3 pickup wiring help

[adamrobertt]

Hi guys. I’m trying to wire a 3 humbucker guitar - the client wants a blend control for the bridge and neck, a master volume, and a separate volume for the middle pickup.

No matter how I wire it, both the master volume and the middle volume both work as master volumes.

Anyone have any experience trying to do this?

[alexpigment]

I’m presuming the master volume also controls the volume of the middle pickup (i.e. if the master is at 0, the middle is also at zero regardless of where you set that volume). Correct?

If so, I believe you would just go from the out of the middle volume pot to the same lug of the master volume that you’re coming into from the other two pickups. Since you said there’s a blender for those, I think that means the out from the blender pot and the out from the middle volume pot go to the same input lug on the master volume.

Then again, this is all just coming from my head, so maybe I’m missing an important detail or grossly oversimplifying something that isn’t simple

[alexpigment]

I thought a bit more about this on the way home, and I'm wondering if what you're experiencing is similar to how a Les Paul is silent in the middle position if *either pickup* is turned down to zero. This has to do with them being wired in parallel and the grounding of one pot affecting the other. The wiring scheme I had in my head may or may not run into this - I'm not Jedi level enough to say definitively without testing.

I know the whole "middle pickup volume" thing has been done a thousand times, but with a cursory search I couldn't find any wiring diagrams where the master volume has any control over the middle pickup - maybe there's a reason for that. It may be helpful to look at this Brent Mason tele diagram, which shows that the middle pickup volume only joins up with the other circuit at the hot lug of the output jack itself:



Again, there could be a technical limitation that makes it difficult to do otherwise.

[Futuron]

(Assuming you do want the master volume to affect all 3, and not just the 2 blended pickups) Try the above diagram with a few alterations:

-No need for the tone controls (unless you are using one after all)
-Change '3-way switch' to 'blend pot' (straight-forward black box replacement)
-Probably use 500k resistors for humbuckers
-Instead of having the thick grey wire go from the outer lug of 'middle volume pot' to 'output jack', go to outer lug of 'master volume pot'. (ie join it with the black wire that's from 'blend pot'.) Making sure that the hot from the middle pickup goes to the sweeper as is shown - important point.

The arrangement of the volume pots' wires can determine whether they affect each other or not

[alexpigment]

(Assuming you do want the master volume to affect all 3, and not just the 2 blended pickups) Try the above diagram with a few alterations:

-No need for the tone controls (unless you are using one after all)
-Change '3-way switch' to 'blend pot' (straight-forward black box replacement)
-Probably use 500k resistors for humbuckers
-Instead of having the thick grey wire go from the outer lug of 'middle volume pot' to 'output jack', go to outer lug of 'master volume pot'. (ie join it with the black wire that's from 'blend pot'.) Making sure that the hot from the middle pickup goes to the sweeper as is shown - important point.

The arrangement of the volume pots' wires can determine whether they affect each other or not

What you described is the wiring scheme I was thinking of as well. Essentially, make the blend pot and middle volume pot go in parallel at the master volume. However, I'm wondering if that's where the OP was having the problems he described. Do you think it would have an effect of the middle volume at zero causing the master volume to go to zero as well (like the Les Paul middle position scenario)?

[adamrobertt]

Thanks for the replies guys!

I’ve tried both running the master directly to the jack, and I have tried summing the blend and middle where Futuron suggested - both still did the same “Les Paul Middle” thing.

[alexpigment]

Maybe this will be helpful:

https://forum.gibson.com/topic/52411-3- ... -know-why/

This is a post on how to avoid the Les Paul middle volume thing. For a Les Paul, it's says on each volume pot to switch the wire that comes from the pickup with the one that goes to the switch. In your case, it would mean on the master volume swapping the wire coming from the blender pot with the one that goes to the output jack (I think). The same logic will probably need to apply to the middle volume pot as well. Anyway, worth giving that a read and seeing if it inspires any 'a-ha' moments. Otherwise, it sounds like you tried the two methods that make logical sense, so it's all beyond my area of experience at this point.

If it helps, here's a similar post on Stewmac's site about Jazz bass V/V/T wiring (which doesn't suffer from the problem):

https://www.stewmac.com/video-and-ideas ... jazz-bass/

[Sweetfinger]

You wire the neck and middle as a classic "blend/balance" circuit with a dual ganged pot. On the volume for the middle, connect the pickup lead to the middle lug and the outside lug to the master volume, along with the signal wire from the blend/balance pot.

[adamrobertt]

Ended up figuring this out - wiring it like a Jazz bass with an extra knob worked. I had tried this previously but something else must have been messed up, causing me to believe the wiring didn't work. Ended up just ripping out and starting over and it worked. Oh well.

[Futuron]

That's good (in the end at least, anyway), I put effectively the suggested circuit (but with the master volume lugs swapped around to be the same order as the other one) together today to check, and no shenanigans with the multimeter readings that I could see.