Stacked P90

[Bill Scheltema]

Hi guys,

On a stacked P90 similiar to a Kinman is a typical P90 wound to Spec and a second one wound reverse then added to the bottom for cancelling? Or is the total# of winds divided in half and use 2 shorter coils to keep the same coil width? The second shot looks more like a wafer in between coils instead of two separate coils.

[big_teee]

I haven't wound one, but what I've seen looks like 2 standard coils stacked.
The coil is only 1/4" inside bobbin height, so half of that would be too narrow.
I am fixing to try the Strat Stacked that we have been kicking around.
I'm going to use the .781 inch rod magnets on those, and use a forbon devider.
My end goal on it is for both coils to use a continuous piece of wire.
One start and one finish.
On your Stacked P90, as long as you can get it in the route, and a P90 cover fits over it.
It should work fine.
T

[big_teee]

Here's the dimensions for the Seymour Duncan version.
Seymour Duncan [www.seymourduncan.com] - Products - Specialized - STK-P1

[Bill Scheltema]

Thank you big T, these pups will be going into custom builds I'm doing for Randy Bachman.

I take it that they will be connected similiar to a hummer but stacked?



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[big_teee]

Bill:
I don't know the answer to that.
I'm still trying to figure out how you make one coil north and one south.
If you magnetize the screws through both coils,
I would have the starts and finishes where you can swap them around.
Maybe others can chime in how to wire it.
Sonny, and Copper, got any ideas?
T

[Peter Naglitsch]

Maybe I'm thinking backwards here, but I think that the magnetic polarity is reversed in the bottom coil IF the magnets are placed between the two coils (the field throught the coils that is) and if so you shouldn't reverse the polarity of the coil. If you have the south poles in for both magnets, you will have a magnetic filed through the top coil that has the north pole on top. And the bottom coils will have south up so yeah, it seems to be right.

However there is more to the Noiseless P90 from Kinnman, Have a look at the steel plates divideing ans shielding the colis from each others. And there is probably a lot of other funky styff going on inside the coil, added steel to manípulate frequency responce and output from the bottom coil and similar stuff. I have tried to just add a coil for hum canseling in the electronics compartment, but thet changed the sound too much top be useful (with my getho version at least...)

[big_teee]

Maybe I'm thinking backwards here, but I think that the magnetic polarity is reversed in the bottom coil IF the magnets are placed between the two coils (the field throught the coils that is) and if so you shouldn't reverse the polarity of the coil. If you have the south poles in for both magnets, you will have a magnetic filed through the top coil that has the north pole on top. And the bottom coils will have south up so yeah, it seems to be right.

However there is more to the Noiseless P90 from Kinnman, Have a look at the steel plates divideing ans shielding the colis from each others. And there is probably a lot of other funky styff going on inside the coil, added steel to manípulate frequency responce and output from the bottom coil and similar stuff. I have tried to just add a coil for hum canseling in the electronics compartment, but thet changed the sound too much top be useful (with my getho version at least...)

With a stacked pickup with Rod Magnets, you have a north and a south polarity coil.
If you run screws through 2 coils, then put the magnet at the bottom, both coils would be either north or south?
Or maybe justing wiring one in reverse will correct this?
If anyone has experience with this and would like to share please do.
T

[Stratz]

Maybe I'm thinking backwards here, but I think that the magnetic polarity is reversed in the bottom coil IF the magnets are placed between the two coils (the field throught the coils that is) and if so you shouldn't reverse the polarity of the coil. If you have the south poles in for both magnets, you will have a magnetic filed through the top coil that has the north pole on top. And the bottom coils will have south up so yeah, it seems to be right.

I'm not sure that's correct Peter. I've only made them out of 1/8" forbon bobbins with alnico rods (kind of like a stacked Jazzmaster) but if you stack two P-90 coils with the bar magnets between the bobbins with like polarity's facing each other both coils will have the same polarity.

My father used to make them many years ago out of forbon but with nylon sleeves glued in to take the traditional P-90 screws and bar magnets. I'm pretty sure the top bobbin was 5/16" and the bottom was 1/8". I don't recall what gauge wire he used. They were tall but a standard P-90 cover would hide most of it.

[big_teee]

I'm not sure that's correct Peter. I've only made them out of 1/8" forbon bobbins with alnico rods (kind of like a stacked Jazzmaster) but if you stack two P-90 coils with the bar magnets between the bobbins with like polarity's facing each other both coils will have the same polarity.

My father used to make them many years ago out of forbon but with nylon sleeves glued in to take the traditional P-90 screws and bar magnets. I'm pretty sure the top bobbin was 5/16" and the bottom was 1/8". I don't recall what gauge wire he used. They were tall but a standard P-90 cover would hide most of it.

So did he put the magnet on the screws at the bottom and reverse wire one bobbin?
Thanks Stratz for the help!
T

[Stratz]

I'm going back in my head to the early 80's Terry but I'm almost positive the magnets were in between the bobbins.

[davos]

On the first photo, if you look just above the PCB, it looks like the end of an Alnico Bar, inbetween the 2 coils.

[Bill Scheltema]

So I guess the idea is to get the bottom coil to be weaker so it doesn't take away from the top coil and compensate with metal spacing and shielding.
So then if using screws that only went to the bottom of the top coil and slugs in the bottom coil separated from the upper half would be an option?

Bill

[big_teee]

So I guess the idea is to get the bottom coil to be weaker so it doesn't take away from the top coil and compensate with metal spacing and shielding.
So then if using screws that only went to the bottom of the top coil and slugs in the bottom coil separated from the upper half would be an option?

Bill

Did you see the other thread I opened in the main area?
Trying to get my head wrapped around how it works also.
http://music-electronics-forum.com/t32414/

[David Schwab]

So I guess the idea is to get the bottom coil to be weaker so it doesn't take away from the top coil and compensate with metal spacing and shielding.
So then if using screws that only went to the bottom of the top coil and slugs in the bottom coil separated from the upper half would be an option?

Bill

The idea is the bottom coil is out of phase with the top coil. This makes the pickup thin sounding.

If you totally isolate the bottom coil from sensing the strings, then you take care of some of that problem. But then you have a dummy coil in the circuit, and that tends to dull the tone.

So what the newer designs do is wind a lower resistance bottom coil, but then make it more sensitive to noise than the top coil, and then they shield the top coil with steel.

Here's an example. This is a DiMarzio Virtual Vintage Pro Strat pickup:



This is a very good sounding hum canceling single coil. The top coil has a magnetic shield around it, and the shield is also grounded. It has 6 alnico magnets. The top coil reads 8.53k.



Here you can see the bottom of the top coil shield.

The bottom coil is wound to 2.45k, and has no magnets. Instead, it has ten steel slugs, and it has no shielding. The slugs increase the inductance in the coil.

The two coils are wired in series.

This is similar to the Kinman design (I think he was first) and the new Duncan design.

[Bill Scheltema]

Thanks for the input guys. I'll have to put some thought into this. That magnetized shield looks thin to me.

Bill