EMI w/ computer, peri-HD and DAC so close 2 amps

Its all powered from one ac outlet going to a power conditioner.

Its usually not EMI, its ground-loop common-mode noise. The thing to do if you are using USB is to power the computer and the USB interface (USB converter or DAC) from the same AC outlet. If you also have a CD transport connected, the power for this can also add noise. Power it from the same outlet as the DAC.

Another thing that works great is to use an isolation transformer like the Final Drive in the analog path from DAC to preamp or amps.

Steve N.
Empirical Audio

Use a network player like Sonos with wireless Wifi network connection to help isolate computers/music servers from audio gear. Also some power conditioning for the audio gear save power amp is also a good idea.

I would love some advice here as well...
I just got a mew iMac, had been using a macbook pro, and I am getting so much noise from the computer.

Did anyone help solve your issue?
how did you do it?
thanks
keil