An unusual problem that merits an unusual solution

This is interesting.

I have a 6 1/2 year Marantz AV-550 that started exhibiting similar behavior, but in the LFE channel. When I change surround modes or mute the output, I get a pop in the LFE.

I thought it might be the subwoofer amp, but the same thing happens with a different amp. Figuring the AV-550 might just be tired, I bought a used AV-560 for $250 but never hooked it up. I guess that tells you how important HT is to me, heheh.

Interesting, makes me wonder if it's something with that (now seemingly ancient) Yamaha AC-3 decoder chip in the AV-550's. Mine may be popping in the LFE channel as well - but I have no sub to hear it with.

Looks like I may have found a solution though - someone emailed me and pointed out the Rothwell in-line RCA attenuators (man I wish I'd known about those when I had my Jolida Tube Amp - it's gain was *way* too high!)

I'm also going to order the Channel Vision 15k Ohm inline resistors as a backup (and for comparison).

I know that this is just a long shot, but have you ever verified that your AC outlets and your gear were properly polarized? Something else to think about is static electricity build up. This time of the year, the dry air and static can cause all kinds of erratic behaviour. We've had reports here of people blowing out digital circuitry just from touching their gear after walking across the carpet i.e. static discharge arcing from the person into the components. Sean
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Just for reference to anyone else who has this problem in the future, I was able to get -6dB attenuators from Parts Express that did the trick nicely.

The "pop" is still there - but it's so much quieter you can barely hear it anymore.

Oddly enough, there's a new sound that's appeared since adding the attenuator - any time the Marantz receives an IR burst - even if the IR is intended for another component - I get a wierd beeping from the same troublesome right surround channel. It sounds sort of like a modem or a fax machine, and is only a second or two long.

Clearly the preamp has issues, but it should get me by until I can afford an Acurus Act-3 or an Outlaw 950. Considering I paid 70 bucks for it on Ebay, I don't really have any right to complain!

Thanks for the suggestion, Sean; no luck however. Our power does seem very dirty and unstable - it's an old house with old wiring in a dense urban neighborhood, and I'm sure that doesn't help. If I could afford a nice power conditioner, I'd get one, but AC stuff is just too expensive. Especially having the quintet of MA-500's - that's 5 outlets right there!

Thanks to everyone for their help in this thread, and over email.