03-12-2016, 12:15 AM
Exactly. Anything above audio frequency can't be heard, but if large in amplitude could potentially overload the amplifier, causing audible artefacts. So good practice is to filter out. I used the term 'ultrasonic' meaning above AF, but I'd intended this as frequencies 20kHz to infinity - which would include surface scratches and clicks harmonic content, Broadcast band pick-up, mobile phone pick-up, everything! And radio signals can and do get demodulates, particularly in badly-designed solid state units, so well worth filtering out before that happens!
