First off to the OP, you can't implement such 'protection', it isn't that bad when an
amplifier clips. The top and bottom of the waveform literally get clipped, and until you
get into gross clipping that is audible, the setbacks are not noticable.
You want PEAK transients to get through, and often enough, these peak transients clip the
power supply.
A clipping circuit is usually a indicator (LED) telling you that the amplifier is
clipping. Protection on the output is another story. You don't want it to unlatch the
outputs like that, if there is hardly any protection, your amp may not even have open load
protection!?!?
Put the amp on a circuit capable of running the amp at full power, apply a test signal
1khz lets say, then turn up the gain and observe the output on a scope while it is
connected to a resistor load capable of dissapating the power. Once you see the waveform
clip, you can set this as a reference lets say to a LED VU meter (ie: Dorrough Loudness
Monitor Type 40-A).
Or you can monitor the voltage on the output, and then design a circuit to light a LED
when the AC V gets to that point, however, this won't be entirely accurate.
check out
www.ramaudio.com and see how a professional amplifier mutes the input when a
total short across the output occurs, and how it actually eliminates clipping without
loosing the peak transients from coming through.
hope that helps.