Pickup Covers - Brass Vs. Nickel Vs. "Plated with Copper"

[craggyisland]

Morning Folks.

I hope you dont mind me doing a bit of "public musing" with this stuff.

A bit of background might explain what i'll be doing if i'm going to be a bit more active.

I'm not much of a guitar player - as far as i can tell, i've got a tin ear frankly - but I've got a bit of a love/hate thing going on with pickups, and being some brand of engineer, I've always been interested in debunking/proving some of the myths that seem to have grown up along with some of them parts - and... well? I've got access to most of the parts required to build pickups through work, so i figured - why not see whats what with "parts of parts" eh?

So, today, I've got a Telecaster neck pickup on my bench - and i wanted to see how the cover effects the peak frequency. (I'm sure its been done to death at this point, so sorry for the repetition!)

But i got to thinking - whilst its pretty clear that brass and German silver/Nickel makes a difference - theres some argument that with Humbuckers that "no copper" covers also behave differently.

Now, when i say "no copper" (and excuse me if i'm teaching you to suck eggs!) - i'm reffering to the copper "underplate" thats used in the process of electroplating, underneath the "colour layer" (it does have a purpose, it makes the finish on the final colour layer much smoother, much less prone to failure - from an aesthetic point of view, its great... but no one seems to know what it does tonally.

So - here you go! (excuse the text dump!)


Whats interesting here, is that whilst we see what we'd expect from an unplated (no copper) German silver cover (excuse the habit of calling it Nickel!) in red - the "nickel with copper" behaves much more like an unplated brass cover then i'd have ever imagined.

So, in all likelihood, theres probably something in the "copper doesn't help" argument - seemingly, any large quantity of copper within the cover (either layered above the base material, embedded in its alloy, or both) really does smash the resonant peak down, and flattens out the Q factor. (its worth noting that i didn't test "plated WITHOUT copper" - they exist in humbucker covers, but i've never seen a Telecaster one)

Quite an interesting one from my point of view, because i've always thought it was a load of nonsense - but there you go! Ever days a school day eh?

Go forth, use the info as you fancy ;-)
Cheers

Craggy.

[stratotarts]

Yes, it all makes sense. The area directly between the poles and strings is particularly sensitive to differences because it is where the time varying magnetic field from the string is concentrated. So while metallic differences make a difference anywhere in the pickup, that difference is usually quite small unless it is actually near the string field. It is only the magnitude of the difference that surprises me a little bit here. But all plating is not equal. Since your samples come (I assume) from completely different supply chains, one can not perfectly eliminate certain variables. The "unplated nickle silver" vs. "nickel plated nickel silver" may not be a clear look at the plating, due to the fact that each German silver base material might not be the same. Of course, the only place you could really do a perfectly clean test would be in a factory, or to plate them yourself. So it's still interesting to make close comparisons.

[craggyisland]

Youright Ken man - you well?

Samples actually are all from the same supply chain - a plated w/copper "under" is the same "thing" as the as the unplated - same mass, same shape, same style, same positioning against the poles, same part number (I'm not quite in the factory, but I'm not a million miles away ;-) (I'm slightly further removed from the plating factory though!) )

Copper under plate thickness is potentially a variable, but at that point, but were getting into the realms of fantasy if we think we've any control over that - but...

I suppose this test has opened the door to a copper vs. No copper test if nothing else. Not something I'll be able to do with a tele pickup, but I've all the bits in stores to run it with a humbucker again - so I'll get that run off at some point in the next month or so. I'll post what I find.

[antigua]

Thanks for doing this test. When people are talking about plated versus unplated nickel silver covers, this is good evidence that the unplated cover will be more tonally transparent. I don't know where you got an unplated brass cover, I'm curious what that even looks like. 

I think thickness plays into it to, because I have a rather thick unplated nickel silver Gibson humbucker cover, and the attenuation was only slightly better for the unplated cover. The red is a thicker unplated nickel silver cover, the black is a thinner, but plated nickel silver cover. 

[craggyisland]

May 6, 2021 20:48:12 GMT -5 antigua said:

Thanks for doing this test. When people are talking about plated versus unplated nickel silver covers, this is good evidence that the unplated cover will be more tonally transparent. I don't know where you got an unplated brass cover, I'm curious what that even looks like. 

I think thickness plays into it to, because I have a rather thick unplated nickel silver Gibson humbucker cover, and the attenuation was only slightly better for the unplated cover. The red is a thicker unplated nickel silver cover, the black is a thinner, but plated nickel silver cover. 

Ask and you shall receive Antigua my man ;-) (my work carry them in Telecasters, Mini humbuckers, burns, few others - but as you can imagine - they're slow sellers, so its a bit sporadic (brass is a dirty word when it comes to covers aint it?)

I've got a humbucker crossing my desk this afternoon all being well - and i'll be able to test that for Nickel Silver with copper under plate, nickel silver plated without copper, and nickel silver unplated.

If uncoppered shows similar qualities to unplated, then that'll be "nice" (as i shout to the sky and wonder where i'm going to get these things on the shelves in stores!) - but hey, atleast we're learning eh? ;-)

[antigua]

Thanks that's interesting. I think it could be a cool look for a pickups, but the attenuation of brass is high, unplated or not, so unless it has cuts that stop eddy currents, I don't think I'd go for it myself. I know some guitarists actually appreciate the muffled high end, but I've always gone for jangly cleans.

[craggyisland]

Posted by antigua
May 7, 2021 at 10:26pm
Thanks that's interesting. I think it could be a cool look for a pickups, but the attenuation of brass is high, unplated or not, so unless it has cuts that stop eddy currents, I don't think I'd go for it myself. I know some guitarists actually appreciate the muffled high end, but I've always gone for jangly cleans.

Haha, i dont know if it was the same in your house man, but it brings back bad memories of earning my pocket money as a kid, polishing the brass fireplace. Tone be damned - my mother wont stand for those finger prints if i want a comic this weekend!

Its a funny one if you ask me - some pickups, we expect brass - Tele necks, Filtertrons, Burns Trisonics - it was likely, never used for any sort of tonality when the pickups were designed, but its hung around right up to the modern day, despite being "worse" (and they're all fairly bright and breezy pickups too) - suppose it becomes a bit of a mix between "what we've come to expect tonally" and "these are too bright without the cut" - but yeah - always surprised that there's still such big demand for brass covers in some pickups, and not others. (I'm a single coil man myself, so metal covers can take a running jump as far as i'm concerned - just another thing to keep the finger prints off!)

[antigua]

That's a good point about the finger prints, but I think you can cover the brass with some sort of clear finish, like polyurethane, so that it won't tarnish. It might not hold up, though.

[craggyisland]

May 10, 2021 11:38:10 GMT -5 antigua said:

That's a good point about the finger prints, but I think you can cover the brass with some sort of clear finish, like polyurethane, so that it won't tarnish. It might not hold up, though.

The funk lives in the grime anyway ;-)

[stratotarts]

I've always thought tarnished brass covers would look great on a steampunk themed guitar...

[craggyisland]

I've always thought tarnished brass covers would look great on a steampunk themed guitar...

Yeah man - i think, honestly, theres where most of them end up to be honest (or some really "I've dragged this behind the car for a week" relic jobs) - its not without its charms, but as you can imagine - Brass is still a dirty word (maybe rightly so!)

[frets]

They look great on a Dark Green or Dark Blue Guitar.😺

[ecmalmo]

Took some pictures of an unplated and plated cover just for fun. The copper layer is really thin and sands off easily, revealing the nickel beneath. It might fool someone thinking it’s a brass cover beneath the chrome if you dont sand through. The unplated cover is obviously just greenish silver all the way.

Edit: I got this plated cover from Donlis on Aliexpress.

[veliko]

Very useful info craggyisland!

I will take your word for granted regarding shape and content of the covers you examined. I am however curious would these effects of flattening the peak diminish by reducing mass/volume of these covers? Is it the mass or the volume (I am aware of the tight relation these 2 parameters have) of these parts that that does this? 

[stratotarts]

I did try thinning a cover. It was a few years ago, so I don't have details. All I remember is that I ground as much off as I dared, without damaging the cover. It made no measurable difference (it was not possible to be perfectly exact, because the cover had to be removed/replaced in between tests). My conclusion, considering results of other tests involving the effects of copper foil, that the material can not be so thick as to be substantially rigid, or else it will incur significant losses. Because ohmic losses are proportional to the area of the cross section of the conductor, it comes as no surprise.

[antigua]

Apr 23, 2022 19:37:40 GMT -5 stratotarts said:

I did try thinning a cover. It was a few years ago, so I don't have details. All I remember is that I ground as much off as I dared, without damaging the cover. It made no measurable difference (it was not possible to be perfectly exact, because the cover had to be removed/replaced in between tests). My conclusion, considering results of other tests involving the effects of copper foil, that the material can not be so thick as to be substantially rigid, or else it will incur significant losses. Because ohmic losses are proportional to the area of the cross section of the conductor, it comes as no surprise.

I don't quite understand, it made no apparent difference if the cover was reduced in thickness, or did it, due to the reduction of conductivity? I'd like to know, because I'd divided on whether the attribute differences to thickness or plating layers, such as copper and gold over brass. And to complicate matters more, the potential thickness of that copper undercoat might be a factor, and to complicate things further, I've seen difference shades of "gold plating", so all gold might not be created equal when it comes to electrochemical gold plating.  I feel that gold covered pickups tend to show higher eddy currents on average, but I haven't done a study on it.