volume, but I'd be really interested to track down exactly what's causing the hum. Something must be causing some kind of EM field, but I can't figure out what that would be.

    I suppose I could methodically start killing breakers in the house until the hum goes away. That might annoy my family though, anyone have any ideas for a less invasive way to track this down?

    Thanks!

    (*) With the social distancing, I'm now doing all my playing in my office. Band is on hiatus for the time being. :(
     

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  2. TelenTubes

    TelenTubes Tele-Meister

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    Also interested. Making a bag of popcorn now.

    Have a few guitars that do this. I have learned that certain pedals, like my compressor, will magnify the hum if you're not playing (I guess that's what pedals are supposed to do). THAT told me that the hum is coming from the guitar at least, lol.

    The guitars that give me the most hum have LOUDER hum near the amp, and the hum is reduced when I touch the strings on one, so that tells me grounding/shielding might improve the situation? But I'm an accountant, not an amp tech, lol.
     
  3. RoscoeElegante

    RoscoeElegante Friend of Leo's

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  4. E5RSY

    E5RSY Doctor of Teleocity

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    This is what I've used live for a couple years now. I find it pretty indispensable now. I've never heard the overtones you occasionally read about. Most of the complaints of that nature seem to come from the uber-high gain crowd...and that ain't me.
     
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  5. rangercaster

    rangercaster Poster Extraordinaire

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    Fluorescent lights maybe ??? Or other issues ... dimmer switches also ...
     
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  6. RoscoeElegante

    RoscoeElegante Friend of Leo's

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    Me either. I notice it only on certain fairly high reverb or delay settings. Nothing problematic, as the hum without it--e.g., at gigs with neon lights or just bad power--is otherwise so frustrating.
     
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  7. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Sounds pretty normal to me.
     
  8. Switchy

    Switchy Tele-Holic

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    This right here.
     
  9. jvin248

    jvin248 Poster Extraordinaire

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    .

    Are you shorting wiring inside the cavities?

    Did you replace the wires to the jack with shielded cable? Fender uses two separate wires, I suspect your G&L does too. $100 Gibson-Epiphone guitars ship with shielded cable to the jack. It's important.

    Aluminum flashing tape does a better job of noise reduction than copper. Yes, copper is used a lot, there is research out there for cell phones/computers/etc that aluminum is better.

    Covered pickups are important. Tele neck, lipstick, and chrome covered LP humbuckers cut out a lot of other noise.

    If the noise totally disappears when going series/parallel on the guitar then it's the pickups not the chassis wiring/shielding.

    .
     
  10. TimTam

    TimTam Tele-Holic

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    Guitar noise diagnosis is not a very well developed science, with no real readily accessible, definitive measurement tools. Having said that, these guys at least take a categorized, noise-frequency-specific, directed approach to tracking it down ...
    https://www.pedalsnake.com/blog/category/the-noise-manual/
     
    Last edited: Mar 20, 2020
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  11. johnDH

    johnDH Tele-Meister

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    I'm going to take that as a clue and suggest checking that the strings are grounded via the bridge. As a test, put some kind of wire from bridge to jack outer barrel.

    When you touch grounded strings, you ground yourself and you stop being such a source of the electrical noise problem and instead become part of the solution.

    It works well unless you have to play an open E11th chord.
     
  12. Wallaby

    Wallaby Tele-Holic Silver Supporter

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    I'm watching this with interest, I don't have answers to the same issues.
     
  13. RandomPrecision

    RandomPrecision TDPRI Member

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    I agree, these are the likely culprits. I'd also add big AC motors (refrigerators, HVAC). But what is the range on these would-be noisemakers?


    That was my original plan, but I ended up not doing it. I did tightly twist the wires that run from the cable jack into the control cavity. I agree, shielded is much better though.

    Interesting. Though I would think copper is certainly better than nothing, and from what I can tell, at least for this particular scenario, copper isn't doing much, if anything.


    Yup, my thoughts exactly. That's why I was hoping I could actually track down whatever is causing the hum in the first place.


    Strings are definitely grounded. I checked with my DMM, no resistance between strings and outer barrel of cable jack.
     
  14. Treehouse

    Treehouse TDPRI Member

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    Clear nail polish on the tops of the pickup pole pieces was the icing on the cake for me after completing other shielding and grounding best practices.

    Scotch tape over the pickups will have the same effect and easy to try before you go through the trouble of giving your guitar a mani peti.

    this was a recommendation of Seymour Duncan. Ymmv

    edit: I clearly didn’t read the OP but maybe this will still give someone something to try lol
     
    Last edited: Mar 21, 2020
  15. fretWalkr

    fretWalkr Tele-Meister

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    A computer monitor is a likely source of hum. When you "spin your body around" is the angle in relation to a screen?

    I noticed that when I record on my DAW the monitor proximity causes my single coils to hum. I have to sit at a certain angle to keep it quiet. The vintage tone is what I'm after so I'm ok with adjusting my position or the laptop angle on my desk. I'm used to it.
     
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  16. RandomPrecision

    RandomPrecision TDPRI Member

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    My computer monitor doesn't seem to have an effect on this... I tried unplugging it entirely (along with all the other electrical equipment in my office), and nothing changes. Also, with the monitor turned on, directly facing the monitor (or 180 degrees from that, i.e. with my back to the monitor) is actually the least-noise spot.

    I just spent a little time setting up the amp in different parts of the house, and walking around seeing where the noise got better/worse. There is a corner of my basement where there is a lot of electrical current being drawn: furnace, computer rack, battery backup sump-pump, alarm system panel. I could reduce the hum noticeably if I unplugged the server rack and the power supply to the alarm panel (which happens to be a fairly large transformer). If I unplug the sump-pump, the inverter kicks on (i.e. running from battery), and that definitely changes the tonality of hum through the guitar amp. Interestingly, the furnace kicked on while I was doing this, that didn't seem to make a difference (at least not an obvious one). As I mentioned above, all the structured wiring is in conduit (basement is unfinished, so this is trivial to verify)---but the cables to all this equipment are actually pretty long. In theory, there may be some clever way to twist or coil those cables to have the fields cancel out. When we get around to finishing the basement, that whole area will become a little utility closet---might be interesting to see if there are cheap ways to shield the whole area.

    When I'm in the office, it seems like if I angle the guitar a bit, directly towards this corner of the basement, the hum gets louder. That's actually what sent me down to the basement in the first place.

    Might just have to live with it, or try the EHX HumDebugger.
     
  17. Antmax

    Antmax Tele-Meister

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    I had the same kinds of problems. It's fairly normal with single coils. Couple of things you can do is make sure you have a decent isolated power supply. I spent years avoiding spending $100+ on one. Tried various things that cost less than $15. I really didn't believe it could make that much difference.

    When I finally caved in and got a OneSpot CS7 it really did make a noticeable difference. It didn't go away entirely but the noisefloor was mostly gone on the clean channel and volume seemed roughly halved in the hi gain channel.

    Only other thing I found that improved things was going wireless with a Line6 G10. That removed the guitar cable, when you have the cable plugged in then your guitar plus cable together are basically an antenna. Wireless won't play nice with some old pedals like fuzz and others that use those antiquated circuits with Germanium transistors in since the receiver has a buffer in the output.
     
  18. jdiego

    jdiego TDPRI Member

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    If a proper shielding on the pickguard, pickup cavities and a shielded cable from the circuit to the jack isn't enough for you, then I would recommend only three things:

    - improve the ground of the wall outlet
    - get a noise cancelling stuff from Ilitch (or build it yourself)
    - switch to humbuckers
     
  19. Wallaby

    Wallaby Tele-Holic Silver Supporter

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    I think I am reading this wrong, but clear nail polish and scotch tape to eliminate RF?



     
  20. 1300 E Valencia

    1300 E Valencia Friend of Leo's

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    If the noise goes away when you select both pickups everything is normal.
    You can't eliminate single coil pickup noise 100%.
    But some need to discover this for themselves.
     
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