I'm SHOCKED literally .

I put a couple of new components in, and generally shuffled things around in my system last night - and after listening for a couple of hours today - got SERIOUSLY zapped (it was audible) as I touched the Volume knob on the preamp to turn it down. There was some kind of charge build up, and it took a while to drain it all down - I had to (gingerly) touch the knob a couple more times and then hold it until the charge was drained off. My finger still hurts!

This has never happened before - so it's not static from my rug or something. I'll be doing some careful testing tonight, but in the meantime - Any ideas what could cause this???

Possible explanatory variables:

---The "new" items were the preamp (tube) itself, the processor which connects through the Pre's Tape loop, and a Granite Audio power cord with toroidal noise filters at each end connecting the Pre to a surge protector (temporarily). The surge protector has been in use elsewhere with no trouble.

---The new processor is a two prong plug - Polarity?

Tonight I will try running a couple of hours with the processor unplugged and the Tape Monitor OFF to see if I have the same problem. Or if any other equipment has the charge buildup.

Any ideas? Is there a plausible explanation without there being an actual equipment problem?