Wiring 2 single coils for hum cancellation

Paul Brainard · Post by **Paul Brainard** » 1 May 2003 3:34 pm

Has anyone tried wiring the two single-coil pickups on a double-neck guitar so they are in reverse of each other when the selector switch is in the middle & both are engaged? Will this create a hum-cancelling circuit or is it not that simple?

Donny Hinson · Post by **Donny Hinson** » 1 May 2003 4:22 pm

Uhhhh...the pickups have to be on the same neck! Some humbucker designs are actually two separate pickups wired together, but they must be on the same neck, and they must be close to each other. I think the balance becomes a problem when they're separated by more than an inch or so, due to the nodal points of the string.

Good question, though!

Paul Brainard · Post by **Paul Brainard** » 1 May 2003 5:58 pm

Well, do they really have to be? I would think they'd each pick up the same hum on either neck. As long as they're wired 180 degrees out of phase, which is the same as reversed polarity (isn't it?), then it should cancel out when you have them both engaged. I personally don't ever use the middle switch position, but I'm thinking this might be a useful option to have in a noisy environment. Not sure how it will sound but I guess it would be easy enough to give it a try.

Earnest Bovine · Post by **Earnest Bovine** » 1 May 2003 7:36 pm

Yes, that should cancel most of the hum. If the source of the hum is closer to one pickup than to the other, then one signal will be stronger and they won't cancel exactly.
I think my double neck worked that way (less hum with both pickups on).

The signals are of opposite polarity, not out of phase.

Earnest Bovine · Post by **Earnest Bovine** » 1 May 2003 7:51 pm

"Out of phase" means half a wavelength away. It is impossible to say that a complex audio signal has any one wavelength, because, unless it is just a pure boring unchanging sine wave, it has many wavelengths.
Wavelength of electromagnetic radiation at a typical audio frequency of 1000 Hz would be c/f = 3*10^5 meters, so to get out of phase at at this frequency, you would have to go from Nacogdches to Natchitoches.

jim milewski · Post by **jim milewski** » 2 May 2003 5:04 am

Nacogdches to Natchitoches...that would also change the string spacing, I bet someone is humming a tune in Nacogdches right now, and damn, you're right, I can't hear him

Michael Johnstone · Post by **Michael Johnstone** » 2 May 2003 9:04 am

Aren't the pickups on Stringmasters wired like that? Aren't they really just humbuckers with the reverse wound coils seperated by 2 inches? And I thought I heard of a single coil pickup Bill Lawrence was offering briefly that had a 2nd reverse wound coil wired to it but mounted seperately somewhere else on the guitar.
-MJ-

William Peters · Post by **William Peters** » 2 May 2003 12:40 pm

Not only are the 2 coils reversed on a humbucker, but the magnets also have to be reversed. That is, all the North poles up on one coil, and all the South poles up on the other. If you take two single coil pickups, mount them side by side, and wire them up out of phase, the string signal will also be canceled out along with the hum UNLESS the magnets are reversed on one of the pickups.

Bill

Ricky Davis · Post by **Ricky Davis** » 2 May 2003 1:41 pm

William speaks the truth as was explained to me by some authorities.
Ricky

Paul Brainard · Post by **Paul Brainard** » 2 May 2003 1:58 pm

So you'd have to have one of the pickups built for the purpose of wiring them like this. . .

I had talked briefly with Jerry Wallace about the concept of adding a second hum-cancelling coil but didn't know it had been tried - I wonder how well it worked for Bill Lawrence?

How 'bout this idea - if EMI or whatever electrical hum we hear is an environmental factor, in the airwaves or electrical circuit, it seems like it should be possible to add an inverse/cancelling signal to the environment & clean it up?? I have done this in the studio with combination sampler/signal generator with some success, and ProTools has a plug-in ("Ray-Gun") that does the same kind of thing, but wouldn't it be handy to have a gadget you could plug into your rig (signal path or power supply?) that would read the background noise, invert it, and add that in to clean things up? I suppose it probably already exists. The drawback is that you end up losing those frequencies from your tone as well.

The best solution would be a pickup that you could switch from single-coil to humbucker and that would sound good in both configurations (I've tried the George L 5-1, but it wasn't for me. . .)

Donny Hinson · Post by **Donny Hinson** » 2 May 2003 4:05 pm

Contrary to popular opinion, even guitars with "humbuckers" will hum a little! Also, be advised that any preamp (steel-driver), or amplified volume pedal, can make the hum problem worse. Notch filters are available if you have a serious problem, and they will put the offending 60hz or 120hz signal down by about 30 db, more than enough to satisfy most people.

A lot of hum problems are also caused by cheap cords, or poorly-shielded volume pedals. Humbucker pickups will do nothing to alleviate those.

Michael Johnstone · Post by **Michael Johnstone** » 3 May 2003 9:40 am

I had a guy tell me recently that putting a 100 watt 1 amp diode across the output of a single coil pickup would get rid of hum. Anybody ever tried that? -MJ-

Earnest Bovine · Post by **Earnest Bovine** » 3 May 2003 10:30 am

<SMALL>putting a 100 watt 1 amp diode across the output of a single coil pickup would get rid of hum</SMALL>

What could possibly be the theory behind that?
And what is a "100 watt" diode? The only ratings I can imagine for a diode are the max current downstream before it fries, and the voltage that will break it down upstream.

J Fletcher · Post by **J Fletcher** » 3 May 2003 2:41 pm

I seem to remember that Alembic (?) guitars had a dummy coil in them just for the purpose of reducing single coil hum. Don't know how it was wired, as these guitars usually had active electronics, but I'd guess it was reverse polarity to the other pickups, and then the output of this coil was blended in to the other pickups' signal until the hum was minimized as much as possible. Don't know if there were any magnets with this dummy coil....Jerry

Michael Johnstone · Post by **Michael Johnstone** » 3 May 2003 4:46 pm

I haven't really thought it thru on a theoretical level - I'm just repeating what John Fry told me and he generally knows what he's talking about.I wrote down what he said and figured I'd try it when I get around to it. I've tried an inline hi-pass filter and it just destroys the tone of a single coil but I carry it in my pack-a-seat for those gigs where 50% of what's coming out of your amp is hum. -MJ-

Earnest Bovine · Post by **Earnest Bovine** » 3 May 2003 4:57 pm

If the hum is 60 Hz and multiples of 60 Hz, then it seems to me that you could get rid of hum by delaying the signal exactly half a cycle (1/120 second) and inverting it, then combining that with the original signal at exactly the same amplitude.
Of course you would be in trouble if you wanted to hear a multiple of 60 Hz, so avoid playing those notes!

Bob Hoffnar · Post by **Bob Hoffnar** » 4 May 2003 4:28 am

You can get rid of pickup hum on single coils by putting both pickups on on a D10 if the pickups are wired right.It does reduce output though.

Williams steels are built like that.

I had an old Alembic bass that used a dummy pickup inside the body cavity that did the same thing.

Bob

Jim Bob Sedgwick · Post by **Jim Bob Sedgwick** » 4 May 2003 11:59 am

Bob I own a Williams. I have had humbuck pickups and single coils both on the guitar. There's only about a 10% difference in hum between them. I prefer the single coil myself. I have done quite a bit of recording with the single coils and never had a complaint from any of the engineers I have worked with.