What do guitar pickups pick up?

The pickups with two pole pieces per string are "hum-bucker" pickups - essentially two pickups wired out of phase with the magnets in one reversed, this cancels out magnetic hum fields while leaving the signal in phase.

As far as motion.. good question, seems to me that motion towards and away from the pickup would result in a fundamental and motion parallel to the pickup pole pieces would result in a 2nd harmonic component if right over the pole piece. Some pickups use just a single continuous "blade" pole piece, hard to see how that works at all for parallel motion but they sound ok. Also consider that the strings vibrate with different mode shapes so where the pickup is placed makes a big difference in tone. I like the humbucking type pickups better because they sample in two places giving a more balanced output.

- Terry

Am 02.06.2016 um 17:19 schrieb Tim Wescott:

If you can read German:

regards, Gerhard

That reminds me of the old black Springer-Verlag books, Band 1, Band 2, ...

Den torsdag den 2. juni 2016 kl. 17.19.22 UTC+2 skrev Tim Wescott:

afaiu it is because if the magnets are too strong the field starts to dampen the vibration of the strings so it doesn't "sound right"

as others mentioned the dual pole piece is a humbucker

-Lasse

Bass pickups have two pole pieces that straddle the string, not arranged along it like Humbuckers. Google "P-type" and "J-type" pickups.

Thanks. I'll give that a try. Sometimes I can read technical German -- well, I can at least pick my way through and get the general gist of things. With effort and a dictionary I do OK.

Ditto French, which is really embarrassing because my knowledge of French is basically composed of two factors: one, I've been taught German, and after you take German out of English you've got a whole lot of French, and (I blush) watching Pepe le Pew cartoons as a child.

...SOME bass pickups. Some guitar pickups also have two poles per string. There are bass pickups in all flavors.

try "single coil bass pickup" "blade bass pickup" "soapbar bass pickup" and of course "piezo bass pickup"

If you'd like to dive down a rabbit hole that may have a _very_ high myth to engineering ratio:

If Peavey hasn't totally borked their site they had some white papers that were only a little bit pushy to "their stuff." Seems to still be there. Might be too basic for your taste, but not 1200 pages auf Deutsch.

General impression - most folks that make money at it would prefer that it remains as mysterious as possible. ;^) There is both lack of good detail and the distinct possibility of red herring strewing in what is out there.

As for the motion-sensing, it's pretty much any string motion that crosses magnetic field lines (like any other generator, albeit it's a wickedly wimpy one), so "both" is your likely answer.

try asking at rec.audio.pro

Mark

The combination of the guitar string, permanent magnet, and coil form a magnetic circuit.

As the string moves up and down, the reluctance of the magnetic circuit changes, because reluctance is directly proportional to cross-sectional area of the magnetic circuit, and the cross sectional area depends on the position of the string above the coil. As magneto-motive force is directly proportional to reluctance, and the quiescent magnetic flux density is fixed by whatever the H field of the bar magnet is, an current is induced in the coil as the reluctance of the magnetic circuit varies above and below the quiescenet point.

Stupid question: Do they put more turns (or otherwise increase sensitivity) on those pickups underneath the smaller strings? Do they make magnetically loaded strings?

George H.

I'd guess so..I'm a guitarist but not a pickup designer. As you might imagine there's every different type of pickup under the sun with all sorts of patented technology to appeal to someone's tastes...more turns gives "hotter" output in general, and you can select according to whether you want that "vintage" or a more "modern" hotter output sound.

They also make active pickups that are battery-powered and have an internal amplifier to lower the output impedance. They also make "sustainer" pickups that have an active feedback mechanism that turns the coil into a transducer for driving the string, so you can pluck a note and flip a switch and it will just ring forever as if you were bowing a violin.

They make "modeling" pickups with an internal DSP that samples the pickup output and runs it through whatever algorithm, so you can spin a dial and your guitar can sound like a Strat, or a Tele, or a Gibson, or a 12-string acoustic or sitar or whatever you desire at the moment.

All sorts of stuff.

In addition, usually the pickups are mounted in an "angled" way so that the lighter strings are closer to the coils than the heavier ones.

I don't know about magnetically-loaded strings...I know people with nickel allergies can buy strings that are silver or gold plated. They're naturally really expensive, I think a 6 string pack of gold strings for an electric was around $30 last I looked.

They supposedly to have a really good sound, though...but that just might be buyer's rationalization.

Not interested in myth at all, at least at the moment. Just curious about what's really going on.

Don't think it's that simple -- the string will be pulling magnetic field lines with it, more like. I'm trying to figure out why you would have a pickup that's going to have the best chance of properly registering motion orthogonal to what you induce when you strum the damned thing.

the pickup has a height adjustment on each side and different heights of the pole pieces so they are at different distances from the strings

there is only one coil

-Lasse

Usually the coils are around the whole group of pole-pieces, though there are exceptions - but "coil per string" pickups are rare outside of single-string pickups, which are themselves a rarity.

Distance to the string is adjustable - the whole pickup is "sprung" in its mounting hole, and the mount screws can be adjusted to alter the level and angle of the face. Some pole pieces are also individually screw-adjustable for height. There is a tradeoff of output increasing as it gets closer, and string pull/damping from the magnet also increasing as it gets closer.

Likewise, more turns to make a hotter pickup usually goes with thinner wire, so the source impedance goes up, too. This is a physical space constraint for "standard" pickup sizes, which are generally pretty full of wire, whatever the number of turns.

Den torsdag den 2. juni 2016 kl. 23.35.17 UTC+2 skrev Ecnerwal:

it also changes the inductance and resonant frequency, many variables and it seems everyone just keep doing what has always been done since that is what people want and expect

add to that some the audiophile things like, the randomness of hand wound sound better than the regularity of machine wound, the materials should be the old school stuff form way back when etc.

-Lasse

I guess that's me. I was a violinist, am a not-very-good guitarist, have built three guitars, and wound my own pickups using a machine I made myself. And although I have little formal training in electronics (some 3rd-year EE subjects), have very good physical intuition and a fair amount of theory.

No, but I can answer a lot of the questions, and even suggest a physical basis for some of the apparently mystical hoo-ha. Sorry, but I can't do the math for you though.

I toyed with the idea of writing seven separate responses, but I'll just answer the seven messages all in one omnibus.

I suspect that the Alnico magnets, being weaker, have wider more circular field lines (more field leaves the magnet by the side door), whereas stronger magnets = higher permitivity are more elliptical. Being more circular would admit fewer high harmonics for a sweeter sound, so there may be truth in the myth.

All guitar strings move in both dimensions, and precess from more-horizontal to more-vertical and back. The H and V components are of phase (spiral oscillation), and even slightly different effective frequencies, depending on the compliance and energy absorption at the end points. Good players get their particular "sound" by making use of all this. The string can be plucked across or upwards, and with wider strings, they roll off the finger to start with a spiral.

Plucking close to the bridge provides more high harmonics, and of course, players use that effect extensively. Likewise, the bridge pickup gets less fundamental, more harmonics than the neck pickup. Guitars have been made with pickups that slide up and down, even during playing, to stop at different nodal or anti-nodal points.

Strings also suffer length-ways oscillations, which you hear when the hand is slid along them, but it's an ugly screech made up of non-harmonic (Bessel) components.

Because of the limited flexibility of the string material at the fixed ends, the Mersenne equation doesn't properly describe the motion. Instead you get a bending column effect, which has the tendency to reduce the effective length more at higher frequencies. So the first harmonic is slightly more than an octave, and higher harmonics are progressively higher. This is the source of "inharmonicity" which is why e.g. piano's use "stretch tuning" where the high notes are usually a couple of semitones sharp compared to the low ones. Some players like more "stretch" than others, though few of them know why.

George H asked: > Do they put more turns... underneath smaller strings

No, they adjust the pickup or pole pieces closer to the string.

Lasse commented: > if the magnets are too strong the field starts to dampen > the vibration

It's worse than that, it induces a nodal point which kills specific harmonics and enhances others.

Dual-pole pickups (more commonly associated with Gibson) add the signal from two parts of the string a short distance apart, which softens some high harmonics, which partly explains why they have a sweeter less piercing sound. Fender-style pickups have only a single pole and are more associated with screaming soloists. There are still humbucking arrangements but those aren't traditional.

bitrex mentioned silver and gold strings:

Larger strings are over-wound; a solid wire of the right weight would be too rigid, so you get stronger "column" effects at the ends, and more damping of higher harmonics. The problem is that as the skin acids corrode the string, the windings become loose on the core. Di Addario and others counter this with a hexagonal core, so the windings are spring-loaded against the corners, and those last longer. You can also get strings that have a titanium core, though I think the preferred winding is still phosphor-bronze. But the effect of loose windings is energy loss especially at high frequencies, and the strings sound dead. I suspect that silver and gold are used (a) to reduce corrosion and (b) to pamper the ego of the buyer. Pampered egos make better music, so why not?

Lasse mentioned the effect of wire size.

For the same winding volume, a reduction in wire diameter gets you more turns by the square of the reduction. More turns gets you more inductance by the square of the number of turns. So the inductance goes as the inverse fourth power of the diameter. Resistance also; more turns, smaller cross-section. There is a lot of distributed inter-winding capacitance too, and I'm not sure the exact power here; perhaps 2nd or 3rd power approximately? Perhaps someone here can answer that. The capacitance seems to be affected by whether the coil is close-wound or scramble wound, which explains the preference for hand-winding.

Anyhow, the upshot is that pickups tend to have a very low-Q resonance between 2 and 5KHz, and they're all different.

The modern powered pickups often use many fewer turns feeding a low-noise low-level pre-amp in the pickup itself; any sound shaping that was lost from the winding changes is added by analog filters.

Finally, there's no good reason why the windings have to run around the magnets. The pickups I made use a hard ferrite blade or a row of traditional magnets, magnetised from top to bottom, but instead of the windings going around the outside in the horizontal plane, I make two windings in the vertical plane, one each side of the magnets. It's actually *more* effective at capturing delta-B, and you can wind both coils at the same time for a full humbucking pickup, without having a broad or dual-row center. You get more high harmonics than a Gibson-style humbucker, and more hum-bucking than a Fender style, and more output than either with no increase in string drag (same magnet strength).

I thought about patenting it, but it's quite close to a design that Gibson used (and patented, now expired) on the EB-1, -2 and -3 basses. Their construction was terrible, huge and clunky compared to mine, and they weren't very successful. But there's still a business for someone who wants to manufacture my design.

Clifford Heath.

I'll add that in bass strings there are nylon tapewound strings, that are overwrapped with a nylon layer, which keeps corrosion and gunk from the actual string, and also alters the tone (in a way I happen to like for bass.) There are also newer types of coated strings that try to sound more like a plain roundwound string.