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New here. Messing around with making my first pick-ups. Any thoughts on metal bobbins and cover material. Obviously steel would be counter-productive, but what about non-ferrous metals, aluminum, copper, brass, silver??? Thanks
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One word, well 2 actually
Eddy Currents........... -
24 hours, 40 views, one 2 word reply. Hmmm???Comment
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Sorry we haven't been more helpful but you only have to paddle at the edge of this lake we call pickup making to know what materials are used in pickup bobbins and covers. So invest a little and learn a lot.sigpic Dyed in the woolComment
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Bobbin and cover material
Why metal for bobbins and covers. I can at least understand using metal covers, but bobbins? I don't know. Plastics and other stuffs are easier and cheaper to work with, than metal.Comment
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Having been referred here by an email link from Jason Lollar I first did several searches and found very little info related to my question. I then posted my question.
I know what materials are used and have been used. I also know what bobbins and covers are easily obtained.
I will be making my own bobbins (and covers) because the pick-ups are not standard sized nor are they for standard instruments. I 'do' metal so metal fabrication (and casting) is easier for me than plastic. I'm interested in information related to the effects of non-ferrous metals on the performance characteristics of magnetic pick-ups for stringed instruments. Anyone with actual experience or knowlege??? Thanks in advance.Comment
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Well here's something for you. People use aluminium for shielding purposes. Why not make yourself some aluminium pickup covers just like the very first PAF covers.sigpic Dyed in the woolComment
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I'm not sure anyone has actually made a pickup with metal bobbins that is usable. The problem is that metal parts in the vicinity of a magnet are prone to eddy currents which flow on the surface of the metal. These in turn create their own magnetic field which opposes the field that created them. This will tend to cancel out high frequencies, and is the reason why a non-ferrous pickup cover will dull the sound. The more conductive the metal, the worst the effect. This is why brass covers and bottom plates are not as ideal as nickel silver, which is less conductive electrically.Originally posted by tusong200 View Post
The metal doesn't have to be ferrous to cause problems, and one reason for this lies in the fact that all magnetism is due to circulating electric currents. In magnetic materials the magnetism is produced by electrons orbiting within the atoms; in most substances the magnetic effects of different electrons cancel each other out, but in some, such as iron, a net magnetic field can be induced by aligning the atoms.
So electric fields and magnetic fields are one in the same... just different aspects.
The one metal bobbin pickup I know about is made from laminated steel transformer core type material. It's a Tele bridge pickup made by Kinman, and it's the bottom coil on a stacked humbucker. I believe the reason he does this is to increase the inductance of the pickup, while eliminating eddy currents, which don't form as readily in the laminated steel, since the thin laminations have less surface area.
I make non standard size pickups.. well it is a standard size, but I can't find commercial parts that I want to use, so I make my own bobbins using phenolic PC board material. When I'm prototyping something I like to use the perf board, because I can score it with an exacto and snap it to the size I want.
You could mill the stuff if you wanted to... I use a small router for the solid board material, and a router bit in my drill press as a poor man's drill mill! So I think your metal working gear would come in handy!It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein
http://coneyislandguitars.com
www.soundcloud.com/davidravenmoonComment
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David, Thanks for the info and the link to Kinman's site (lots of info there).
Virtually every garden variety humbucker has a brass baseplate usually in direct contact with the magnet and usually in very close proximity to the adjustable poles. Are the eddy currents not a problem here?? Maybe too far away from the point at which the strings pass thru the magnetic field?? Or is the concern not so much between the magnet and the metal but more so between the windings and the metal?? Inquiring minds want to know.
And thanks for your tip about the phenolic material.Comment
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I don't make many humbuckers... but I think the others here will say that brass covers and bottom plates sound different from nickel silver. You can hear the difference when you don't have a cover on a humbucker. Since the cover is not magnetic*, and can't effect the field, the difference in tone with the cover must be due to eddy currents.Originally posted by tusong200 View Post
Fender pickups don't have metal base plates, and would most likely sound quite different with one. The bottom plate on a Tele is a good example.. beside changing the magnetic field, it probably changes the tone due to eddy currents. One maker (I think GFS) sell Strat pickups with brass bottom plates that they claim warm up the tone by reducing the top end.
The thinner the metal the better though, which is probably why Lawrence L500XL with the thin blades and plastic case, are much brighter than something like a DiMarzio X2N with the thick blades and metal bass plate.
Bartolini used to sell high output humbuckers with exposed coils and laminated steel blades. They had a nice vocal sounding midrange.
*actually everything is magnetic to some extent.It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein
http://coneyislandguitars.com
www.soundcloud.com/davidravenmoonComment
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only the cheap humbuckers have brass plates- I dont claim to have tested to see if a brass bottom plate sounds different than a nickel silver one but for a pickup cover it does make a difference.
I know someone that made some aluminum bobbins and he told me they killed the top end- I have never done the testing to confirm that but aluminum definately creates eddy currents- put a piece of aluminum between two large magnets and when you move it it feels like its being attracted to the magnets.
The only time I recall seeing aluminum used for a bobbin was out of a 1930's rickenbacker bass
http://i8.photobucket.com/albums/a3/...seShoebass.jpg
I have no idea what it ended up sounding like as it went into the smithsonian and I will probably never see one again. Its the bass you may have seen in a book- its made with a metal tube for a body not the more art deco looking one.Comment
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maybe i also remember seeing aluminum on a 50's 10 string rick steel guitar- maybeComment
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It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein
http://coneyislandguitars.com
www.soundcloud.com/davidravenmoonComment
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took me a while to find a photo of it but here it is
http://i8.photobucket.com/albums/a3/...ckBass1930.jpg
The magnets in the previous photo at the widest point are 7 inches long so that will give you some idea of the size of it.
I have worked on lots of these old ricks including the violins- The violins are all bakelite and look like a miniture rifle.Comment
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slightly later violins were all bakelite that isComment
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