What affect do added pickup covers have on tone?

[Jr_vw2]

I have a dimarzio x2n pickup that I really like. And I'm going to try in my sg. If I find that I like that PU in that guitar I would really like to put a chrome cover on it. How will the added cover affect the tone? Should it be potted to keep it from becoming microphonic?

On an added note has anyone tried an x2n in a SG? I had it in an old charvel model 1 and loved that pickup.

 

[Karan D. Taktawala]

Re: What affect do added pickup covers have on tone?

Say the same thing with varying degrees of contact with hand over mouth.

Between Raw nickel which is = placed farthest, least effect
and Brass which is = placed closest, max effect

But in any case it will muffle your tone a bit


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[SirJackdeFuzz]

Re: What affect do added pickup covers have on tone?

Say the same thing with varying degrees of contact with hand over mouth.

Between Raw nickel which is = placed farthest, least effect
and Brass which is = placed closest, max effect

But in any case it will muffle your tone a bit


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. . . and plastic vs. metal for P90's ?

 

[Gtrjunior]

Re: What affect do added pickup covers have on tone?

Isn’t the X2N a rail pickup?
Can you get a cover that will properly expose the rail?

 

[Chistopher]

Re: What affect do added pickup covers have on tone?

Say the same thing with varying degrees of contact with hand over mouth.

That is a completely different principle at play than what happens with a pickup.

And raw nickel does not have a drastic enough effect to be worth it over the polished stuff. If you want transparency, the important thing to go for is nickel silver, not just plain nickel.

 

[DavidRavenMoon]

Re: What affect do added pickup covers have on tone?

That is a completely different principle at play than what happens with a pickup.

And raw nickel does not have a drastic enough effect to be worth it over the polished stuff. If you want transparency, the important thing to go for is nickel silver, not just plain nickel.

Nickel covers are nickel silver. None of them are nickel. Nickel is ferromagnetic, so you wouldn’t want pure nickel for a pickup cover.

Nickel silver is a form of white brass. The usual formulation is 60% copper, 20% nickel and 20% zinc.

Chrome plated covers often have an additional layer of copper. Either way the issue is the more conductive the cover is, the more eddy currents that will form. It’s the eddy currents that change the tone. The effect is to lower and flatten the resonant peak. The high frequency response of the pickup starts to drop off right after the resonant peak.

Brass covers are much worse. Aluminum would be more so.

And of course plastic has no effect.

Seth Lover wanted non magnetic stainless steel covers. EMG uses that on their metal covered pickups.

If you break up the surface area you reduce eddy currents. This is why the Filter’tron has the H cutout.


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[Artie]

Re: What affect do added pickup covers have on tone?

I debated with myself whether to comment here, but then again, it is a forum for discussion. And I do mean my comments in a discussive, rather than dismissive, tone.

I have hard time accepting the tonal impact, if any, of eddy currents in a guitar pickup. Here's why I lean this way. Eddy currents first became known to be a problem in power transformers. Because of the amount of current that flows in a PT, eddy currents can be of considerable magnitude. They can cause considerable power to be wasted in the core of the transformer. This also generates heat which further degrades the efficiency of the transformer. But in a guitar pickup, which is a tiny AC generator, the current is microscopic. There's a couple different measurements that I made before I retired from a Navy Cal Lab. One, was just to plug a guitar straight into a 'scope, (which just happens to have a 1 meg input impedance), and see what the voltage was when doing normal strumming and picking. We had a really nice digital storage o'scope that allowed me to retain the "envelope" of the signal through repeated strumming. A typical voltage, with a humbucker, would be around 350 mv's. Striking the strings hard would get an instantaneous peak around 1 volt pk-to-pk. Its duration was only one or two cycles, then quickly degraded to the millivolt level. A typical guitar pickup load, of a 500k volume pot going into a 1 meg amp, would be around 333k. At 350 mv's, that equates to around 1 microamp. That's .000001 amp. The electromagnetic field that would develop around that would be even smaller. And then that field would have to couple with the cover through a distance of air.

The next measurement I tried to make was to use a very expensive, very precision, picoammeter to actually measure the current in the cover of a humbucker while a friend played some chords vigorously. This is a meter with 9 or 10 digits of resolution in the picoamp range. No matter where I touched the leads to the cover, we were unable to measure anything. And remember, this is in a temperature and humidity controlled cal lab with all lab grade calibrated equipment.

That then leaves "listening" tests to determine if there's any tonal impact. The problem I have with that, is simply that to have eddy currents, you must also have metal, in the vicinity of the pickup. But that's going to alter, or reshape, the pickups own magnetic field. We know that adjusting pole pieces, or even trimming the pole screws on the bottom, impacts the tone. How would one know if what they're hearing is caused by eddy currents, or just the presence of the metal?

Anyway, that's my 2-cents worth on eddy currents as they apply to guitar pickups. I'd love to be proved wrong, but I'm not sure how that would happen. But I'll remain open minded and all ears.

Artie

If you break up the surface area you reduce eddy currents. This is why the Filter’tron has the H cutout.

I can't help but wonder, if someone were to solder a jumper across that gap, would they be able to actually hear a difference? :scratchch

 

[freefrog]

Re: What affect do added pickup covers have on tone?

Artie, here is something that you might find interesting:

http://kenwillmott.com/blog/wp-content/uploads/2016/11/Pickup_Cover_Geometry.pdf

FWIW.

I have a dimarzio x2n pickup that I really like. And I'm going to try in my sg. If I find that I like that PU in that guitar I would really like to put a chrome cover on it. How will the added cover affect the tone? Should it be potted to keep it from becoming microphonic?

IME, chrome covers tend to increase the inductance (as measured with a lab meter) while other "non transparent" covers decrease it... but the actual influence of a cover is hard to predict IMHO, because covers are not exactly created equal.

Foucault currents a.k.a. eddy currents are not something that I'll discuss here (too busy for that). Let's just say that IME, when their effect on a resonant peak can be measured, they also alter the dynamics of the pickup, making the attack slightly slower, with less amplitude.

Now, with an "over the top" PU like the X2N, I don't know if it will/could be heard - but I'd expect a X2N to be prone to squeal when covered. YMMV.

Good luck in your tone tests.

 

[Artie]

Re: What affect do added pickup covers have on tone?

Thanks freefrog. That was a really good article. It's the first time I've seen anyone do a more scientific examination of the subject. I'll have to reread it a couple more times to be able to take it all in, but it still seems to leave one question unanswered. And that is, does the sonic impact come from the eddy current moreso than the simple diffraction of the magnetic field by virtue of the close proximity of the metal? Again, I'll reread that article a few more times to see if I missed that.

I'd love to get a Duncan Psyclone and modify it have a switchable shorting bar across the cover gap, to see if I could actually hear a difference. I may just do that, but those pups are a bit expensive.

Edit: Hmmm. zZounds has these for a solid $50 below everyone else. I wonder if they're legit. I'm pretty sure zZounds is a reputable company.