Hi just thought I would give an update…and ponder some questions I had this amp for around 7 years It is cica 2001 vintage… It has always had transformer grumble/buz….which was periodic in the day. This was powered by a std uk ring via a switched socket. I upgraded from std lead to an Evolution 500 RA power cord….this actually helped a little…I then upgraded my mains distribution block…which appeared to help still further. Recently I have changed rooms…and everything is powered off the same ring. However I swapped out the switched socket for..for an unswitched Russ Andrews double socket….and bingo when powered on silent bliss no buzz or hum.
Is this due to the unswitched socket? Or… I have noticed my neighbour’s has thrown out a very old freezer….Or could it be just the repositioning/orientation?? Which could have been the culprit??? Either way I am very happy….
Unless the RA socket has some DC Offset electronics in it, then I cant see this being a cause. What a neighbour does can cause an effect, so lets hope it stays improved (unless your neighbour replaces it with a cheap knock off freezer )
I wondered if the contacts on a switched mains socket were not great….if that influenced hum/buzz…as you would have greater resistance on the power rail compared to the neutral…???
Interesting. My 135s (and before that 250) hummed a lot and often. I dropped in a 500DR a year ago - straight swap, on the same shelf using the same power (except for the 500DR’s Powerline) - and I’ve never heard it hum. Until your post I assumed (maybe naively!) that they the 500 design made it less liable to hum. Brilliant amp anyhow!
Presumably the original switched socket is still in place. Stick an extension lead on it and run the 500 off it and the hum will likely return if that was the culprit. My guess is that it’s not the culprit: the freezer seems more likely, especially if the hum was intermittent.
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