how do they construct a hum canceled p-90?

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Greg Martin
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how do they construct a hum canceled p-90?

Post by Greg Martin »

Hi Ive read about hum canceled p-90s from fralin, kinman etc, but have never seen an exploded view of one or an explaintion of how it works. Anyone know??

David King
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Re: how do they construct a hum canceled p-90?

Post by David King »

Greg, do you know how to look up patents from the US patent office? Google has a very slick interface that works quite well.
If you google Kinman patents you'll find several numbers I'm sure and they will all include links to previous art as well as links to newer patents that reference Kinman's designs.
Hum-cancelling P-90s are mostly of the stacked variety. Some use a magnetic field deflector to improve the efficiency. I posted photos of the Kinman's insides over at the music-electronics forum
You'll need to fabricate some parts to do something like that. What about just using a dummy coil nearby?

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Beate Ritzert
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Re: how do they construct a hum canceled p-90?

Post by Beate Ritzert »

Would work but shift the resonance. Higher if wired parallel. You need to add at least a small capacitance to compensate.

Patrick Macy
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Re: how do they construct a hum canceled p-90?

Post by Patrick Macy »

These look interesting where they are simply stacking another coil wound the reverse direction for noise canceling. However, I am not positive if the poles go through both coils or just the top coils.
http://www.stealthtone.com/StImage/P90-Br-Pik1.JPG
Last edited by Greg Robinson on Tue Jan 15, 2013 3:13 pm, edited 1 time in total.
Reason: Converting inline image to link - staff

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Greg Robinson
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Re: how do they construct a hum canceled p-90?

Post by Greg Robinson »

Hi Patrick, please note that we ask you only post images you created yourself, as otherwise is a violation of copyright laws. I've converted the inline image you posted to a link. Please review the forum rules.
Thanks.

Also, the poles most likely do go through both coils, as the core material affects their inductance, and it is this parameter of the coils that you want to most closely match for good hum cancelling. There are other ways to match the inductance, like using different numbers of turns and different core materials, but keeping same/same is certainly the easiest.
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David Schwab
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Re: how do they construct a hum canceled p-90?

Post by David Schwab »

The Frailin pickups are sidewinders, like the old Lawrence L-250s. In a sidewinder the two coils lay on their side with the tops facing the keeper/pole pieces. This way there is a single point in which the pickup samples the string, and it sounds like a single coil. They are a little less efficient, so the output is often a little lower. But that can be compensated with winding it hotter.

I don't know if he has the magnets in the coils, or under them. They need some kind of core, so putting them in the coils makes sense. But they can also have a steel core and have the magnets on the outsides. You can find some photos of his pickup on the internet.

I was in a band at one point with a guy with 2 of the Fralins in his PRS. They had a nice chimey tone like the old P-90s. They have better low end than stacks, which tend to be thin sounding because the two coils are out of phase, and it cancels out some low end. So stacks are always wound hotter to make up for it.

I make some sidewinder style pickups.

Art Davila
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Re: how do they construct a hum canceled p-90?

Post by Art Davila »

I have seen the kinman p 90 hx pickup in a friends tele / paul hybrid.
sound was very much full clear tone but no hum, so the humbucking aspect work great.
I have to say that my next project, a billybo clone, I am torn between putting in the same tv jone pickups or those kinmans. I really liked the sound of them.
I have a lot of experience on how "not" to do things.

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Shawn Ball
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Re: how do they construct a hum canceled p-90?

Post by Shawn Ball »

I significantly reduced the hum in my LP Special DC style build by placing an "air coil" in the control cavity. I used an old ceramic Tele bridge pickup sans the magnet. Wired it up in series after the pickup switch, and can bypass it with a push/pull pot. It doesn't cut 100% of the hum, as the number of windings in the Tele pickup were not a perfect match for the P90s, but it cuts the hum by probably 12db (1/4 or less perceptible hum when engaged?) at my house, where 60 cycle hum seems particularly bad with all my single coil based guitars. When I play the LP Special at church, the pickups are very quiet on their own, and are completely him free with the air coil engaged.
SDB Guitars - turning exotic woods to sawdust and fireplace scraps since 2001 :)

Art Davila
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Re: how do they construct a hum canceled p-90?

Post by Art Davila »

hmmm....
If you know the windings or inductance of your pickups,
I wonder if you could improve the hum canceling? Sounds interesting did you come up with that or did you hear about it and decide to give it a try?

Did this mod change you tone much? If so how did it impact the tone?
I have a lot of experience on how "not" to do things.

David King
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Re: how do they construct a hum canceled p-90?

Post by David King »

Getting full canceling isn't as easy as getting the turns*area exactly right you also need to mimic the inductance with a similar core.

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