noisy transformers

Here is one, quite a few amps I have owned have had humming tx's, mechanical, so whether it is simple cheap design with not enough iron.

But is it the mains, you can have dc on the mains which will saturate a core and make it buzz.

so the question is, are there any devices/tweaks out there to keep your mains happy in this way?

cheers....

 

In a word - no. The only permanent solutions include the replacement of the offending transformers by something substantially better or by introducing a mains isolating transformer (no bad thing if large enough - 5KVA Plus) into the equation.

 

just make sure its well regulated.if you use a large transformer with a small load the output voltage can increase to outside the manufacters recomended limits

 

I'm curious; if the explanation isn't too complicated, how is it at DC generates a buzz?

As it's a mechanical buzzing, is it something that could be reduced by some sort of damping on the transformer? My pre-amp has a bit of a noisy transformer and I've wondered about this...

 

The lower the frequency, and higher the load, the bigger your transformer core has to be, if its too small, it will become saturated and buzz. dc is zero hz.

 

Indeed, which is why I was naively surprised this would cause a buzz; I kind of thought it would have to be some sort of AC signal to cause this. Not doubting you here at all, just seemed counter intuitive to me.

 

OK, just a couple of seed thoughts for consideration:
Transformers over a certain VA rating have less of a voltage change between light and full loads. The 5KVA unit in use here has a specified regulation of 4% which means the secondary output will vary by just such an amount from no load to full load.

There are quite a few causes of mechanical buzzing - the most common being that the core is saturated by the DC content of the mains supply before the AC is able to do any useful work. Another common factor is loose laminations which 'flap about' under load and cause the characteristic noise. This last problem causes odd order harmonics to be introduced onto the DC line and means that the rgulators have so much more work to do so simply damping or isolating the transformer will only cure the mechanical noise, not the electrical product. Hope that helps a little.