Electronics control question

[RickRocks]

I'm wanting to rewire my Spector Legend 5 classic (w EMG-HZ p/ups) to have a pickup blend knob and a master volume instead of two volumes.
I was looking up blend knobs online and how do I know which one i need? There was a 250k, 500k, ect. How do I know which will work? And will I need to get a different volume pot or will one of the stock ones work?
I'm also wanting to do this on a passive mexican jazz bass with US pickups. So info on that would be good too.

[Cadfael]

Do you have the "TonePump Jr" on board?

I have both wiring diagrams in my compendium!
With two volume and with Master Volume + Balance ...
See schematic 1.9.71 (page 235 at the moment) and 1.9.75 (page 237 at the moment)
http://161589.homepagemodules.de/t29...-E-Baesse.html

Scroll down, click "Bassschaltungen387.pdf", wait until it has downloaded (5.9 MB) and save the file on your hard disk. New version with 15 pages more will be uploaded soon.
The compedium is in German but you will understand! Or just look for the differences in the schematics ...

I also have the solution for the "BP-4" preamp in it!!!

Short: You need a 500k balance pot (for both basses) and can use one of the oled pots as master volume. In 2.1.21 (page 247 at the moment) you find the Jazz Bass solution ...

[RickRocks]

Thank you for your reply! Yes it does have the tone pump jr, i want to upgrade to an aguilar obp-2 eventually.
I'll probably take it to a guitar shop to have it installed as my soldering skills are not where id like them to be. I just wanted to get the parts so they don't gouge me on the price.
Will the 500k be what I also need for the jazz bass?

[Cadfael]

The value of the Master volume pot depends if you put it before or behind the preamp (next to pickups or jack). With 500k you can't go wrong when it it between preamp and pickups (like in the original Spector preamp solution).

The Balance has to be between PUs and preamp. So, it "must" be a 500k pot.

Theoretically you you make experiments with a 250k or 500k balance pot in the Jazz Bass.
But as the Balance Pot is in series with the Master volume, I would prefer (try first) a 500k Balance and a 250k Master volume pot.