Switch input connection pairs and if the 'fault' doesn't changes from one channel to the other it is almost certainly an amplifier or output fault. Likewise switching the speakers. If after swapping the speaker connections the fault changes to the other speaker it is an amplifier fault. If not a speaker fault.
Answers & Comments
Switch input connection pairs and if the 'fault' doesn't changes from one channel to the other it is almost certainly an amplifier or output fault.
Likewise switching the speakers. If after swapping the speaker connections the fault changes to the other speaker it is an amplifier fault. If not a speaker fault.