Chrome vs nickel pickup covers?

[Dave Locher]

I am looking at smooth (no holes) metal covers to put on humbucker pickups. There are nickel silver covers with chrome or nickel plating, and copper with chrome plating.
Will these have different effects on the sound? If so, what are the likely differences between the three?

[Bill Raymond]

I can't speak from experience, but I would guess that you would have more eddy current losses in the copper covers, as copper is a better conductor. That would tend to cut the high frequencies a bit more than the others. However, you probably have to try them to see if there were any real discernible differences; some folks are more sensitive to tonal nuances than others and the construction of the pickup may also determine the extent to which the cover material has a material effect on the sound. Perhaps someone who has experience with these different covers will offer an opinion...

[Dave Locher]

Well, I am very sensitive to tonal changes but I once pulled gold-plated covers off the humbuckers in an old Ibanez with Super 70s and could not hear a difference.
The copper seemed a bit odd to me. But I'm guessing nickel and chrome plating would sound about the same on the nickel silver base metal? I assume the only significant difference would be appearance?

[David King]

I'm not aware of any copper covers being made, cheaper covers tend to be brass and the better ones will be nickel silver. Chrome plating generally has three layers, a copper primary layer followed by a nickel layer and then the final chrome layer.

[Dave Locher]

There are quite a few on eBay, made in China, that say they are chrome-plated copper.
I'm ruling them out because they aren't that much cheaper, and if it's true copper sounds like an odd thing to surround a pickup with.
But as far as I know chrome plated nickel silver and nickel-plated nickel silver should sound the same, right? At least within the range of human hearing. I prefer the look of chrome, but if there is a reason why nickel might sound better I'm happy to hear it. (No pun intended, I swear.)

[Daryl Kosinski]

As long as the covers are non-ferrous there should be very little if any perceptible change in sound. To induce eddy currents in a non-ferrous metal there would have to be a much larger current than is produced in a pickup. Ferrous metal might "load down" the pickup. In general the more iron in the magnetic "circuit" the less high frequency spikes get through. Think a 60 hz transformer has a lot more iron in it than a 400 hz with the otherwise same ratings. Aircraft use 400 hz to keep weight down. Gold, nickel, chrome, brass or any other non-ferrous metal is not going to matter much in this application.

[David King]

Daryl,
This is an interesting topic of discussion and I'd have to say that most pickup makers seem convinced that they hear a difference between brass and nickel silver covers. Pure nickel and some of it's alloys are magnetic materials and I made the mistake once of spraying nickel conductive paint inside a pickup cover to shield the coil and it totally dulled the tone to the point I had to strip it out to make the pickup usable. It's not hard for me to imagine the magnetic field is getting disrupted with even a thin nickel plating. Nickel silver is 60% copper and around 20% nickel with the remainder being zinc. It is not magnetic as far as I can tell.

I don't know of a way to measure eddy currents in a cover other than perhaps looking for tiny changes in the coil impedance. Presumably most anyone can hear the difference between an uncovered humbucker and a covered one so the cover must be having some effect.

[Dave Locher]

Wow, this is more interesting and complicated than I expected!
I have read over & over that covers change the sound, but the one time I pulled the gold cover off of an ibanez super-70 I was disappointed to hear no significant difference.

Am I now understanding correctly, that a copper cover might actually have less impact on tone?

[Daryl Kosinski]

I believe it doesn't matter much what a Metal cover is plated with.

[Dan Smith]

I prefer the look of nickel over chrome.
I can usually find most hardware in nickel except bridges.