The Performer m1000 has a protection circuit against DC voltage and a limiter against output overload.
If direct current (DC) is detected, the output stage switches off automatically and the Protect LED lights up red.
To protect the output against overdriving, an LDR limiter (light-dependent resistor) is used. Since it works optically, the audio quality is not affected. The Protect LED lights up yellow when the limiter responds.