Site maintenance in progress, some wonkiness may ensue. Thanks for your patience.
QSC, If I recall correctly, is who Behringer had design and build the EP1500 and EP2500.
Behringer,QSC and ALTO uses almost the same schematic,and exactly the same chassis except the front panel. Must be made at the same factory in China somewhere.Repair tip:The pins on the driver transistors often break mecanically.lydmann