The proximity was just about a hum test, not a legitimate playing position. Though, you know what it's like to be a bass player, the lead guitar and singer take 90% of the stage that doesn't have drums on it and we usually get about six square feet of floor space. The rehearsal space hasn't given me any noise problems at all, further evidence that it was an environmental thing when I had noise.
The night I had problems, I had about 8' of space from my rig to my mic. It didn't matter where I was in that space, or even another few feet off to the side. I got the same higher frequency noise either with the Excel or with the Zon if the pickup blend was all the way off center. If I centered the blend, it was quiet.
Like I said, the one big difference is that I didn't have my good power strip with me that night. I know there was an LED light hooked into the same circuit, and possibly a small powered PA monitor. I'll look into the wobble when I get a chance and I won't forget the power strip, so we'll see what I get. I get set up early enough to run a check and carry a backup, so it's never the end of the world if one thing goes wrong.
I am leaning toward the power feed being the issue, but I was surprised that the Excel acted similarly to the Zon in one-single-coil-pickup mode. I would have expected it to mirror the Zon in both-pickups-full-on mode.
Also, we've got 2-3 gigs a month for the foreseeable future, so there will never be a convenient time to ship parts across the country. Fortunately, I'm in the too-many-basses club, so time can be made if it seems the right thing to do.
We won't be back in that problem room until June, so I will monitor things in the meantime and if it's still a problem then with the good power strip in place, I'll think about pulling the guts and sending them west.
-bob