Perhaps owners think they will be charged more for stupidity. You'd think it
was like the doctor-patient consultation.
Perhaps just a chance thing or maybe he plugged a speaker lead in one of the
amp 1/4 inch inputs.
Input to a SMD JRC/ NJM4560 stuck at 7V and its output at +ve rail, 10K in
the line not enough to limit whatever went in there, perhaps high dV/dt,
giving him the benefit of the doubt