Tone buzz w/one bass but not the other - will active help?

[cnjvh]

Have a Spector NS2000/Q5 which buzzes like mad under dimmer lights.

I don't think this is a gounding problem as its not a hum that changes based on touching/not touching things but a buzz that comes and goes based on tone controls and facing different directions.

The pickups in this bass are passive EMG-40HZ's with the BTS preamp.

Now, I have another bass with active EMG P/J style pickups and no preamp (pickups wired through volume and cut-only tone controls and then right to the jack) and this bass is completely quiet in the same conditions.

So is the buzz:

1. Because the good bass is active and the other not
2. Because the good bass has no preamp and the other does
3. Because the good bass is P/J style and the other soapbars?

What is the likelyhood that changing to active CS/DC's from the passive HZ's will stop the buzz?

Thanks!!

[Warpeg]

Your passive pickups have a lower output than active pickups. However, the "noise floor" remains basically the same for passive and active. Being that the passive pickups are lower in output, they will appear to have more noise than active pickups. There's a bit more to it than that, but you get the idea. Anyway, the BTS preamp is amplifying that passive signal with the noise. Voila--louder noise. If you take out the passive pickups and put in active pickups, it will probably get rid of the noise. Have you tried shielding the pickup cavities? Do you know if the pickup wires are twisted pair, separate conductor or shielded dual conductor?

[cnjvh]

Thank you for you reply. I have not tried shielding the cavity as the bass that does not buzz is completely unshielded.

The pickup wires are not twisted - just a set of wires coming from the pickups and terminated with the EMG quick connect plug which attaches to the preamp.

I have a set of active EMG dc/cs on order so I'll see it that fixes the problem (Spector customer service also felt that active pups would correct this issue).

If not, I'll go for the copper tape shielding. Easiest solution first, right?

;-)