[sdiy] Grounding check (OT)

[dreichert at sympatico.ca]

Hi all,

This is a bit off topic, but I have a bit of a problem (maybe!)

I've plugged my bass into a used effects processor I just got and when I play I'm feeling a mild sensation in my hands that makes me suspect that something's not properly grounded. 

How can I check this for sure? I tried measuring the strings against the recepticle-ground with a voltmeter, which read nothing (both AC and DC). Am I doing this right or are there better checks?

Cheers,
Dave