Buzz Noise on outputs with inputs attached

[akunec]

I have a noise problem on my parelleled 4780 amp. I have a lot of noise coming out the outputs. I hooked up the outputs to my scope and it looks like a half sine wave ~ 60hz, then 0 v then another half sine wave in the other direction. There is a gap of about 2 periods between these half sine waves. Does anyone know what is causing this?

 

[peranders]

Have you checked youir supply voltage? Is it "DC" or something else".

What happens if you shorten your input? Have the two channels the same behavior?

 

[akunec]

Yah, both channels have the same behaviour (both use the same tranny and rectifier), the noise doesn't change when I short the inputs?

 

[akunec]

Thanks for the help. I checked out the 2 supply voltages on the scope and they seem pretty bad. (looks like lines going up and down like ^^^^^^. )

I'm currently using a 400VA toroidal transformer with dual secondary 21V outs. The 2 coils are attached together to form the ground, while the other 2 wires are rectified using 4 MUR860 diodes.

Would it be better to leave the 2 coils seperated and rectify them individually using 8 diodes?

I have 17600uF total between 2 parelleled LM4780s. Is this enough?