John Buchanan Posted October 5, 2011 Report Share Posted October 5, 2011 (edited) I've got a Studer amp to keep my Stax menagerie under control via the SRD-7 Spritzer. It has always had quite marked mechanical hum when run at 240V (Australia's mains voltage). I have a 240 -> 110V transformer and the Studer is able to be configured to almost any possible mains voltage via a rotary switch and with a change of fuse. Did that. NO FREAKIN' HUM! $2.50 for 2 new fuses! Love it. Edited October 5, 2011 by John Buchanan Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 5, 2011 Report Share Posted October 5, 2011 That means you likely have a larger problem. I'd guess you have a significant DC component on your AC lines. Quote Link to comment Share on other sites More sharing options...
John Buchanan Posted October 5, 2011 Author Report Share Posted October 5, 2011 DC on the mains? How does that get sorted out? Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 5, 2011 Report Share Posted October 5, 2011 DC on the mains? How does that get sorted out? That's one possibility, there could be others. Just letting you know that it's likely not the amp's transformer, but poor filtering on the amp PSU combined with some really bad mains voltage. Quote Link to comment Share on other sites More sharing options...
John Buchanan Posted October 7, 2011 Author Report Share Posted October 7, 2011 I thought it may be a mains related problem, as the hum was not consistent. Quote Link to comment Share on other sites More sharing options...
Duggeh Posted October 7, 2011 Report Share Posted October 7, 2011 If you've got a hum on 240, the mains plug may be wired the wrong way round. Quote Link to comment Share on other sites More sharing options...
gurubhai Posted October 7, 2011 Report Share Posted October 7, 2011 I would get hum on my amp when the mains voltage would drop below 200V(and that happened often during the summers). The issue was that the LM317 would drop out of regulation, fixed it by getting a bigger transformer. Quote Link to comment Share on other sites More sharing options...
John Buchanan Posted October 7, 2011 Author Report Share Posted October 7, 2011 If you've got a hum on 240, the mains plug may be wired the wrong way round. Hmmmmm interesting thought - might try another IEC cable and see if that makes a difference. Quote Link to comment Share on other sites More sharing options...
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