I recently picked up a used 2001-2002 era MIM Jazz Deluxe in somewhat poor condition and have been working on it. The only problem I'm having is with the tone. It seemed fine (great, actually) for a day or two but now there is a definite inconsistency that sounds like a light phase shift. I'd say the modulation rate is a few times per second. It seems more pronounced on certain notes but sometimes barely noticeable. Doesn't seem to matter where the pan knob is set at (neck or bridge pup). Strings are brand new and the battery is fine (I replaced it). I think this bass has the Suhr pups. I've done some searching and found nothing about this kind of issue. I have very limited electrical knowledge but can do basic soldering. Before I take this to a shop does anyone have advice on what to look for? Thanks in advance for any help you might be able to offer.
The first thing I do in this situation is try the bass with different strings. Even an old set. I am familiar with this model and if indeed the original noiseless pickups and Fender preamp were absolutely aweful, I doubt they are responsible for what you describe. If they are not the original pickups (Fender Noiseless pickups), it is possible someone made a mistake installing the after-market pickups and installed them out of phase but in that case, the problem would disappear if you use only 1 pickup. Usually a good tech would debug that in a minute.
Take the strings off. See if they are twisted. Strings that were put on with a lateral twist (caused often by turning the strings round and round the post by hand rather than letting the post turn and pull the string in) can end up sounding weird like that. Happened to me before.
Thanks for these suggestions. I'll try a different set of strings tonight. FYI I have Warwick EMP coated stainless strings on the bass now. I did install them by letting the post pull the string in.
Aside from a twisted string, the other cause might be pickup height. If the pups are too close to the strings this can cause a chorus-like effect due to too strong of a magnetic pull on the strings.
Correct, I totally forgot to point out this possibility and if it happens on more than one string, that would be the most likely cause, if it happens only with one string then is it is string issue.
I'll try Indeed this seems to have been the problem. I hadn't adjusted the pickups and they were too high. Thanks so much for your help!