I play all my instruments thru a K&K Pure pre-amp. Has a single 1/4" input (from the instrument) and a single 1/4" output to PA, amp, whatever I use. Powered with a 9 VDC battery. Does not have a bypass function. Been using this for over a year. Had a couple of St Pat's gigs, so I changed out the battery (usually do that every month anyway). At a local gig on Thursday, where I've often played before thru this exact rig and the house PA, I could get no sound (the PA was getting no signal). Swapped chords, etc., nothing. Plugged straight into the same PA channel with no preamp or DI and it worked; just didn't sound as good (impedance mismatch). The next day at home I was checking everything out using my old Peavey 130. Everything worked fine (cords, pre-amp, amp, instrument pickups, all good). Took instruments, preamp cords and Peavey to play first gig last night (playing thru my amp and not a PA). No problems on both mandolin and fiddle. Go to the next gig where I'm playing with my pre-amp thru a different house PA (left the Peavey amp in the truck); have the same problem as I had on Thursday, plus now when I plug straight in I still get no sound thru the PA. I use good quality mono 1/4" cords. In both cases (Thursday and last night) this was not an intermittent problem; the PA was getting no signal. I should have paid more attention to the brand/model of PA as that would be good info for troubleshooting. Anyone have a similar issue ever come up? Thanks.