Audio Amplifier with Problems

A few months while scrutinising a great design for a pulse-width modulated audio amplifier with a 2x100 W power rating and a very small enclosure, we were immediately very enthusiastic and thought this design would certainly deserve a place in Elektor Electronics. So our resident audio designer was going to put the circuit through its paces. The results were most unusual and this led to an extensive investigation of what was wrong with the amplifier. Was there a fault in the design or was something else the matter? This turned out to be quite a quest…