How Do Humbuckers Work?

Discussion in 'Just Pickups' started by Chanan, Jan 7, 2021.

  1. Chanan

    Chanan Tele-Meister

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    I must be missing something here, I just can’t quite wrap my head around it...

    If a humbucker consists of two coils with opposing polarity, shouldn’t they just phase cancel each other entirely? Or at the very least sound ‘out of phase’? Usually that sound is associated with being thin or nasally, but humbuckers seem to be the opposite, with a lot more bottom end than single coils.

    Does the humbucker design utilize phase cancellation in order to get rid of the hum? Can certain cycles or frequencies be isolated for phase cancellation, while the rest of the spectrum is unaffected? Is there something more nuanced to the humbucker design - beyond two opposite wound single coils - that I’m missing?
     
  2. beanluc

    beanluc Tele-Afflicted

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    The magnets are also reversed, so, yes, you're right, ambient RF radiation which is picked up by the two coils is phase-canceled. But because of the reverse-polarity magnets in the two coils, the string vibration induces the signal in the two coils in the same phase.
     
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  3. strat a various

    strat a various Friend of Leo's

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    Correct me if I'm wrong, reverse phase and reverse polarity are not the same thing.
     
  4. beanluc

    beanluc Tele-Afflicted

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    You're not wrong. The magnets polarity and the pickup wind directions are reversed from each other so that the unwanted signals are out of phase between the two coils and the wanted signals are in phase between the two coils.

    I mean, it's a good thing they're not the same thing or else you'd have to choose between noise with signal or no signal and no noise.
     
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  5. strat a various

    strat a various Friend of Leo's

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    BUT, out of phase will cancel hum ... I have a Vox bass with single coils that is stubbornly noisy unless the switch is set for both pickups. (Which I reversed the wire to achieve hum cancelling ... I guess I also reversed the polarity?) The 2 and 4 position on a 5-way Strat pickup cancels hum, right?
     
  6. beanluc

    beanluc Tele-Afflicted

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    Probably not - a matched pair of pickups already comes with the correct magnet orientation to support hum canceling without making the signal out of phase.
     
  7. strat a various

    strat a various Friend of Leo's

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    I think when they built this bass (Asian matsumoku body) they just had a bin of pickups, and threw two on each instrument.
     
  8. beanluc

    beanluc Tele-Afflicted

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    Yeah, I was answering a question you didn't ask, sorry.

    So if reversing the wire eliminated the hum, it also must have put the signal out of phase. Not sure what that sounds like on a bass, but on a guitar it's pretty noticeable.

    Strat positions 2 and 4 are hum canceling but not phase reversed, because the middle pickup is reverse wind, reverse polarity.
     
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  9. strat a various

    strat a various Friend of Leo's

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    My main Strat has a three position switch, but when I accidentally hit 2 or 4 on my backup, a Bullet Strat, it sure sounds out of phase.

    On that Bass, the out of polarity(?) sound is quieter and less Bassy, but with the right amp, it sounds very "acoustic" and on a short scale full-hollowbody (really), it works.
     
  10. AJBaker

    AJBaker Friend of Leo's

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    The result is the same though.

    Take two identical single coil pickups (same polarity, same wind direction). If you play them together, they are in phase, but not hum cancelling.

    You have two ways of putting them out of phase: reversing the wind direction, or inverting the polarity. Both have the exact same effect of putting the pickups out of phase, and the sound of both pickups together would then be thin and nasal, but the hum is gone.

    In a next step, imagine putting it out of phase AGAIN. I.e, if you reversed the coil direction on the second pickup, now ALSO reverse its magnetic polarity. The two pickups are now like double out of phase, which ends up being in phase again, but with the effect of cancelling the hum.
     
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  11. strat a various

    strat a various Friend of Leo's

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    So, when I switch the wiring (and get a nasal tone), I've reversed the phase, but not the polarity (pick ups are identical, I'm presuming), so polarity shouldn't be changed, right?
     
  12. AJBaker

    AJBaker Friend of Leo's

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    That's right.
     
  13. strat a various

    strat a various Friend of Leo's

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    Cool.
     
  14. moosie

    moosie Doctor of Teleocity Silver Supporter

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    What you're missing is the difference between HUM cancellation, and SIGNAL cancellation.

    The windings and the magnets work together to carry the guitar signal. The windings, all on their own, however, also pick up RF interference (aka hum).

    Magnet orientation only affects the signal phase.
    Wind direction affects both phases, signal and hum.

    To change signal phase, change EITHER the magnet orientation, OR the wind direction. Changing both changes it twice, and you're back where you started.

    That's the key. If the coils are already in phase (talking about the signal here), but they're noisy, change BOTH. Changing the wind cancels hum, and puts the signal OOP. But changing the magnet un-does that, and brings the signal back into phase. Noise-free.

    RWRP is just this, in phase, hum cancelling. Start with two identical coils, and RW (change wind direction), RP (change the magnets) on just one pickup. The term is applied to single coil pairs, but it's also true of every humbucker, too. You can of course change the coil direction on a humbucker, if you have access to the coils separately (4-wire). But it's not so simple to change the magnets.
     
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  15. DougM

    DougM Poster Extraordinaire

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    What no one is addressing here is that the 2 and 4 positions on a Strat sound the way they do because there's always some phase cancellation when two pickups are on together, whether they're RWRP from each other or not. The closer together the two are, the higher the frequencies that are cancelled. That's why a HB has less high end than a single coil, because the coils are closer together, and so the phase cancellation occurs at higher frequencies.
     
    Last edited: Jan 13, 2021
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  16. smoothrecluse

    smoothrecluse Tele-Afflicted Silver Supporter

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  17. rigatele

    rigatele Tele-Afflicted

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    Not quite. When they are separated by any significant distance (i.e. not like a HB), there is a mixture of in-phase and out-of-phase signals, where the out-of-phase signals are suppressed. Since there are nearly as many in-phase as out-of-phase cases, the effect is to modify, not suppress the high frequencies. That is because it causes some of the highs to be suppressed, but others enhanced. The reason a HB always suppresses some highs, is that the pole separation places the effect at the very high end of the audible spectrum. In fact, it does enhance some highs but at the 3rd overtone vs. the 2nd overtone (of the aperture length not the string length) which cancels at the poles. However the string itself doesn't produce enough energy at that higher frequency to be audible. Although it is a sensible and proven fact, the more muted sound of a typical HB is more due to the much higher inductance than to the pole spacing aperture.

    In the Strat case, and in other cases also, the tone of parallel connected pickups (such as position 2, 4) is different partly because it is simply sampling different parts of the string, and partly because connecting them in that fashion, cuts the inductance in half and doubles the capacitance, thus altering the electrical characteristics that contribute to tone.
     
    Last edited: Jan 14, 2021
  18. Dan German

    Dan German Doctor of Teleocity

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    Humbuckers are quite simple: the vibration of the string creates an electrical current in both coils; the north coil removes the twang, and the south coil adds the mud. There ya go.
     
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  19. Fuelish

    Fuelish Tele-Afflicted

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    I tend to not dwell on it... humbuckers buck hum, single coils hum... grew up with 60 cycle etc hum, so it doesn’t bother me in the least... the DeArmond gold foils on my ‘64 Harmony make me feel warm and fuzzy after all these years ... nostalgia is a helluva drug
     
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