This is a follow up to a thread I started a while back asking why my 400w bass head has can easily overpower PA systems rated as high as 4,000 watts. There were a lot of theories floating around but the one I took on board was that my bass head is only amplifying one instrument, but the PA has to deal with many. Suddenly I'm not so sure. On the weekend I was presented with a situation which is unusual here in Oz. The club we were playing at had installed a medium sized PA for the bands to use, but do not supply anyone to operate it. I've done my fair share of PA work so I was "volunteered" to operate it while I play. I turned up really early to get in a decent sound check. Since I was the only one there i decided to put the theory to the test and run a back to back "shoot-out". I wanted to see which was louder, my 400w head, or a PA with only one instrument to deal with. My amp killed it! It wasn't even close! The PA, on each side, had a single EV 18" sub ,(Crossover point was 120hz.) plus 2 EV mid-high cabs with a 15" and a horn. The Amps were Australian Monitor 900w a side for the mid highs, 1,200w a side for the subs (that's a 4,200w PA). Sorry to do this to you all again but I'm really back to square one. Maybe my 400w amp is freakishly loud giant killer?