Possible causes include an input level that is too high and an output level that is too high.

Adjust the [TRIM] control (input) or the LEVEL control (output) so that +14 on the level meter does not light.

If the sound is distorted even when the input and output levels are adjusted, you may be exceeding the power amplifier's maximum allowable input level. Lower the output level to an appropriate level using the [MASTER ATT] control on the rear panel.

The level is lowered to 1/2 at -6 dB, to 1/4 at -12 dB.

This setting is not associated with the master level meter.

The same is true for ZONE OUT.