a hint for pup wiring.

[BSAKing]

Basking in the glow of my very successful bridge upgrade on my Joe Pass (unbelievable difference!), I am getting ready to upgrade the wiring and as cash permits the PUPs as well. I ran across this item on another board and I thought it would be beneficial to share it with other members here. I am going to try it as part of the upgrade in mine for sure... O:)/

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Mayby you can help me with my little problem:

I have a gibson es345 ('69) with original PAF humbuckers.

When I put the switch in the middle position the guitar sound out of phase,

which is very annoying.

When I bring down the level of one of the pickups, the sound fattens up,

clearly a phase problem.

I allready had two repairmen check the guitar but none could solve the

problem.

The wiring seems to be OK.

My repairman told me it has to be a problem with the humbuckers.

 

Have you heard of this problem before, and do you think It could be a

problem with the humbuckers?

 

 

...to which this response was sent ...

 

Does the sound fatten up even if you only back either volume control off

just a little bit, like by 10% or so? If so, this is normal for vintage

Gibsons. With both volume controls at maximum the two pickups are wired

directly in parallel and each applies a fairly high load to the other.

As soon as you back either volume control off even just a little you throw

100k or so of resistance between the two pickups which isolates them so

they no longer load each other. The 100k of resistance isn't that

significant to the high impedance amp, so you get almost full volume from

both pickups and the sound is fat.

 

A "cure" for this is to put a 47k resistor between each volume pot and the

pickup switch. This amount of resistance will barely reduce your volume at

all, but there will always be at least 94k of resistance between the

two pickups, preventing them from loading each other.

 

Not all vintage gibsons do this because often the cheap pots they used didn't

go all the way to the end of their electrical travel anyway, leaving a little

resistance between the pickups even at full volume.

 

I'm glad you brought this up, I need to make mention of this "fix" on the

website because I've not seen anyone else note it.

[andylivingston]

That's a nice backing off trick. I had assumed I just wired my pups out of phase with one another since my bridge pickup was wired out of phase with itself at first. There was a mixup in the wire color coding. But hey, I backed off one of the pots, and presto! Fat sound. Thanks.