Paf offsets

[Possum]

follow up....

There are some cool videos of Gene Vincent on youtube for you strat guys. The guy playing in those videos has a brand new strat and brand new bassman, shrill shrill shrill.....great videos

[David Schwab]

Torus? Do you mean rod? Antennas are rods. Or do you mean a thick-walled ferrite bobbin? Can you draw a picture from memory and post it?

OK.. hard to draw, unless I use a 3D program... so let me try to describe it this way first...

Take a donut and squish it into an oval, the shape of a bobbin. It's still has a round cross section. It's solid ferrite material. Now take your wire and wrap it around the donut, up through the middle of the hole.

Here's a 2D illustration. I've never seen anything like this since. Note that the wire may have wrapped around the curved parts, but this is how I seem to remember it.

[Joe Gwinn]

OK.. hard to draw, unless I use a 3D program... so let me try to describe it this way first...

Take a donut and squish it into an oval, the shape of a bobbin. It's still has a round cross section. It's solid ferrite material. Now take your wire and wrap it around the donut, up through the middle of the hole.

Here's a 2D illustration. I've never seen anything like this since. Note that the wire may have wrapped around the curved parts, but this is how I seem to remember it.

Hmm. The way it's drawn it cannot have worked because the torus part is self-shielding, and the magnets in the eye of the torus will have no effect.

[Joe Gwinn]

There is a difference between dielectric constant and dissipation factor. I agree that dissipation factor isn't an issue at audio frequencies. However, dielectric constant is an issue IMO, because it's what determines the self-capacitance of the cable or pickup, and hence the frequency of the resonant peak.

Let's treat pickups and cables separately.

Pickups: The dielectric constants of all likely wire coatings and potting materials are all approximately 3.0, and as you mention, the dissipation constant isn't significant. So, the material from which the coating and potting material is made will not much matter. Typical self-capacitance is about 100 picofarads.

So long as the coil is kept dry. Water has a dielectric constant of about 80, and is very lossy (high dissipation constant), so a little moisture in a coil is devastating. This is why Fender invented wax potting. See US patent 4,885,970.

For example, PVC can have a dielectric constant anywhere between 3 and 6, depending on how it's made, and the temperature. Polythene has a dielectric constant of 2.2. So a PVC screened cable could have anywhere between 1.4 and 2.7 times the capacitance per foot of a PE one. That would probably make an audible difference in the mid and high end response when used as a guitar cord. Better quality guitar cords do seem to have PE dielectrics.

Cables: Cable types do vary greatly in capacitance per foot, and in length, so the net capacitance imposed on the pickup coil is easily 1,000 picofarads or more.

The self-resonant frequency of the assembly will therefore be the inductance of the pickup and the sum of cable and pickup capacitance. So, the cable capacitance will dominate.

Low-capacitance coax goes one step farther, using foamed polyethylene dielectric, which is more air than plastic.

Some pickup makers specify the resonant frequencies of their PUs. Is that with cable capacitance or without? If without, that implies the self-capacitance is significant. I personally believe that it is significant and not swamped by the cable.

I think you are imputing too much cleverness and malice, when simple sloth will do. From the pickup makers' standpoint, he cannot control or even know what cable will be used with his pickups. So, he has two options. Either use no added "cable" capacitance (very common), or use a standard load (say 470 pF, as done by Lemme). Neither approach is perfect, so just pick one.

Or publish the typical self-inductance and the self-capacitance, and let people compute the answer for their setup. But I don't know how many people care that much.

That also leads me to believe that magnet wire can only have a "sound" in so far as its diameter and enamel build [thickness] influence the self-capacitance and self-inductance of the coil.

I believe that this is correct.

If you discount self-capacitance, the only mechanism left for magnet wire to influence the sound is, like another poster said, how many turns you can get on there and how tightly it packs.

Not quite. The physical shape and dimensions of the coil also matters.

[Possum]

diagram

is the part the wire wound around you said is ferrite? the part the wire is wrapped on is magnetic material? I don't see how that could work. Are the pole pieces magnets? You said these were humbuckers? So there were two coils like these? Very weird idea, how did they sound? you'd have to hand wind literally these things and would be real low impedance.....very strange....

[NightWinder]

Not quite. The physical shape and dimensions of the coil also matters. (joe gwinn quote) Thats exactly what I have expressed all along....COil shape

[David Schwab]

Hmm. The way it's drawn it cannot have worked because the torus part is self-shielding, and the magnets in the eye of the torus will have no effect.

I thought it was very odd as well, but that's how they were made. Nothing on them was usual, except a bar magnet and the screw poles. I remember lifting one torus out and wondering how they wound that coil. I had never seen cloth covered wire in a pickup.

This is what the guitar looks like. I made a mistake with the model.. it was a 30/30, not a 10/10.

[Joe Gwinn]

I thought it was very odd as well, but that's how they were made. Nothing on them was usual, except a bar magnet and the screw poles. I remember lifting one torus out and wondering how they wound that coil.

There are torus-winding machines. It's a two-step process. One inserts the C-shaped bobbin through the eye of the torus, winds the wire onto the bobbin (allowing it to span the gap in the C), and then winds the wire from the bobbin onto the torus.

I had never seen cloth covered wire in a pickup.

It could be intended to space the turns out, which is what double and triple build on magnet wire does.

Cloth (and especially cloth enamel) covered magnet wire is widely used for radio frequency (RF) coils and especially for high-voltage coils (RF or not). The coil is wound dry, and then impregnated with varnish and/or wax, which glues everything together, and insulates everything as well. The cloth is usually cotton, although silk has been used. Spacing the metal out both reduces self-capacitance and increases the ability to withstand high voltages.

This is what the guitar looks like. I made a mistake with the model.. it was a 30/30, not a 10/10.

They look like ordinary humbuckers from the outside. If you ever get another look inside, take a picture.

[David Schwab]

is the part the wire wound around you said is ferrite? the part the wire is wrapped on is magnetic material? I don't see how that could work. Are the pole pieces magnets? You said these were humbuckers? So there were two coils like these? Very weird idea, how did they sound? you'd have to hand wind literally these things and would be real low impedance.....very strange....

Under the two donuts was a bar magnet which contacted the 12 screw poles, which were threaded into some kind of keeper. That part I don't remember too well, but the pickup's case was black plastic, so the screws were threaded into something metal, which contacted the magnet. That is the most "normal part of the pickup. I handled all the parts, so I know that the donuts were indeed some kind of ferrite material... felt just like an antenna core.

There were indeed two such coils, and they were wired in series. The pickup must have been somewhat low impedance, as the stock pots were only 100K. However it sounded kind of dull like that, and when I changed the pots for 500K units, it became much brighter sounding. It really sounding like it had single coils... very bright and chimey. One interesting thing was if I flipped over a torus, the two coils were then out of phase.

Here's a recording I did back in 1984 with that guitar [Run!]

This was recorded with two cassette decks, and I'm playing both bass and guitar... This is from a very old cassette which has a big drop out in one part of the song. You can hear how bright those humbuckers are. I think I was plugged into a compressor and right into a Tapco mixer (boy that brings back memories!)

Wish I kept that guitar. The neck was on the narrow side, but not as bad as a Ric.

I emailed a guy who runs a Shergold/Hayman website... asked him if he knew anything about the Re-An humbuckers. They have intrigued me ever since.