Do pickup covers affect tone?

[fett]

Re: Do pickup covers affect tone?

Well, you Einsteins. There is a lot of flapping going on here. [img]/images/graemlins/smile.gif[/img] If you perceive a difference, then there is a difference. And it doesn't make any difference what anyone else sees or hears. So you ask, what difference does it make? To me, none. But, it is an interesting topic.

[dinkyjacksonman]

Re: Do pickup covers affect tone?

I think it does effect the tone.
Also because of the cover you will probably end up placing the pickup just a bit lower position.
Good thing I can think of is it will protect the pickup from sweating and getting older by wear.

[Newc]

Re: Do pickup covers affect tone?

It will only be lower by the thickness of the cover, which is not enough to alter the tone as significantly as removing the cover does.

Makes me wonder if the same rule applies to EMGs [img]/images/graemlins/scratchhead.gif[/img]

Newc

[Ace]

Re: Do pickup covers affect tone?

PICKUP COILS DO NOT VIBRATE. I don't care what your ear is telling you Newc. If you discredit all science because you don't choose to believe it, that's up to you. However, here on Earth we have people who actually dedicate their lives to trying to figure out how everything works together. Maybe you could save everyone some time and just tell us the secrets of the universe that you know to be true. I have made several pickups myself, and I happen to make a decent living working on guitars, and I have met and have the priviledge of watching some of the best guitar techs, repairmen and luthiers on the planet do their job. If you know something we don't, why don't you just revolutionize the guitar industry with your awesome revelation. In the mean time, I guess well just have to believe those stupid scientists.

[RacerX]

Re: Do pickup covers affect tone?

[ QUOTE ]


Pickup height is not hard to match bewteen a covered and uncovered pickup, as the cover is not thick enough that you'd have a distance difference that would affect the pickup's response.

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Sounds like an ASSUMption there, Matt! Kinda like your "coils vibrate" theory. [img]/images/graemlins/tongue.gif[/img]

[Newc]

Re: Do pickup covers affect tone?

Guys, it CANNOT be that hard to grasp. If you don't hear a distinct difference between a covered and an uncovered pickup (same pickup that starts covered, and that cover is removed), then you really need a hearing check.

YES, the copper coils DO vibrate under the influence of the electrical impulses running through them. NO they don't resonate like strings or trem springs, nor do they have the same frequency of oscillation, but there is absolutely no other explanation for ONE pickup having TWO different voices when covered and uncovered. If it's just a case of "hearing it because you want to hear it", then I'd save a bundle on effects like Chorus, Flange, Phaser, and Reverb, because I could just "imagine" they were there.
When I removed the first cover from a pickup, it was not with the thought in mind of "man, this is gonna have a much more open and unmuffled sound", it was "I wonder what it'd sound like if I took the cover off".

Ron - A Gibson USA cover is only 0.02" thick and a Jackson plastic cover is 0.036" thick - neither of those are large enough distances to noticeably affect pickup response.

Newc

[YetAnotherOne]

Re: Do pickup covers affect tone?

The question is pretty simple WRT metal pickup covers: the vibrating strings disturb the static magnetic field generated by the pickup's magnet and as this now non-static magnetic field passes through the conductive pickup cover it generates a currnet within the cover itself. The trick is that this current, like every electric current, has an associated magnetic field. But it's NOT the same field as the one formed by the string/pickup system, it's a new field generated by the induced current in the cover that interferes (not necessarily in a bad way) with the original string/pickup field. Remove the cover, remove this interfering magnetic field, change the tone of your pickup slightly. Ground the cover and you'll change the geometry of the current flow (since it's now flowing out to ground rather than flowing back and forth on the cover with nowhere to go) hence changing the induced interfering magnetic field and in turn changing the sound of the pickup. That one's pretty straightforward.

It's a little tougher to explain why a plastic cover might change the tone but here's a theory for you guys to kick around: The string / air / pickup system looks an awful lot like a capacitor with the string & pickup coils being the conductors (unequally charged because of induced currents) and air being the dielectric material (don't forget that the strings will be in the circuit because they're grounded). Interesting thing is that when the string vibrates, it not only induces a current in the pickup's coils but it will also induce a current in the string itself (a current that flows to ground through the bridge's ground). So what you might have happening is another capacitor being introduced to the RC circuit inherent in the pickup itself. If that's true, you have a very plausible explanation for why a plastic pickup cover would change the tone of a pickup. Namely because plastic is normally an insulator (i.e., it's a dielectric material, a material that doesn't have enough free electrons running around to support conduction of an electrinc current - or inducement of a current) with different properties than the air that it displaced in the string/dielectric/coil capacitor it will change the electrical properties of a the capacitor which will in turn change the electrical properties of the coil's RC circuit which will change the tone of the circuit. Remove the plastic, restore the original dielectric (air), change the tone back. Just a thought.

And yeah, of course coils vibrate. Put your hand on the body of your guitar next time you''ve struck a chord. Feel any vibration? If so, your pickup feels it as well. The effect may be pretty small but those little springs don't perfectly mechanically isolate the coil from the vibration in the rest of the instrument.

Clearly somebody here needs to write a thesis on this stuff. [img]/images/graemlins/popcorn.gif[/img] [img]/images/graemlins/laugh.gif[/img]

[Chuckracer]

Re: Do pickup covers affect tone?

Sounds like you just did!

[YetAnotherOne]

Re: Do pickup covers affect tone?

A friend of mine actually did a survey of the electrical and tonal characteristics of a bunch of Duncan pups as his MS thesis. Duncans because Seymour thought it was a cool idea and sent him tons of free stuff. [img]/images/graemlins/laugh.gif[/img]

[Newc]

Re: Do pickup covers affect tone?

Another point to consider is the natural "what you hear" mix of the covered pickup AND the amplified signal, if your amp is NOT set to a volume that totally drowns out the acoustic tone of the guitar. Plastic and metal covers will reflect the sound of the strings differently, but the bare pickup will reflect the sound the same no matter if it had a metal or a plastic cover, because the bobbins are made of the same material.

Could that be the reason they sound different?

If you've never played (or rarely played) at anything other than stage volume (i.e. drowning out the acoustic tone), would you be able to detect a difference in an uncovered and covered pickup?

Newc

[Grandturk]

Re: Do pickup covers affect tone?

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YES, the copper coils DO vibrate

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To be fair, technically speaking, the whole guitar vibrates in sympathy to the plucked string - some more than others - this is called resonance.

[YetAnotherOne]

Re: Do pickup covers affect tone?

[ QUOTE ]
[ QUOTE ]
YES, the copper coils DO vibrate

[/ QUOTE ]

To be fair, technically speaking, the whole guitar vibrates in sympathy to the plucked string - some more than others - this is called resonance.

[/ QUOTE ]

To be totally fair I think NewC was talking about vibration due to the electrical current passing through the coils, not the mechanical vibration I mentioned. And he's right, there is an electrical component as well. Think about it: electrical current is nothing more than the motion of very large number of charged particles moving through a conductor. The moving particles have some mass and they routinely whack into (that's a techical term) the non-moving CU atoms of the conductor's crystal lattice. Each collision exerts some physical force on the conductor itself though the mass of the charge carriers is so small that the effects aren't readily observable.

I'm with NewC that there's an electrical component to the vibration too but I'd expect the mechanical component to be several (perhaps many) orders of magnitude larger.

[Newc]

Re: Do pickup covers affect tone?

It doesn't really make sense at first to think that a copper wire with electrical current running through it is affected by physical pressure applied to the coil, but the evidence is presented in pickups. A pickup cover that is NOT attracted to a magnet (tin, plastic, whatever) cannot disrupt a magnetic field. Ever placed a magnet on a table and held another underneath it and moved them around? The pickup cover is not thick enough to affect the magnet's influence (field), so it must be compressing the coils themselves, causing either mild electrical shortage (phase cancellation in the outer wraps of the coils) OR promoting/enhancing crosstalk among the outer wraps (and possibly to the inner wraps), which may also be another phase issue.
Once you remove the cover, you relieve that pressure on the wire wraps, or at least ease the tension so there's less pahse cancellation/crosstalk. Remember the soup cans and a string telephone? The tighter the string the better the signal, but if you impede the vibration (current) by pinching the string even slightly, you get a reduction in signal.

Newc

[jackson1]

Re: Do pickup covers affect tone?

This thread has gone too far, if you ask me. It's a mess and i can't clean it up - it would take days.

As an electronic engineer i just want to say to the readers of this thread: you might want to compare certain info disclosed here, with articles and books on the subject found on the net and the library. It's a complex subject and complex matters needs cross checking.

Peace.

[delt]

Re: Do pickup covers affect tone?

> so it must be compressing the coils themselves, causing either mild electrical
> shortage (phase cancellation in the outer wraps of the coils) OR
> promoting/enhancing crosstalk among the outer wraps (and possibly to the inner wraps)

This seems like the most logical theory. Someone should try cutting out the top of a cover and trying just the top and just the frame, see how both affect the tone.