Hi, Slammer.
Hmmm. I haven't played her recently, so I can't answer directly. Last time I _did_ play her electrically was about 2 years ago and I don't recall any intrusive noise from the electronics. But that was a while back, and it was at fairly low volume (not stage volume).
With a '76, there'd be two noisy pickup issues to worry about: microphonics (or any other degradation from the pickup manufacturing process) or the Series I Upgrade kind of noise, where the relatively ancient electronics weren't designed to deal with the rigors of our modern electromagnetic environment.
Big Red has an original PF-6 card, and has never had an upgrade. I'll see if I can get up to Santa Rosa in the next few days and check that out.
nic