Challenging and exciting new design needs a guru !

[Mike Sulzer]

The original pickup is a great example of function following form...

Oops...

A slot would take care of the shorted turn aspect...

Since we are dealing with a tube, a single slot along the its length would still allow current to flow all the way around (along one side, then at the end, away from the slot, then back along the other side and around the other end in the same way). Cutting the tube completely in half lengthwise would be good electrically, but not mechanically. You do not have to cut all the way to the end, of course, but that would not make things that much easier.

[salvarsan]

Since we are dealing with a tube, a single slot along the its length would still allow current to flow all the way around (along one side, then at the end, away from the slot, then back along the other side and around the other end in the same way). Cutting the tube completely in half lengthwise would be good electrically, but not mechanically. You do not have to cut all the way to the end, of course, but that would not make things that much easier.

My quibble with the "shorted transformer primary" model is that the inductive coupling between the sensor coil and tube is weak.

Yes, it degrades the generated signal, but my guess is that eddy currents are the larger contributor. I have no way to model this.

[Mike Sulzer]

My quibble with the "shorted transformer primary" model is that the inductive coupling between the sensor coil and tube is weak.

Yes, it degrades the generated signal, but my guess is that eddy currents are the larger contributor. I have no way to model this.

Yes, the fluxes through the coil and tube are very badly coupled. Eddy currents do flow, but they are limited by the huge "leakage inductor".

By the way, the two ends of this pickup contribute signals that are out of phase. (One end has fields lines with vertical component pointing up, the other down.) This is truly a strange pickup.

[Rick Turner]

Mike, understood.

Just wrap a large diameter wire coil around the coil and only connect one end for shielding!

Of course that doesn't help the rest of what's so weird about the pickup...

Hey, have pole pieces poke out between the stacked magnets...make it even weirder...

[salvarsan]

By the way, the two ends of this pickup contribute signals that are out of phase. (One end has fields lines with vertical component pointing up, the other down.) This is truly a strange pickup.

Yes, indeedy.

The original design summed the pickups. The problem with these 6 pickups is that there is substantial crosstalk from adjacent strings. With that, why bother to bring them out separately? Gittler, for all his many talents, didn't grasp the magnetics -- not an easy thing in any era, to be honest.

Any hex pickup must contend with crosstalk. Gibson's hex pickup has the blades straddle the string instead of crossing them because the magnet field between pickups is less that way. Looky here:

UPDATE: Gibson's patent 7166794 lists -45 dB crosstalk between adjacent strings for the hex pickup. Compare this to 30dB for a good phono cartridge.

[David Schwab]

By the way, the two ends of this pickup contribute signals that are out of phase. (One end has fields lines with vertical component pointing up, the other down.) This is truly a strange pickup.

It's a tall single string pickup laying on its side. It's dumb, but I don't see how one end has field lines pointing up and the other down. It's just like a 3" tall Strat pickup laying on its side.



Problem is neither pole is pointing toward the strings!

[salvarsan]

Yes, the fluxes through the coil and tube are very badly coupled. Eddy currents do flow, but they are limited by the huge "leakage inductor".

It would be interesting to know the Gittler coil's inductance within and without the stainless steel tube.

[David King]

Since it's a coil on it's side couldn't we set a second pickup tube end to end and make the two identical poles face each other thus creating a sidewinder.. I guess that's maybe what Rick had in mind with the upright pole pieces between magnet segments. Couldn't the outside tube be non-conductive? A mirror coated glass tube for instance?

[Rick Turner]

Roland's hex pickups work like gangbusters for what they're intended to do.

In 1984 I made some tiny single coil pickups for a synth guitar project that Gary Kahler was going to do...that never happened. They were about 800 turns of #46 on 1/8" x 3/8" samarium cobalt magnets. The coils were all totally adjustable for height and string spacing. The coils faced a "normal" direction, and I was able to get better than 16 dB of separation from string to string.

The head of the project was Michael Stewart who had been in the "We Five" and was John Stewart's brother. He called the device "Walter Midi"...

I'll have to dig up the prototype and take a photo.

[Dave Kerr]

If the only design limitation is to have the pickups fit inside the tubes, why not just string a series of mini-Wal type bobbins inside?

[Rick Turner]

The have sliding switch contacts to turn on and off different sections of the tubular pickup.

And glass would be cool, but it would have to have a nice transparent conductive coating for shielding. Then you put in LEDs... Or better yet, small bulbs of tritium.

And you could call them "tube" pickups. Then guitar players would buy it...

How expensive can we make this thing? Wind with high purity silver...transparent shield glass tubes...tritium...discrete DC coupled buffers... Gee, 40 years ago I had clients who would have paid for that...

[Mike Sulzer]

Mike, understood.

Just wrap a large diameter wire coil around the coil and only connect one end for shielding!

Good for the shielding, maybe not for the "artsy" aspects!

[David King]

Dave Kerr,
The pickups are oriented parallel to the strings, not pointing up but yes, as long as there are two coils to each string with the N (or S) polarities pointing at each other in the middle, it might just work...

[David Schwab]

If the only design limitation is to have the pickups fit inside the tubes, why not just string a series of mini-Wal type bobbins inside?

Or a regular bobbin turned sideways. But a long coil like that will likely sound a bit dull.

So two small coils, à la Wal, would be the best bet. They could fit in the tubes, and even have small poles passing through.

Well these goes the free advice! lol

[Mike Sulzer]

It's a tall single string pickup laying on its side. It's dumb, but I don't see how one end has field lines pointing up and the other down. It's just like a 3" tall Strat pickup laying on its side.



Problem is neither pole is pointing toward the strings!

OK, I was thinking the coil must be pointing with the opening towards the string. Then the pickup is sensitive to vertical motion (towards, away from, the guitar "body") of the string like a normal pickup. A field line comes out of one pole and magnetizes the string at an angle, but with a vertical upward component, say. The field line going back into the other end has a downward vertical component as it passes through the string. (The component of the magnetization along the axis of the coil is what counts.)

If the coil is laying on its side so that the opening does not point at the string, well, then it is the horizontal motion (parallel to the guitar "body") that counts and the horizontal magnetization that is important. Then both ends contribute in the same polarity as you say. But I do not see how you get enough sensitivity with the string along the "side" of the coil.

Are you sure that the coil is in this orientation (opening parallel to the "body", that is, coil axis parallel to the body)?