Frustrating and Confusing Amp/speaker Connectivity Problem - Your Expertise Requested

[TubeLover]

I just purchased a replacement 5 channel amplifier to handle part of the needs of my home theater (after the almost twenty year old one developed issues). The amplifier I bought was used, but had just been sent to it's manufacturer for some updates and to ensure a clean bill of health. In fact, the manufacturer shipped it to me, for the seller.

 

When I first connected it up last night and turned it on, the speaker connected to channel four (of the five discrete amplifiers inside it) produced a loud hum and some distortion. I shut everything down and triple checked the connections. The only thing I found that "could" have impacted things was the rca connector of the cable coming from the receiver that I use as a pre-pro was of the locking type, and I loosened it up to ensure maximum contact. When I turned everything back on, there was only the slightest noise from the speaker and it was not audible while watching programming. I sat back and enjoyed a long movie. When I went to shut down the amplifier at the end of the night, as I reached to press the off button, my other finger touched the faceplate of the amplifier about an nch from the switch. That suddenly resulted in the speaker that originally had the problem suddenly making the loud humming and distortion sounds. It was late, at that point, so I put off troubleshooting until today, certain that I had some kind of ground issue.

 

Today, I rechecked all of the connections, reseated the speaker cable wires, and the rca cable, with no change, still the loud hum and noise. I then moved the matching speaker from the "right" side over to channel four (it had been connected to channel five) of the amplifier certain that I would experience the same hum and noise from that speaker, clearly indicating that channel of the amplifier must have a problem. There was, however, not a sound out of the speaker that I had just connected.

 

In the end, because we had friends coming over to watch a movie, I simply took the right and left speakers involved and moved them to my other existing five channel home theater amplifier and everything worked perfectly. I am now at a complete loss as to how to explain what's happened, and have no idea where to go with additional troubleshooting.

 

When I moved the second speaker and it's connectivity over to channel four of the amp, it too should have exhibited the same problems if it was the amplifier that had a problem. When I moved the original problem speaker and it's connectivity over to the other amp, that should have indicated a problem if there was one. Any assistance, suggestions or insight at this point would be greatly appreciated. Thanks.

 

JC