Power Transformer Noise?

Not sure what the problem is but several pieces of my gear are making quite a lot of hum. Not in the audio signal, noise in the room from the boxes themselves. I am assuming it is the power transformers humming. :?: I know I have gotten this noise out of second hand transformers I have used while expirimenting.

What causes this and is there any solution?

Bump

Sometimes loose laminations will vibrate. Try gently tightening the bolts that hold the transformer together (with the unit unplugged, of course).

If the transformers are toroids, the noise is caused by DC. Use a mains filter to remove it.

Best regards,

Mikkel C. Simonsen

I have had transfomers hum when I used polypro caps in the powersupply of a guitar amp. The amp has Si diodes the surge current and the Si diodes not being matched caused the toroid PS distress. Toroids don't like any DC like posted above.

The fix was a 1 ohm resistor between the diodes and the first filter cap. I had a 1 ohm power R that why I used 1 ohm maybe one could go lower?

Thanks!
I?ll try tightening them tonight.

Is a power conditioner a mains filter or is that something else entirely?

A filter for DC is often a 4700µF cap with two 3A diodes accross in opposite directions.

Best regards,

Mikkel C. Simonsen

[quote author="Viitalahde"]That means a separate filter at the AC input. AC inlets come with filters and you can add a separate filtering block inside the unit, too..[/quote]
The AC inlet filters don't include DC filters though - there's not enough space. I have never seen a standard "factory-made" filter with DC filtering infact. They are mostly made for EMC compliance.

Best regards,

Mikkel C. Simonsen