as the title says, im talking about the RP 500... When i plug it in my computer (by using the usb cable...) all works, but i don't hear a sound !! My computer tells me that im plugged and X-Edit works well, but i just dont hear what i play, it's like playing unplugged... any advices or something that could help ??
There is no output thru the USB cable on the RP ... you have to run a cable from the output jack on the back of the RP to your mic in or line in. The line in will work better than the mic in though, and be sure the RP switch is set to "mixer" on the back when you do this. As for the cable just use a standard guitar cable and buy one of those little 1/4" to 1/8" adaptors at Radio Shack or Walmart or some place similar. Unless you have some nice monitors or are running through a home stereo amp or something you'll have to keep the volume low ... the frequency response will rattle and vibrate cheap PC speakers quite a bit although they will work.

If you have a cheap amp or a practice amp or something laying around that will work a lot better than PC speakers and you could just leave it next to the PC.