Transformer hum

[Bent my VU]

Has anyone got any tips on reducing transformer hum from equipment?

I've done a fair amount of sound prooofing in my writing room and the hum from a few bits of gear is really starting to get on my nerves.

Could it be a dirty power issue? or is it just the nature of cheap transformers?

[jithknot]

This is from the PS Audio website

"Hum inside equipment is generally caused by DC voltage on the AC powerline. This voltage will make transformers in equipment buzz and hum."

and this might help,

http://www.psaudio.com/ps/products/detail/humbuster-iii

hope this helps.

[no-fi]

hmmmmmmm......
(haha, I should be a comedian!!!!)

I have a couple of bits of gear that make (accoustic) hum too.. though they have done it at multiple locations and it's only those pieces that do it, so I wouldn't expect its a DC bias on the mains thing, unless everywhere I try them has that problem. and all my other gear is somehow DC proof.

I always thought it was loose windings or transformer laminations - something to do with old glue losing its hold... if there was a simple/cheap trick to get transformers not to hum anymore I'd be all over it. hell, if someone offered it as a cheap and fast service, I'd have a couple of pieces of gear apart today and the power transformers off to them tomorrow....

[Thirteen]

hmmmmmmm......
(haha, I should be a comedian!!!!)

I have a couple of bits of gear that make (accoustic) hum too.. though they have done it at multiple locations and it's only those pieces that do it, so I wouldn't expect its a DC bias on the mains thing, unless everywhere I try them has that problem. and all my other gear is somehow DC proof.

I always thought it was loose windings or transformer laminations - something to do with old glue losing its hold... if there was a simple/cheap trick to get transformers not to hum anymore I'd be all over it. hell, if someone offered it as a cheap and fast service, I'd have a couple of pieces of gear apart today and the power transformers off to them tomorrow....

Some tranny's laminations are clamped by 4 bolts, they can be tightened. Some have a metal enclosure around them that is wrapped around the edge of the laminations, and these edges can be bent tighter. Some are due to loose mounting screws to the chassis.

[Futureman]

My biggest 'hummers' are my Prophet 5, LinnDrum. I'd be interested to know if other Prophet 5's and LinnDrums are the same. (Accoustic hum)

Regards
Mike

[Kurt]

Pretty much everything in my house hums. I was told by the electricity people that it's caused by the windings getting loose, caused by fluctuations in the voltage. When I pointed out thet they supplied the voltage and it might be good if they fixed the fluctuations (not to mention my stuff) I was told that the "acceptable" fluctuation was +- 5%. So for a nominal 240 supply it could go from 228 - 254 and still be within spec.

[Milo]

The state of power in Australia is not good (dirty), and getting worse, according to electricians: new standards are just beaurocratic twaddle, and power station maintenance has declined.
Not verified: one sparky told me that, according to the federal government, Australia now runs on 230 volts, not 240, to conform with Europe. However, they add that the switchover is up to each state's discretion, and no actual change in the power supply setup / infrastructure is compulsory, ie nothing has changed.
I you have oodles of spare cash, I read an article a few years back on a studio owner in NY who was obsessed with AC hum. He got a tech to remove the power supplies from every single piece of kit in his control room, put all the supplies in a separate shielded room, and run DC only to everything. Simple.

[Kurt]

Or run everything off a UPS.

Deja vu.. I think this conversation was had on the old forum.

[Bent my VU]

If I could just get my A90 to stop humming that would do for now... I've tried teaching it the words but it hasn't helped.

[Kurt]

My guess is that once they develop a hum, they'll always do it. You could try potting the transformer? Soak it in a highly flammable mix of parafin and beeswax. I actually want to try it on a guitar pickup but we have a gas stove, apparently it's not a good idea!

If I could just get my A90 to stop humming that would do for now... I've tried teaching it the words but it hasn't helped.

[Bent my VU]

My guess is that once they develop a hum, they'll always do it. You could try potting the transformer? Soak it in a highly flammable mix of parafin and beeswax. I actually want to try it on a guitar pickup but we have a gas stove, apparently it's not a good idea!

If I could just get my A90 to stop humming that would do for now... I've tried teaching it the words but it hasn't helped.

Yeah I've had a few sets of pickups wax potted - I never thought of doing the PT. I'll open the A-90 up tonight and see what the tranny looks like. If it looks easy to remove I might even be able to replace it for a better one quite cheaply.

I'm also looking into hiring a power conditioner to see if that changes anything.