Thumping Subwoofer

This problem seems to have appeared out of nowhere. I haven't changed anything in my setup. My Paradigm Servo subwoofer has decided to make a thump sound every time I switch (with or without remote) to a different input source on my Yamaha RX V2200 receiver. This also happens on DVD menus and during playback when the DVD does a layer change. If I turn on the <Mute>, there is no thumping if I change the input source on the receiver itself. However, if I use the remote control, it thumps. I think this happens because the remote automatically turns off the <Mute> when a different source is selected, therefore sending the noise to the subwoofer. The thump also occurs when I turn on/off the <Mute>. Not so much when I turn it off but I can still hear a soft thump. Only the subwoofer thumps. There is no thump coming from the other speakers.

I've checked all the connections and re-tighten them but the problem persists. I read on an Internet forum that I could fix the problem by forcing the input settings on the receiver to "Digital" or "Analog" for each input source. Apparently, if the receiver is set to "Auto" detect the source, it causes the thumping / popping on the subwoofer / speakers. I checked the settings on my receiver but the only choices the Yamaha has are "Auto", "DTS", and "Analog". In any case, I tried all different combinations but no change.

There have also been some references on some forums that it could be a "ground loop" problem between the receiver and the subwoofer. Some resolved this problem by using an AC adapter that allows a 3 prong grounded plug to connect to a 2 prong outlet or by using a ground loop isolator. I don't think this would help my situation because my subwoofer power cable already has two prongs and there is no a buzzing / humming noise emitted from the subwoofer (assuming that no buzzing / humming means no grounding problem).

One post I read had an identical problem and his solution turned out to be a new cable. To checkout this possibility, I removed ALL the connections from the receiver and then connected the subwoofer with a new cable. In fact, I also moved the subwoofer across the room to reduce the chances of it being on the same power circuit as the receiver. I still got the switching problem.

I suspect this means that the receiver is indeed the culprit. Whether it is actually a transistor or something else on the "muting circuit", I don't know.

One last item I checked was the switch setting on the back of the subwoofer. It was set to "Auto on/off", so I changed it to "Always on". It's still thumped.



Please let me know what you think and thank you for your help. I really need to get this booger fixed.