How Do I Get Mismatched Coils To Cancel Hum?

[jaguarcat311]

I know it's possible, i have proof in my guitar. a set of lace sensor drop n gains. i've been experimenting with winding my own pickups, but i cant figure out how to achieve hum cancelling with two mismatched coils in series. my friends dad said the inductance had to be the same to cancel hum, but the resistance didnt matter.......i would assume inductance and resistance go hand in hand then......im kinda lost there though... can anyone help me out?

[crafty]

The inductance does not have to be the same. Both coils simply need to have opposite polarity.

[lovekraft]

To expand on what crafty said, any two coils wired out of phase will cancel some hum - the noise will obviously be lowest if they are identical and in close proximity, but even two widely dissimilar coils spaced well apart will cancel whatever noise signal they have in common. Lots of production humbuckers use unmatched coils to get specific tonal colors without any complaints about loss of hum rejection. HTH

[Jester700]

True, but in a similar environment, IME matched coils do reject noise a little better. I know with my guitars a JB does better in this regard than a Steve's Special. I'm not swapping out the SS because I dig the sound, but it would be nice to know if there was a "most important" measurable value for this so it could be taken into account when designing/building.

[JohnH]

this is an interesting one. Opposite polarity is the starting point, but the coils dont have to be identical. I have two Hb,s which when cut to single coils have different resistances (ie different number of turns), of 4k and 6k respectively. They cancell out all hum. It also worls if an SC is in parallel with a series twin-coil with coils out-of-phase with each other. This worls for me, and a 12k out-of-phase Hb camcells out hum with a 4k Sc. It also works on a Strat. Wire your neck and bridge pups in series, all in parallel with the middle (which is RWRP), and one pup cancells hum from two!.

Its magic! The sounds are very close to that of the lower impedance pup, but no hum. Hence these arrangements,are very useful.

Why does it work? My theory is on my site http://au.geocities.com/guitarcircuits

find the page called 'Cancell that hum' and the heading 'Hum cancelling with three active pickups'

Clearly there must be some limits to how different two pups can be and still cancell. I think it needs both pups, or pairs of coils to be wound with similar wire, on a similar core geometry. That way, the more turns you have, the proportionallly more hum it picks up, but also the more impedance the coil has, all in proportion and these two effects compensate.

regards

John

[lovekraft]

They cancell out all hum

Now that's a mighty bold statement, and almost impossible to prove - even saying that they cancel all audible hum is pretty subjective unless you've got an impressive battery of test equipment and a power company transformer to stand next to. That said, I've tried several of the hum-cancelling combinations you recommend, and they all work to varying degrees, although some of the resulting sounds don't appeal much to me (but that's just me). Not knocking you - there's a wealth of useful info on your pages, and we owe you thanks for taking the time to write it all up.

As for whether the most important factor is wire size, coil shape, proximity, resistance, inductance or bobbin color, without either some professional experience in designing and troubleshooting general magnetics in the field (like transformers, or RF inductors - RG, are you out there?) or a large number of tightly controlled experiments for each single variable, the best we can do is make "anecdotally informed" guesses (like CNN, or the White House ). The point I'm trying (and probably failing) to make is that the answers are readily available, and based on proven science that hasn't changed much in a century - any physics majors around here?

[JohnH]

They cancell out all hum

Now that's a mighty bold statement, and almost impossible to prove

Well if you cant make a bold statement on an internet forum, where can you? - we'd all have to hang out in bars where fishermen and golfers congregate!

I know theres always a bit of hum, but I found that my missmatched combos ancell as well as a conventional HB setting on the same guitar, and that got me puzzled.

My main point is that there does seem to be some compensating effects going on. Hum cancelling between mismatched pickups works better than you might think it should. I found this happening and got interested to try to figure out why. So I hope what I did is at least thought provoking, and maybe useful.

cheers

John

[frank falbo]

In my experience, most of the hum cancelling is brought on simply by combining two RW/RP coils. The equality is far less important than the actual combination.

Dimarzio makes pickups with over 4kohms mismatch between coils and they're fine. Remember, make pickups for tone first, and efficiency second. It's agreed that the Steve's Special or Megadrive will have more hum than a matching coil pickup, but it's 100% usable, and quite simply the only way to get that S.S. sound.

If I were making a mismatched humbucker, I'd wrap each coil in shielding tape for good measure. If you minimize the amount of noise that penetrates each coil individually, you'll reduce the amount of hum that needs to be cancelled, right?

[jaguarcat311]

this is an interesting one.  Opposite polarity is the starting point, but the coils dont have to be identical.  I have two Hb,s which when cut to single coils have different resistances (ie different number of turns), of 4k and 6k respectively.  They cancell out all hum.  It also worls if an SC is in parallel with a series twin-coil with coils out-of-phase with each other.  This worls for me, and a 12k out-of-phase Hb camcells out hum with a 4k Sc.  It also works on a Strat.  Wire your neck and bridge pups in series, all in parallel with the middle (which is RWRP), and one pup cancells hum from two!.

Its magic!  The sounds are very close to that of the lower impedance pup, but no hum.  Hence these arrangements,are very useful.

Why does it work?  My theory is on my site  http://au.geocities.com/guitarcircuits

find the page called 'Cancell that hum' and the heading 'Hum cancelling with three active pickups'

Clearly there must be some limits to how different two pups can be and still cancell.  I think it needs both pups, or pairs of coils to be wound with similar wire, on a similar core geometry.  That way, the more turns you have, the proportionallly more hum it picks up, but also the more impedance the coil has, all in proportion and these two effects compensate.

regards

John

←

alright, seriously now, who actaully plays with coils out of phase. im not too big on that sound, yes that cancels the noise in common, but it cancels a lot of the sound in common that i want. so then answer this, how do you make a hum reduced single coil, alone. start there, then you can find out how to make a mismatched humbucker (in phase!) that cancels hum. when you say two coils mismatched in series are quiet, but two matched coils in series are quieter, then the mismatched coils are not hum cancelling. you are avoiding the problem by coming up with solutions that halfway work. im writing a paper on this for school, but mostly i want to know how for my own personal use. i like the sound of my pickups, but if they were silent, that would be an improvement

Edited August 26, 2005 by jaguarcat311

[lovekraft]

alright, seriously now, who actaully plays with coils out of phase.

Anybody who plays any standard humbucker - the coils are physically out of phase, but since the magnetic polarity is reversed on one of the coils, the guitar signal is in phase, while the induced noise is out of phase. That's the whole humbucking principle, in a nutshell. You appear to be somewhat confused about physical and electrical phase relationships - perhaps a bit more research is in order before you write that paper.

how do you make a hum reduced single coil, alone.

Other than shielding it, you don't. It takes a minimum of two coils to make a humbucker.

you are avoiding the problem by coming up with solutions that halfway work.

No, just trying to come up with workable solutions - all suggestions for improvements would be greatly appreciated.

i like the sound of my pickups, but if they were silent, that would be an improvement

I'm going to resist the urge to comment on that statement.

[Jester700]

Remember that even perfectly matched coils will not be perfectly hum cancelling in the real world, because they don't occupy the same space and will thus sense different noise. Given this, if I have a choice between a pup that is "90% of theoretical" in reality based hum cancellation and one that is maybe only 75% but I like the sound better, I might go that direction. DiMarzio has sold a ton of pickups on this principle.

[MerlinTheWizard]

If you're interested by that topic, I think you definitely should take a look at the patents on magnetic pickups. There are tons of them.

That should get you started. (Since it's a link to a patents search, it may take a while to display...)

As for single coil hum-canceling pickups... there are at least two significant manufacturers that make such pickups: Kinman and Lace (sensor). You could argue about their "single coil-ness" (especially the Kinman's) since there is actually a second coil, but it's not supposed to affect the sound. Interesting to look at the patents anyway.

Edited August 26, 2005 by MerlinTheWizard

[frank falbo]

Yeah, I think you're taking the word "cancelling" too literally. Remember: "Sound first, efficiency second." Countless famous tones and albums have been made with inefficient gear. To us, the word "hum-cancelling" simply means that the rejection of hum is taking place. To what degree is far less relevant. But to have two coils on that aren't cancelling hum together usually compounds the effect. So ideally, when possible, you combine coils that will cancel hum with eachother, and let everything else take care of itself. Jester's right, too. If you have an absolute definition of "hum cancelling" then no pickup could ever truly achieve it. One coil would have to exist simultaneously inside the other in a parallel universe (oops, shouldn't have used the word "parallel" - what about a series universe?)

[Jester700]

As for single coil hum-canceling pickups... there are at least two significant manufacturers that make such pickups: Kinman and Lace (sensor). You could argue about their "single coil-ness" (especially the Kinman's) since there is actually a second coil, but it's not supposed to affect the sound. Interesting to look at the patents anyway.

←

Don't forget DiMarzio, the biggest of them all. A few patents under their belt for this as well, and the HS line came out in 1980. I don't like their current legal strategies, but credit where it's due...

[lovekraft]

To us, the word "hum-cancelling" simply means that the rejection of hum is taking place.... to have two coils on that aren't cancelling hum together usually compounds the effect.

Thank you, Frank, for distilling this discussion to its essence - face it, any level of hum cancellation is better than doubling the noise level by adding two coils with their individual noise signals in phase. If it sounds good, and the noise level is low enough to cause no interference with the musicality of the sound, the problem is solved, and further refinement is unnecessary.