DC blocker seems to improve sound quality

bthogan

So I had a not-unheard-of problem with the toroidal transformer in my McCormack DNA-1 amplifier - transformer hum. Classic symptoms: hum was intermittent, tended to intensify at certain times of day/night, etc. Looked around for a solution...there are a few of them, some are kind of expensive...ended up getting the AVA Humdinger, which was one of the relatively inexpensive ones.

http://avahifi.com/index.php?option=com_content&view=article&id=270&Itemid=239

Stuck it on, hum was gone. I was concerned about possible effect on sound quality...spent a few weeks burning it in, because I believe in that sort of thing - ran a couple of fans off of one of the outlets at night + while I was at work.

Anyway...against any expectations I had, it actually seems to have improved sound quality. More detail, lower noise floor, blacker blacks, better separation between tracks without loosing overall coherence. Nothing huge, but noticeable. Doesn't seem to be placebo; wasn't looking for that effect, in fact expected to possibly pay a small price in SQ to get rid of hum. May just be responding to fact that nothing got any worse.

This guy says that he (and/or someone he knows) experienced the same thing:

http://www.diyaudio.com/forums/power-supplies/246394-dc-blockers-mains-filters.html

This guys says he's not so sure (if you're talking about vintage arcade games):

https://pinside.com/pinball/forum/topic/how-can-i-improve-sound-quality

Long story short: dc blocker seems to have improved sound quality; the reason why is, I don't know the reason why. And I could be wrong. Would be interested to hear others' experience with dc blockers and SQ.

Speedskater

If the hum is intermittent, you might be able to find it's cause. It's better to fix the problem at it's source rather than use a patch. Do you have a little 'Kill-a-Watt' meter? As it might be line voltage related.

zingo

I agree to find the source of the issue, not mask it with more equipment.

bthogan

Thanks for replies! Re: cause, the problem with the sort of hum that I seem to have - "DC on the AC" - is that it can have off-site causes that aren't within my power to control. I went through possible "local" culprits - lights with dimmer switches, other appliances - and it didn't appear to correlate with any of those. It's not a ground-loop type thing, which I think can be fixed more easily within the confines of one's own dwelling.

I realize that this is also the sort of topic that can lead to theoretical debates about the very possibility of "dirty AC". All I can say is, my experience was that my toroidal transformer hummed intermittently, particularly in the evening (no hum/buzz came out of my speakers); it didn't correlate to my use of any dimmer-type power switch; the only appliance that might have caused it is my fridge, which it's not really convenient to turn off; and putting the AVA Humdinger between my amp's power cord and the outlet made the hum go away.

Speedskater

Some toroidal power transformer's are sensitive to high line voltage.

The DC won't make it very far on the power line. It's your house or a nearby neighbor's. But there are some exceptions.