Sequential circuits samplers

>>periodically, it seems as if some voices are a bit softer/scratchier
than others...is this a sign that the voices are dying?<<

I'm not sure what you mean by "scratchier"... the 8 voices in the p2k
are analogue, so there will be a little variation with age,
temperature & amongst themselves when playing similar sounds. the
curtis chips do fail from time-to-time, but they usually stop suddenly
rather than die slowly. more likely some of the passive components
around them & the output stages are starting to go bad. but unless
it's crackling all the time, I'd leave it for now.

>>also, i have my prophet plugged into a furman power conditioner.
because the on/off switch is in back, i leave it on and turn the
sampler on when i turn on the furman. is there any reason to think
that this may harm the sampler in any way?<<

I've done exactly the same since 1990 & my sampler's fine.

duncan.