What does the distance between a pickup and strings do for the sound? Should active and passive pickups be treated differently?
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4 Answers
The distance from the pickup to the strings determines - in simple terms - the strength of the magnetic field acting on the strings. Since a standard magnetic pickup (active or passive) is an electromagnetic transducer, the output voltage is generated when a string vibrates in a magnetic field.
So far so good, what of the pickup height? The stronger the magnetic field around the string - achieved by bringing the magnetic polepieces closer - the higher the output generated. However, in this world you never get something for nothing: a stronger magnetic field will dampen the vibration of the strings, decreasing sustain.
Thus, finding the right pickup height is a matter of compromise and experimentation. You'll probably want the pickups high enough to generate a healthy signal, but low enough to allow the strings to vibrate freely. The exact height will depend on the strength of the magnets in the pickup.
Active pickups simply incorporate additional preamplification circuitry, so the principle is the same as for passive pickups.
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+1 good answer. You covered pretty much everything, so nothing more to say 'bout this topic. Well, maybe that typically a humbucker has a higher effect on the strings than a single-coil. (obviously) And that the amount of pick-ups is also important, which is one of the reasons why guitars with just one pick-up in the bridge-position are getting more popular "these days". The question is, what has more impact on the strings, pole-piece magnets or blade-magnets? I've always been wondering about that...– AnonymousMay 16, 2011 at 7:11
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The last question would probably involve examining the magnetic field generated by each - possibly interesting from a Physics standpoint, but I'm not sure whether very practical for us guitarists, especially since height adjustments will generally be determined through experiment. As to the popularity of single-pickup guitars, I've always thought it was more a question of simplicity (especially if the controls consist of a single volume pot), than technical considerations.– user321May 16, 2011 at 7:25
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Well, my last question isn't a live-depending-on question, but I think that it's a rather interesting question. And about single-pick-up setups: of course simplicity is important but it has an effect on the sustain, too. My work-in-progress guitar (an old LP-style guitar) currently is stripped down to the minimum: bridge-HB > volume-poti > output-jack. And it has a noticable amount of sustain more compared to the 2 humbucker setup. (It's lighter, too obviously)– AnonymousMay 16, 2011 at 8:56
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The string thickness also has an impact in this regard. Thicker strings => more intertia => more sustain. This can let you elevate your PUs to get even more sustain, if need be. Oct 14, 2014 at 8:12
There's one more important thing the answers so far haven't mentioned: a pickup's output signal doesn't follow the string movement simply in a linear fashion, but in a rather complex relation depending on inhomogenity of the magnetic field, coil geometry etc., and the closer you get the more nonlinear. The result is somewhat similar to a gentle but very asymmetric tube overdrive: you add some (predominantly even) overtones, and "straight-smear" inharmonicities. The result (in particular in connection with the increased inharmonicity through magnetic damping) means that a pickup close to the strings can sound something from agressive-growl to shrill-clang.
Apart from that, these nonlinearities behave quite unlike when you distort the entire guitar signal: there's no intermodulation between different strings (what makes powerchords fat and jazz chords muddy), nor dynamic compression that most distortion has as side-effect. So adjusting a pickup closer sounds very different from boosting a tube input gain to the same final level: more "direct", "fast", "wide", "hard", whereas a pickup further away with higher gain sounds rather mellow, sustained, "smooth", "bound".
answered Oct 13, 2014 at 22:03
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I saw a YouTube video of someone removing one set of pole pieces from a humbucker and getting a sound much closer to that of a single-coil pickup while retaining the noise-cancellation advantages. I would expect that what makes humbuckers sound different is the fact that the field lines from one set of pole pieces are bent toward the other, thus creating a stronger magnetic-field gradient and increasing the non-linearity of the response; I would further expect that an empty coil placed next to a single-coil pickup would naturally receive an anti-phase magnetic signal...– supercatNov 22, 2014 at 18:08
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...and thus wiring such a coil in series with the primary coil would yield the noise cancellation advantages of a humbucker without the distortion. I wonder why I've not seen guitars do that? Also, I would think that if a guitar used magnetized pole pieces, having "C"-shaped pieces of metal which touch the magnet in the middle (forming an "E") and wrap around the sides would improve gain; do you know if that's what some of the more exotic pickups are doing?– supercatNov 22, 2014 at 18:12
As mentioned, having the pup close to the strings gives a hot signal and increases the magnetic dampening, but there is also an effect on tone as well. IIRC, having the pickup near the strings is more trebley and having them lower is more middy. (But it may be the other way around). Additionally, with most humbuckers having at least 1 coil with adjustable pole pieces, you can set the pup low and jack up the poles to get a bit of a blend, or set it high with the poles screwed down as far as poss. These sort of settings are far more subtle than the type of pup and moving between bridge and neck positions, so you'll need to experiment to find out what works for you, if you can even tell what's going on.
a good place to start as to string distance from string to pick-up pole are...
While fretting a note on your gits highest fret on the High E string the distance from the string to pick-up pole should be the thickness of a "DIME" for a Neck Pick-up
and the thickness of a "Nickel" for a Bridge Pick-up
REPEAT: on your Low E string
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3This doesn't answer the question, and is in fact not correct. All players have different preferences for string height.– Doktor Mayhem ♦Feb 15, 2013 at 9:34