what makes power transformers buzzing

[samoloko]

Hi

I got a diy amplifier which transformer makes buzz
I have changed at least 5 brands Incl toroid type - Plitron (series 3000) , Avel Lindberg, Toroid Inc. , EI type , R-core but the buzz Is staying
I tried with DC filter and again - the hum Is staying

at the amp I feed bridge rectifier for power transistors, bridge rectifier for regulator board, Indicators, safety circuit - the secondaries of the transformer are not symetrical loaded
also I got 1 V diference between + and - rails

would you tell me what to chose In order to stop transformer buzzing and to clear the differences between + and - rails

[Elvee]

If you use full wave rectification, differences between the + and - rails (and current consumptions) are irrelevant.
On the other hand, a damaged or asymetrical bridge rectifier can cause a polarity imbalance in the transformer, causing noise and vibration.
You can try to disconnect in turn each winding of the transformer until the buzz stops.
There could be other causes though: try to identify the fundamental frequency of the buzz. 50/60Hz or 100/120Hz have different causes.

[AndrewT]

is it a mechanical buzz from the transformer?
or
an electrical signal buzz from the speaker?

[samoloko]

the noise Is mechanical from transformer

[Eva]

Your description suggests some mistake in the rectifier circuits. Could you post a schematic?