This may be kinda out topic

I built a high output EI250 transformer, 70primaryw/7secw it gives from 120V60hz to 13V/80A output DC from a bridged diodes. This is my first school project and I want to power up a car sub amplifier with it, I have a 1.5F cap. My problem is when I plug the amp there's no noise at all, but when I plug in the audio source in the RCA, there's some severe noise, likely to be 60hz, also it does when I touch the rca plug with finger. I added a 100000uf cap for diode output, it still does the noise from speakers.
I never get noise when I use a 12V battery or in car though, how can I fix the problem? Thanks!

I tried to move the amp 2-4 meter away to evade the flux leakage, no chance,,,

 

The power supply output needs to have the - (negative) attached to ground, the same ground as the stereo the RCA's are coming from.
The noise you hear is the floating output of your supply being grounded through the RCA's (and thats not a good thing).

 

What should I do now? Do I need a wire from (-) to the wall socket ground?

 

yup, that'll help

 

Ill try that, I fryed the bridge diode yesterday llol need one set more powerful. But the source signal is from a logitech 5.1set and the plug to wallsocket is only 2 way, ungrounded, that will still makes noises?

 

waaaiitt a minute... sounds like you made a +/- 6.5V setup which is definatly going to cause problems with most car amps!!! You should have 13v at one polarity off the secondary and a center tap going to amp ground !!

check out ePanorama.net for information on building power supplies.....

 

I mesured output with multimeter is 13.2V DC

 

If you didn't use this type of design you might need to go back to the drawing board:

Edit: oopps wrong link...

Full-wave DC power supply

 

now he'll really be confused.....

 

I used a brige diode with 100000uf filter cap