I've got a Les paul jr. project that is still in the hypothetical stage and the main thing I wanted was to be able to have a high ouput pickup that could drive the amp and a bass cut. The pickup I wanted to put in is a jb and they can tend to be a little bright. I was wondering if it would be a good idea to add a very small cap to the volume to give it more versatility. What I wanted to know is if any of y'all have tried this and if it is a good idea or not, as well as what cap to use.
So are you wanting a treble-bleed cap or a treble-shunt cap? Treble-bleed will retain highs (but only when the volume is rolled down) and treble-shunt will cut some of the highest frequencies out of the signal. The one you want determines how it'll be wired (idk if you already knew that or not). I've tried both and they work well enough. The cap value is a personal preference but I'd start with 1nF to 2.2nF. Probably wouldn't want to go higher than that. As for whether it's a good idea, that depends on how you like it.
Treble-shunt is what I was looking for, but it really depends on how bright it ends up being.
If it's just a one-pickup setup then just solder the cap across the volume pot's 3rd lug and ground.