Probably a really, really dumb question...

...but I don't do electronics. :( So was wondering if anyone could make sense of this for me...please...

I have two pick-ups with a volume control each, no selector switch or master volume and the electrics are passive.
If I turn one pick-up up the output goes from nothing to full volume, however, I can then turn the other up to change my tone but the overall volume doesn't change (which is a good thing, as far as setting levels and the like goes, I'm not complaining) why?!!!! The more I think about it the more it bakes my noodle, please explain!


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Sorry Tim i'm waiting for Bass to nudge in on this one..

Yeah, it's too technical for me too!

And I thought you just didn't love me anymore... :(

It's all these threads (2 of them) about designing-your-own getting me thinking, but I don't get the internals.

i would have a good idea if the project were in front of me.
How many wires on the pickup? and how many tags on the vol pots?
no selector going to a standard mono jack?

Funnily enough I just happen to be sat here with the back-plate off and you may have a point:

Each pup has a black and a red coming from it but the neck pup red goes to the neck volume pot but the black goes to the bridge volume pot. The bridge pup black and red go to the bridge pot. Then, both to the tone then red to the jack and black to the bridge (earth?) although now I look at it all the blacks may be earth (as mostly soldered to outside of pots not contacts), which doesn't help, whats wrong with yellow and green?!

I give up for tonight but thanks so far...


Oh great, how did I become the resident Guitarsite solder-monkey :?: :lol:

OK, the thing to remember is that your instrument supplies a feeble DC to the amp. Alternating current doesn't come into it so that's why you don't see green/yellow wiring. As you've worked out, Tim, red is the "hot" and black is the ground/earth. Thank goodness you don't have a genyooine humbucker because that would complicate things. It reads like the standard Jazz bass vol-vol-tone setup on your bass. It doesn't matter if you have a PJ, the stack works the same. Have a look at to see how it goes.

As you say, the black wires can be soldered onto the body of the pots, thence onto the bridge - the biggest single lump of metal, used as the ground/earth. From what I've read, it sounds like you have a perfectly normal setup for neckvol, bridgevol, toneforboth and it's all grounded to the bridge.

But it's late for me, too and I could have got it wrong :) When you fiddle with your knob(s), is it pleasurable and does what you'd expect?

Thanks 1BL, that does make sense now I'm awake (and sober helps to!) I'll check out that site. In reference to my original query about levels I presume there is a difference but this is negligable due to the diddy DC?...I'll go read the site :lol:

Thanks again, I'm basically trying to figure how few controls I could get on a (pie in the sky) custom-build.


Aah, I get what you're saying, I thought you had some problem with your bass. You mean "how come the volume doesn't double when I turn up the other pickup?" Now I get it and, d'ya know, I've never thought about it. It's far too late in the night to run it through my head but forget that site-link. The hyphenated URL leads to a pile of poo. Here's the proper site that has all major wirings.

I'll have a thunk about it.
ps, on a two-pup bass your minimum controls are either the Jazz VVT, a VT with a DPDT on-on-on switch or a MV/pan/tone. Unless, like EVH, you drop the tone control altogether (cf glw's post). If you don't mind stacked pots and want versatility you could use something like EMG's active BTC which has bass and treble cut/boost on a stacked pot. Combine that with a stacked vol/vol or vol/pan for a two-knobhole setup.

I knew you could sort it Bass. :lol:

Not really, I'm very ropey on the theory myself and had to have a web-rummage. Yes, the output is feeble (a pup's output voltage ranges from 0.1 to 1V) but, of course, an alternating current is induced in the coil. When the string waves around through the magnetic field, an alternating current would oppose it. Combination of raw ignorance and too tired to think it through. Apologies.

As for the other bit; again this is surmising from my hotch-potch of garnered electricals - not the word of a trained sparkmeister. I suspect that you get only minimal changes in output level when flicking from one pup to both because the two pups are wired together in parallel. If they were wired in series, then you would get a noticeable increase in output level as you switch to the combined. I think that's right anyway.

As you already know, some pups have a higher output than others but this can also be necessary to counteract the variation in the way strings move the further you go away from the bridge. If anyone's interested in a quick read that's been written so as not to crush your head in, click here at Helmuth Lemme's page:

I know a few fiveheads that would argue with some of the points, but it helped get me thinking straighter.

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