We use d-45 amps in a post production facility. The amp intermittently would start to distort the audio until unplugging and re-plugging the xlr connectors on both channels. Recently the amp consistently distorts the audio like it is being over driven. The LEDs are always green and the pots are set at about 50% of capacity. It's being fed by a mackie mixer, when listened to by itself sounds great. It's out of warranty so any ideas would be appreciated.