P100 modifications

gwEm

A few months ago I got a 'Vintage' SG Junior with a P100 fitted.

It sounded very soulless, so I tried it with a few alternatives.

To cut a long story short last night I decided to have a go at modding it.

The P100 is formed of two vertically stacked bobbins with two bar magnets in between them. The pole pieces pass through both coils. The coils are wired in parallel to a typical Gibson shielded lead. The bobbins are each wound with an 18k coil.

What I've done is to remove the coil on the lower the lower bobbin from the circuit. I did this by unwrapping the paper tape on the lower bobbin until I reached the black and white wires connecting to the shielded output lead. Then I simply unsoldered the lower coil.

The DC resistance of the resulting pickup is of course 18k.

It definitely sounds a lot better than the noise cancelling version, but I'm still
not sure it is really good. It's definitely amusing though. The pickup is very hot indeed - hotter even than a BKP Warpig for example. The low end is a little muddy and it has a kind of 'scorching' tone to it.

I'll leave it fitted and see if I can find a use for it.

ICBM

I had a 90s LP Junior once which was the same, and I did the same to it. I think the P100 design may have changed at some point though - more recent ones don't seem to sound as bad.

I have also heard of wiring them with a resistor/cap network in line with the second coil, which retains most of the hum cancellation while improving the sound - http://www.blueguitar.org/new/articles/blue_gtr/gtr/lp_jr_spec_mod.pdf

I haven't tried this personally but I think it should work as described.

gwEm

I might give that ago at some point. Though it's not bad with a single coil as we've done.

Pehaps the P100 design has indeed changed, there is also the Billy Armstrong version of course (which he doesn't actually use) having mismatched coils.

Funkfingers

I have two of these things from my Gibson LP Junior Special. I considered performing the Blue Guitar modification but decided against because I also had a Duncan STKP-1 available. (Another stacked coil P-90 derivative only with 4-con + shield output cable.) The inevitable series/single/parallel experiments followed. I did not care much for any of the sounds.

There is an opinion in some quarters that coil proximity can influence string excursion and the overall tone - even if one of the coils involved is not in circuit. This may be the case with the P-100 and Duncan stack designs. I suspect that it may also be true of the Duncan P-Rails model.

The comparison to a BKP Warpig is valid. I suspect that the Gibson coils have been wound on the assumption that they will be run in parallel with a second coil. Some frequency cancellation will have been anticipated.

Perhaps, the best compromise for tone and noise-cancellation would be to run the lower coil of the stack via a mini trim pot. This way, the pickup as a whole can be run with a partial coil split. Hopefully, there is a sweet spot where it sounds acceptable and rejects the worst of the hum and interference?

ICBM

'Coil proximity' does not influence string movement. Magnet proximity can and definitely does, but a coil does not generate enough of a magnetic field to influence the strings at all unless it's carrying a large current, supplied by an external source. (eg the way a Sustainiac system works.)

Jez6345789

Unless you want humbucking would probably just reduce the windings on a single bobbin and mod it back closer to a p90 it looks like it's made from mostly the same parts.

you might need to knock up a simple base plate but it should sound better.

Funkfingers

The Duncan STKP-1 has a metal base plate. In my opinion, it sounds only marginally better than the Gibson P-100. Neither of these designs produces the "rudeness" of a good single coil.

gwEm

Interesting ideas!

I'm no Seth Lover, but in my experience a baseplate makes less of a difference the hotter you wind them. 

Still, it'd be a quick and easy change to patch both ends of the lower coil to ground.

Another thought with a baseplate would be to insert one between the magnets and the lower coil - a bit like a DiMarzio HS-3

gwEm

'Coil proximity' does not influence string movement. Magnet proximity can and definitely does, but a coil does not generate enough of a magnetic field to influence the strings at all..

Thats very likely true. But the lower coil definitely affects the inductance of the upper coil. How much I can't say, probably not much, but any conductor close to a coil will do that.

ICBM

gwEm said:

Thats very likely true. But the lower coil definitely affects the inductance of the upper coil. How much I can't say, probably not much, but any conductor close to a coil will do that.

Yes, that's certainly true. The bottom line is that there is no way of making a stacked humbucker sound exactly like a single coil - there are too many factors that can't be either eliminated or compensated for without changing something else.

At the end of the day it comes down to whether having a hum-cancelling option is more or less important to you than having the true single-coil sound.

Funkfingers

Looks like I need to gen up again on my Frank Falbo factoids.

Speaking of Falbo, it will be interesting to discover the Fishman Fluence take on a P90.

ICBM

Funkfingers said:

Speaking of Falbo, it will be interesting to discover the Fishman Fluence take on a P90.

Am I the only one who still has to try quite hard not to read this product name as 'Flatulence'?

Funkfingers

That is the usual auto-spelling correction algorithm suggestion.