When using multiple stereo amplifiers, you are typically going to have a left and right channel. These channels are in charge of the audio being produced on each side of the stereo connection. If, for whatever reason, the left channel is producing distorted audio signals, you will need to troubleshoot the equipment and determine what exactly is causing the problem. If you don't, the distorted audio will continue.
Turn down the volume on your sound system. If the audio is too high, you may damage the amps, which will result in permanently distorted audio.
Look over the wire or cable connection running from the left channel amp to your sound system. If the cable/wire is not inserted completely into both the amp and the surround receiver, the compete audio signal does not reach the connected speaker, resulting in distorted audio.
Adjust the "Pan" on the surround system until it is at "0." If the pan is turned either to the left or to the right, the produced audio becomes uneven, causing one of the hooked-up speakers to produce more audio then the opposite speaker.
Disconnect the left channel amp and hook up a different speaker. If the second speaker functions correctly, you will known you just have a damaged left amp channel.