I've been experimenting a lot lately on patches that could turn my guitar into something that's a little bit more than a plain electric guitar. ALthough i have been quite successful on the soft side of this endeavour, i am faced with a few problems regarding the connection between my laptop and my amplifier. One is the latency, but i m not too worried about this since i m running PD on an old HP with Ubuntu Studio 9.04 (it can only get better when i switch to a newer machine, right?). Another problem was that of the "manning" of the machine, which i managed to solve by hacking a usb game controller, just like anybody would.
Now here's the real issue. My gear setup is roughly as follows :
guitar --> usb soundcard --> PC (PD) --> usb soundcard --> Amp
The sound card is an EMU 0404 (usb), and all in all ive been pretty satisfied with it's sound. The problem is that for some reason i can hear some noise coming from the amp, not like a constant hum like a ground loop would create, more like the "voice" of the computer. The noise actually changes with something that is correlated to the CPU load of the laptop. Yet there is definitely a ground loop - like noise as well, which can be greatly reduced by unplugging the pc and letting it run on the battery.
So here's my question : has anyone ever encountered such a problem? Do you know of an electronic device that could reduce this noise?