winding capacitance theory question

[Mike Sulzer]

You took even more turns off; that lowers the capacitance, and it lowers the inductance which reduces the effect of the remaining capacitance. You did not get the effect you wanted because you already did not have a problem with coil capaicitance.

Your response is relatively flat in the top end compared to a normal pickup, which has a peak there. Sure, all those other things can be a problem, but you have done the key experiments to answer your question. You do not have a problem with coil capacitance.

[David Schwab]

Plus the peak is higher than normal. Often low impedance pickups doesn't seem as bright because they don't have the upper mid peak.

[dcoyle]

Thanks to all for the info. It has been an education.

If someone is feeling flush, I see there is a gibson LP Bass pup for sale on ebay for $275. Anybody feel like they are that curious?

After chasing the sound I remember from days of yore, I have new respect for my existing pups, Fender RI jazz and Mui Grande pbass.

Thanks, guys.

Dan

[David Schwab]

I don't know if it's the same seller, but someone has three of these and he wants $200 each! I sent him a question asking if he could take a reading of the three taps (so I would know if the pickup was good or not)

I just got a reply and he's going to measure them at work later today.

But here's where the so-called "vintage" market gets stupid. $99 for a KNOB from a LP recording bass!

1969 GIBSON LES PAUL RECORDING GUITAR/BASS "BASS" KNOB - eBay (item 300356309281 end time Feb-08-10 06:23:36 PST)

Greed is rampant, and the fact that people buy this stuff makes it worse.

[David Schwab]

And the answer is... 16, 32, 64 ohms

[dcoyle]

Thanks ever so much for posting that info, David.

So, if it is 28 ga, which is 65 ohms/Kft, that is about 246 ft of wire, 492ft, and 985 ft. If the median turn is about 5", that's about 633 turns, 1267 turns and 2534 turns.

My memory is that the thinest tap was too thin to be of use to me, what ever my taste was 35 years ago.

Dan

[David Schwab]

Les Paul thought that the one setting sounded best, probably the highest one, and that they should have left it like that.

[David Schwab]

Oh, one thing I forgot to mention. With the LP Triumph pickups, they are stacked humbuckers, and the top and bottom coils are in series. This is true of each tap also.

So you have to divide the total resistance... i.e., the 16 Ohm coil is actually two 8 Ohm coils (top and bottom) in series. So the inside coil is 8 Ohms, the next layer is 8 Ohms and the outside layer is 16 Ohms.

The LP Recording guitar was the same, but with no taps.

On a humorous aside, I found two web sites that claim the LP recording pickups were made by DirtyWorks, aka Overlend, aka EMG. This ignores the fact that DirtyWorks came into existence in 1976 while the LPR came out in late '69/70. Oh and that EMG pickups do not have low impedance coils.

[dcoyle]

David,

One thing I remember, vaguely, from 35 year ago was that the two outputs of four wires are isolated from each other. When I look at photos of the control cavity on ebay of LP's, it looks like both sets of windings are switched. That is to say the dummy coil is not in series with the active coil inside the pickup, it is switched externally, I think.

So wouldn't the fellow selling the pups have reported the resistance in one coil?

Did you ask him to measure brown to green, or whatever?

Thanks

Dan

[David Schwab]

David,

One thing I remember, vaguely, from 35 year ago was that the two outputs of four wires are isolated from each other. When I look at photos of the control cavity on ebay of LP's, it looks like both sets of windings are switched. That is to say the dummy coil is not in series with the active coil inside the pickup, it is switched externally, I think.

So wouldn't the fellow selling the pups have reported the resistance in one coil?

Did you ask him to measure brown to green, or whatever?

Thanks

Dan

OK I'm basing it on two different schematics I have. They show the top and bottom coil being switched into series, so that's each tap into the same tap on the other coil. The taps them selves are of course like a series of smaller coils.

Here's one of them:

[dcoyle]

Hey David,

I really appreciate your posting that schematic. When I saw an LP schematic, 30 years ago, it seemed much more complicated.

So it seems, if the coils are switched external to the pup, the fellow was measuring a single coil at 16, 32 and 64, que no?

Thanks

Dan

[David Schwab]

Hey David,

I really appreciate your posting that schematic. When I saw an LP schematic, 30 years ago, it seemed much more complicated.

I have that older schematic, and it is a rats nest! I also have a drawing of the control compartment by Gibson from about the same time frame.

I notice this one says it was redrawn in '75. I got that from Gibson's website.

So it seems, if the coils are switched external to the pup, the fellow was measuring a single coil at 16, 32 and 64, que no?

I asked him to measure between the brown and green, brown and blue and brown and red. So 64 Ohms would be between brown and green. 32 is brown and blue, and 16 is brown and red.

The top and bottom coils are tapped. That means they wound so many turns, and then took that end out to a wire, then continued winding, and took out another tap, and so on. You can see in the schematic that the start wire is green and the finish is brown. In between those you have two taps that are red and blue. The tone selector switch switches between the coils.

So however the top coil is switched, the bottom coil is switched the same way to maintain hum cancelation.

I'm going to redraw each selection for clarity at some point so I can better trace what's going on.

[dcoyle]

Actually, the answer is...

I bought two of the pickups that were advertised in that ad. The dc resistances are not 16, 32, and 64 as stated on the ebay ad.

They are 25, 52 and 114 ohms.

I am going to post the details in a new thread, "Les Paul bass specs"

Dan

[David Schwab]

I bought two of the pickups that were advertised in that ad. The dc resistances are not 16, 32, and 64 as stated on the ebay ad.

They are 25, 52 and 114 ohms.

I am going to post the details in a new thread, "Les Paul bass specs"

Dan

From a few things the guy said I had a feeling he didn't know how to use the meter. He also said it was known to be off by a percent or so, so he changed the numbers.

I might have bought the set, but I didn't have the money.