This may be of value to some of you. It's from Lord Valve's latest power amp catalog. OF SPECIAL INTEREST TO BASS PLAYERS:It has come to my attention that many of you are tryingto use the QSC PLX-series amps with preamps which operateat less than standard +4 line level; among these are theTrace Elliot models, some SansAmp DI-type products, Aguilars, Line 6 Bass PODS, etc. Nearly all of these devices operate at a level somewhere between -10 and +4; problems occur because (especially with the higher-powered amps in thePLX series) the preamp can't drive the amp to full power. I now offer a mod to the input stage of any PLX amp which*doubles* the input sensitivity, ensuring full power output with preamps or other devices which operate at less than industry-standard output levels. This mod is reversible, and does not affect your warranty, as I am a QSC-authorizedwarranty technician.