Edit: FIXED!!! See Post # 13
I'm skipping the NBD thread and going right to the "Help!" thread.
I've just taken possession as the 3rd owner of an inexpensive project bass, a 2004 MIM Deluxe P-Bass Special that's got an AWFUL case of VVT syndrome.
When solo'd both pickups sound fine -- nice P tones when the J is off, nice J tones when the P is off, but play them together and now the problems start.
The log taper volume pots don't seem to do anything during the first 3/4 of their rotation -- it sounds like the volume doesn't come up at all. Then during the final 1/4 turn of their rotation the volume comes up really loud, really fast. In other words, only the final 1/4 rotation of the pots is at all useful.
The biggest problem that in the last part of the rotation, maybe the last 5% to 10%, there's a huge interaction that takes place between the pups -- while the P+J blended tone was nice and fat at around 80-90% of the rotation, as soon as one of them hits 90%-100% rotation the tone becomes very thin and weak. The bass is just not useful with either one of the volume pots wide open.
I just finished pulling the pups to see what's inside. The bass came from the factory as a passive precision with P+J pickups and a VVT setup. The original owner cobbled the bass up a bit, upgrading the J-bridge pup and attempting to convert it to an active setup, but then backpedalled into putting it back to a passive wiring configuration. Looking at the wiring setup, the bass has been restored to a normal VVT wiring setup.
The specs for the bass say that it's supposed to have the following pickup configuration:
1 Standard Alnico Split Single-Coil Precision Bass Pickup (Mid),
1 Vintage Special Single-Coil Jazz Bass Pickup (Bridge)
Pulling the pickups, here's what I've found:
P-pickup: Bobbin has 048614 embossed into the plastic bobbin, with the number 96004 written on the bobbin in white china marker.
J-Pickup: Has a small sticker with the following numbers on it: IGC77 SJB1B 0375
I have not had any luck finding out that the handwritten "96004" number means on the P-pup. 048614 seems to be a generic bobbin number. I'm thinking that the bass has the original P-pickup, but that the previous owner had replaced the original J-pickup with a Seymour Duncan JB-1 bridge pickup.
By themselves each pickup sounds fine, but played together the pickups are WAY too interactive. When turning up the volumes all the way, it seems as if the inductances are way too interactive with each other and the frequency response suffers horribly.
Another problem is that the tone control has to be left in the rolled-off position, otherwise the sound is just way too bright. I wonder if there's been a cap change. I'll have to check on that. All of the pots are 250k log taper.
I'm thinking that I'm probably going to have to re-scale the tone control to tame the roll-off a bit. As it sounds right now, the tone is great when rolled off, great when cracked open to maybe 25%, but way to shrill from 25% to 100% open. I'd prefer to re-scale the pot + cap combination so that a new control mimics the range that the current setup offers when the tone knob is rolled off at 0% open to 25% open.
I'm looking for advice in how to take care of the interaction problem. One thought might be to go to a VBT setup, but a proper lin-lin VBT blend pot uses 100% + linear tapers on each side of the midpoint, and these pickups have horrible interaction if either one is set to 100%. I'd really like to find a solution that doesn't involve limiting my choices to P-only vs. J-only, but that's the way that the bass works best right now.