Single coil hum, how to eliminate?

[Cunamara]

Well, think about the original DeArmonds: pickup completely surrounded in metal, shielded wire to control box, which was also a complete metal shield around the pots and caps. This was connected to the ground side of the cord to the amp. These were single coil pickups and usually much lower noise than most Strats and Teles or P90s/CC pickups.

The "hot" signal doesn't travel through the shielding, it travels on the "hot" wire to the tip of the jack plug. The purpose of the shielding is to keep extraneous noise out of the hot signal by draining that noise to ground. In most cases it is a partial Faraday cage, so not completely successful. The DeArmonds were the most shielded singles coils I know of. Also, according to Bill Lawrence, aluminum foil was better than copper at blocking RF interference from dimmer switches, etc. If you look under a Strat pickguard, the control area shielding is aluminum.

I think the largest contributor to noise is the transformers in the amps; it would probably make more sense to shield the amps than the guitars. My metal-boxed AI Clarus 2r causes the least noise of any of my amps, but it also doesn't have a big lump of iron for a power transformer either.

[KirkP]

So I tried the LEHLE and does not help. But I have other uses for it so don't regret getting it. Tried to buy an EHX Hum Debugger but they are out of stock everywhere. Sweetwater doesn't expect to receive more until July. Anyone know where one is available?

Also, this hum is the type that gets louder and softer depending on the position of the guitar. Touching the strings has no effect. And even at its lowest level, the noise never goes away entirely. I'd like to record using this guitar so hoping to find a way to silence it completely, if that is even possible with a CC pickup.

So it’s definitely a hum, not a higher frequency buzz?
Here’s a 60 Hz hum.

In Europe it could be 50 Hz.

If it’s a hum, I doubt shielding would help much. I think you need to keep the pickup as far from power transformers as possible and experiment with orientations of the guitar and/or any gear with power transformers to minimize the magnetic coupling between them. Coupling might be minimized when the loop of your pickup is orthogonal to the loop of the power transformer, but it might take trial and error to find that orientation.

Equipment with toroidal power transformers will couple much less hum to your pickups, but you’ll probably only find them in solid state equipment.

I’ve only used an EHX Hum Debugger briefly. Some folks say it changes the tone, but many others like it so it seems worth a try if the suggestions above don't help. I think works by subtracting the AC hum in the wall socket from the signal coming from the pickup. That’s why they tell you that you must use their proprietary power supply.

[rpjazzguitar]

Well, think about the original DeArmonds: pickup completely surrounded in metal, shielded wire to control box, which was also a complete metal shield around the pots and caps. This was connected to the ground side of the cord to the amp. These were single coil pickups and usually much lower noise than most Strats and Teles or P90s/CC pickups.

The "hot" signal doesn't travel through the shielding, it travels on the "hot" wire to the tip of the jack plug. The purpose of the shielding is to keep extraneous noise out of the hot signal by draining that noise to ground. In most cases it is a partial Faraday cage, so not completely successful. The DeArmonds were the most shielded singles coils I know of. Also, according to Bill Lawrence, aluminum foil was better than copper at blocking RF interference from dimmer switches, etc. If you look under a Strat pickguard, the control area shielding is aluminum.

I think the largest contributor to noise is the transformers in the amps; it would probably make more sense to shield the amps than the guitars. My metal-boxed AI Clarus 2r causes the least noise of any of my amps, but it also doesn't have a big lump of iron for a power transformer either.

Good point. I had assumed that if you wrapped a pickup in copper or aluminum foil and grounded the foil, then the p/u wouldn't work. That the magnetic field wouldn't penetrate the foil and therefore couldn't sense the string.

But, the D'Armond pickup is surrounded by metal and works fine. Perhaps somebody can explain the physics of that.

[John A.]

Good point. I had assumed that if you wrapped a pickup in copper or aluminum foil and grounded the foil, then the p/u wouldn't work. That the magnetic field wouldn't penetrate the foil and therefore couldn't sense the string.

But, the D'Armond pickup is surrounded by metal and works fine. Perhaps somebody can explain the physics of that.

My understanding is that only ferromagnetic materials can block a magnetic field). So copper or aluminum (or any other non-ferrous metal) won't block the magnetic field. The vibrating string can still interrupt the pickup's magnetic field and induce a current in the coil. Grounding is irrelevant to that.

A grounded shield can block electro-magnetic radiation in some frequency ranges (typically RF), but not in the frequency range of AC current. This is why single coil buzz is so difficult to neutralize, especially in rooms where there are multiple sources of AC-frequency EMR coming at the pickup from different directions.

[Len R]

Happy to report that the EHX Hum DeBugger solved the problem. Arrived today, plugged it in, turned it on, and the hum disappeared. Does it affect the tone? Maybe it takes just a touch of the shimmer off of the trebles, but it is barely perceptible, and if you are playing in any situation other than a silent room you would not notice the difference. At least with this pickup. Could not say if would have more effect on the tone of other pickups. Also, am using the normal setting, no need for the strong setting. Thanks for the suggestion!!

Len

[Brmr]

That’s awesome!

[KirkP]

My understanding is that only ferromagnetic materials can block a magnetic field). So copper or aluminum (or any other non-ferrous metal) won't block the magnetic field. The vibrating string can still interrupt the pickup's magnetic field and induce a current in the coil. Grounding is irrelevant to that.

A grounded shield can block electro-magnetic radiation in some frequency ranges (typically RF), but not in the frequency range of AC current. This is why single coil buzz is so difficult to neutralize, especially in rooms where there are multiple sources of AC-frequency EMR coming at the pickup from different directions.

A Faraday shield will attenuate electromagnetic fields if the thickness sufficiently exceeds the skin depth. The skin depth depends on material conductivity and frequency. For example, at 60 Hz, I think the skin depth of copper is around 1/3 inch, so a thin layer of copper foil probably won’t do much for hum. But the buzz from LEDs, dimmers, wall warts, etc. has a much higher frequency content. That’s why I consider foil a solution to “buzz” but not hum.

[John A.]

A Faraday shield will attenuate electromagnetic fields if the thickness sufficiently exceeds the skin depth. The skin depth depends on material conductivity and frequency. For example, at 60 Hz, I think the skin depth of copper is around 1/3 inch, so a thin layer of copper foil probably won’t do much for hum. But the buzz from LEDs, dimmers, wall warts, etc. has a much higher frequency content. That’s why I consider foil a solution to “buzz” but not hum.

I'm out of my depth with the physics/EE of it, but my experience is that every single-coil pickup is susceptible to noise from dimmers, LEDs, wall warts, neon or fluorescent light ballasts, etc. Some do better than others, but they all buzz to some degree under some conditions.

[rpjazzguitar]

Thanks to the physics guys who responded!

[Cunamara]

Agree. I always learn a lot here!

[whiskey02]

Try a different outlet/circuit as well.
I've got one outlet connected to a circuit with some can lights on a dimmer. Turning the lights off makes a huge difference. Plus, just plugging into an outlet in the other room instead does as well.

Otherwise, for gigs... I use an EHX hum debugger. But I only need it once or twice a year.

I believe a light dimmer switch in the room is THE loudest buzz inducer there is.

Side note: Dig your playing, my respect sir.

[Ukena]

I just pulled out my Eastman 905CE CC, which has a similar Lollar Charlie Christian PU as Len's Eastside LC Deluxe. I plugged it into my Henriksen Bud 6, and turned the volume up as loud as I could stand.

There is a very faint hum, which dwindles to almost nothing when I hold the guitar at right angles to the face of the amp (which is to say, I point the headstock towards the amp, and hold it just to the right of the amp). I sit about 3 feet in front the face of the amp, in a very small room (my office/studio is 10 x 8, with a 9' ceiling).

When playing at practice volume (which would probably irritate my downstairs neighbors, if they were in the corresponding room), I don't hear the hum at all.

[pcjazz]

I have a Lollar CC in a Tele and a Biltoft CC in a laminate archtop. Both are quiet enough in my practice room, but the hum can be annoyingly loud in certain venues, depending on wiring, lighting, proximity to fridge or ac compressors etc. Even my reissue DeArmond can be noisy in some places. I always carry an EHX Hum Debugger to use when needed.

[RomanS]

I don't think I understand how shielding works.

The business end of the pickup is designed to sense magnetic energy. You don't shield the pickup.

Rather, you shield the wiring and hardware inside the guitar. That is, you try to eliminate noise that is accumulated by the interior wiring and electronics. Seems to me, that for a single coil pickup, it's going to be the pickup itself, not the interior circuitry, that's producing most of the noise. What am I missing?

With a HB pickup, it's different. In that case, the pickup isn't producing much noise, so that the interior circuitry may be contributing a larger part of the overall noise.

This, btw, is consistent with my experience some time back of shielding a HB Les Paul. I used conductive paint, grounded everything etc. I don't recall hearing any real difference.

A guitar pickup picks up two things:

1) The signal caused by the strings - because they are magnetized by the magnetic field caused by the pickup magnets, and when they move (after being plucked) they induce a signal in the coil(s).

2) Noise - caused by the coil(s) acting as antennas for electrical fields.

A humbucker suppresses 2), because the coils are wound in reverse. They pick up the same noise, but the two "noise signals" in the reverse-wound coils are out of phase, so they cancel each other out - the "hum" is "bucked".
Since the two sets of magnets acting on the strings are opposite polarity, the signals ("1)" from above) caused by the vibrating strings are also out of phase - but induced into opposite wound coils - logically, the resulting signals are in phase.
Thats why a humbucker cancels out noise caused by extraneous electric fields, but still picks up string vibration.

With a single coil, there is no second, reverse wound coil - so the noise ("2)") never gets cancelled out, and gets amplified along with the actual signal. That's why the coil should be shielded - so that the "noise" never even gets "into" the coils.

The "noise" doesn't "enter" through the polepieces - those only serve the function of creating a magnetic field that cause the strings to induce a signal into the coil(s).

[rpjazzguitar]

A guitar pickup picks up two things:

1) The signal caused by the strings - because they are magnetized by the magnetic field caused by the pickup magnets, and when they move (after being plucked) they induce a signal in the coil(s).

2) Noise - caused by the coil(s) acting as antennas for electrical fields.

A humbucker suppresses 2), because the coils are wound in reverse. They pick up the same noise, but the two "noise signals" in the reverse-wound coils are out of phase, so they cancel each other out - the "hum" is "bucked".
Since the two sets of magnets acting on the strings are opposite polarity, the signals ("1)" from above) caused by the vibrating strings are also out of phase - but induced into opposite wound coils - logically, the resulting signals are in phase.
Thats why a humbucker cancels out noise caused by extraneous electric fields, but still picks up string vibration.

With a single coil, there is no second, reverse wound coil - so the noise ("2)") never gets cancelled out, and gets amplified along with the actual signal. That's why the coil should be shielded - so that the "noise" never even gets "into" the coils.

The "noise" doesn't "enter" through the polepieces - those only serve the function of creating a magnetic field that cause the strings to induce a signal into the coil(s).

Thanks for the explanation! So a grounded pu cover doesn't affect the magnetic field? Is that true?

[Little Jay]

Thanks for the explanation! So a grounded pu cover doesn't affect the magnetic field? Is that true?

The nickel caps of humbuckers are grounded.

[RomanS]

Thanks for the explanation! So a grounded pu cover doesn't affect the magnetic field? Is that true?

That would depend on the material used for the cover (brass, nickel silver, aluminium).
Also, with some pickup covers changing tone, there's more at work than just altering the magnetic field - added capacitance, and eddy currents (particularly with aluminum covers, like on those Bigsby pickups).

[canadave]

Not sure if this helps but, if your amp has accessible noise gates, this worked like a miracle for me ...

I had this problem as well with a Fishman single coil in hole pickup and tried all sorts of stuff (shielding the back of the pickup, changing cables, eliminating all accessible noise sources, adjusting my physical orientation and that of the amp ... I even tried covering my amp in tin foil). Some of these things improved the situation, but none resolved it to my satisfaction.


Then I stumbled upon this: "Spider heads have built in noise gates. Try holding down the tap button and turning the reverb knob clockwise.", and voila, problem solved. I was just about to ditch the single coil until some random stranger came to my rescue.