Video Asylum

Posted by jon_beardy (A) on March 03, 2015 at 16:33:52

Evening, all.

I was just wondering if anyone might be able to give me a few pointers on what might be causing the annoying whistling tone on an AVR-550SD I bought off ebay recently.

It was badly packed (just a couple of layers of thin bubblewrap and then a taped-up plastic bag), so it may have taken a knock in transit. What I'm finding is that on all the analogue inputs (haven't tried the digitals yet), I get an annoying whistling tone whose pitch changes depending on the screen dimmer setting, and which will sometimes stop for a minute or two if I turn the volume up or down slightly. Turning the volume control can also cause a sudden blip upwards in the pitch of the whine.

Some analogue inputs are less affected than others - the CDR/TAPE input isn't as bad as the DVD input, for example. In fact, even with no source plugged into the AVR at all, just switching to the DVD input will get the whistle going.

If some analogue inputs are worse than others, could it perhaps be bad relay contacts, or is there a possibility of a noisy screen or backlight causing the problem? It's a shame, as the amp was cheap (£24), and sounds quite a lot better than I thought it would into a pair of old Mission 771 standmounters, especially when I'm bi-amping with the 5ch/6ch stereo setting (same in-phase signal to L front, L surround and centre, and same for the R channels).

I've tried changing source, interconnects and speaker cables, re-initialising the processor, and turning off my wifi and ethernet-over-mains plug (well, at least the plug downstairs, where the amp is), all to no avail. The amp and source are plugged into an unfiltered block on a 3m extension lead.

The seller claims the amp was working fine when they last used it a week or two ago, but who knows?

Cheers, Jon.