I just pulled my Kramer XL7 (DiMarzio high-output p'ups, 9v preamp) out of storage, gave it a fresh battery, and started to play. I kept feeling little electric shocks as I played! Very subtle little shocks, but enough to make me wonder what's up. So I got out the DMM, and found that there is about 280 mV ac across ground. The preamp grounds to the bridge (and the strings, etc.). It doesn't read anything for VDC. And I tried the same measurements on my other bass (Ibanez MC980), also with a 9v preamp, plugged into the same amp (PJ Briefcase) with the same cable, and did NOT get any ac or DC reading across ground. Any ideas? Is there something obvious I should look for, or certain test points I should be sure to read? Thread links I may have missed? FWIW, I cannot hear any extraneous noises like hum or buzz or static; in fact it sounds perfect. ??? Thanks!