Official Luthiers Forum!

I need some help. This is a wiring diagram that I put together for a Jazz bass mod - providing seperate tone and volume for each pickup, as well as a series/parallel switch. It may seem like a lot, but it would allow me to dial in a specific tone for hamonic/ chordal playing. Regardless, upon its first implementation, the idea is there, but there are significant quirks. They include: When in parallel mode, the volumes overlap each other and one acts as primary, the other acts as a secondary tone form; This also happens with the tone, but in a different form. I know things like that should happen when switched to series, but the parallel just is not quite working.

I believe that I vastly oversimplified the circuit, and am not wondering if I could even do what I want to do.

Any thoughts would be hugely appreciated.

Thanks so much in advance,
Stephen

_________________
www.ziegenfussguitars.com

Most likely you have the inputs and outputs of the volumes pots wired wrong. For single volume pot, the pickup should come in at the tap on the left side (as you look at the underside of the pot and go out from the center tap, with the right side tap grounded. With two volume pots in parallel, go in from the pickup on the center tap, and out from the left side tap. You don't use the right side tap in this configuration, but it's a good idea to ground it to the pot anyway. The first configuration is preferable with one volume control, since when volume is less than full, the amp is looking partially at ground and partially at the signal, which lowers noise. The second configuration treats the pot as a rheostat rather than a potentiometer, and can have a bit higher noise. But if you use the first configuration with two pickups in parallel, turning the volume down on one will also turn it down on the other.

Oh, sheesh. That Guest post above was me. The automatic login doesn't work. That happens to me on some other forums like 13th Fret. Maybe because I'm on a Mac? Anyway, the attachment didn't display when I was a guest. It's hard to see, but I think my above comment applies.

[edit] OK, I enlarged the drawing. The problem is as I suspected. When you switch the pickup input to the center tap of the volume pot, switch the connection to the tone control to that tap, too, so the tone control is isolated from the other pickup. Even after you make these changes, you may get some cross-control of the fingerboard pickup by the bridge pickup's pot because it is 250K (which may not be enough to totally close off the output from ground when the fingerboard pu is looking back into it in the parallel arrangement). If so, go to 500K on the bridge pickup volume and tone pots. You gain isolation but you lose some fine control with the 500K pots.

_________________
Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

if you click on it, it will get bigger.

But thanks for your input. I need to sit down after work and draw out what you said (I am a mechanical engineer, so I am entirely graphical ).
Thanks so much,
Stephen

_________________
www.ziegenfussguitars.com

Thanks so much Howard!

_________________
www.ziegenfussguitars.com