Ho Hum

Bah.

I have noticed a slight but annoying residual hum coming from my speakers when my system is idling. I can hear it late a night from about 8 feet away and it's just audiable but still annoys, I imagine that it's also probably not helping the sound quality.

I have a mains spur with 4 unswitched sockets and have discovered that the hum disappears when everything but the amp is plugged in.

I assume I have some kind of earth thing going on so simply put how can I fix it for as little money as possible?

I have unplugged the CD and Tuner which cuts it right down but I really can't be arsed to keep plugging and unplugging stuff.

So any thoughts, I wonder if a 6 way block of some sort would cure it by sorting out the earth to single point maybe...

As you can imagine I have no idea what I'm on about, so help would be much appreciated.

 

have you tried re-arrangeing the order that stuff is plugged into the spurs?

Do you know if it is a spur or a ring?

 

I had this problem once, and it turned out because I'd very stupidly got my overly long pre-power IC loosly coiled under my power amp . Doh! I hasten to add I hadn't consciously meant to put the cable there, but I must have sort of stuffed it out of the way at some point without thinking about it...

 

does it still hum if you disconect all the inputs to the amp with everything turned on?
could be the transformer on something is inducing a small voltage into one of the i/cs,or even the input stage of the amp

 

Yepp! Sounds like you need to experiment with the routing of your cables. Try to ensure that signal cables and mains cables cross at right angles if possible. Another possibility is that some of your boxes are too close to each other, or perhaps too close to a TV or video. Applies to cables as well as boxes. Experiment!

 

I just solved exactly the same problem in my system. It only started happening after I had taken out the Isolda speaker cable and put back the OCOS cable....I was starting to get worried that I might have to backtrack on "there was no difference" ...

However, in swapping speaker cables around I'd arsed around behind the rack a bit and a few other cables had got moved about. Turned out the pre to power ICs were the culprit. Re-routed them so they were nowhere near any power cables - problem solved.

When I finish my DIY power amp I'll be able to have balanced connections between pre and power - presumably balanced cables are immune to that kind of mains interference?

Michael.

 

Micheal, i dont know much about balanced. But i wouldnt think they would be imune just by virtue of being balanced.

/awaits being shot down and told how wrong i am

 

pass the shotgun
in most cases balanced will avoid hum,something to do with the "noise" being the same on both cables,at the input one conductor is inverted,so the noise on one line will out of phase with the other so's they cancel.

 

My old aura preamp both hummed and had quite bad crosstalk. The Accuphase preamp I now use is silent. A case of better design and manufacturing IMO.
Try taking any phono amps / transformers out of the loop and seeing if you still get any noise. That's were I'd start.

 

Discovered that it's the CD player that is causing the problem, have plugged it in elsewhere and lo and behold, silence.

Thanks for the suggestions all.