I bought an external DAC with balanced output exactly to avoid noise from the PC, but now I constantly get hiss or hum or whatever you call it from the speakers and it is affected by what the PC is doing. If the GPU is occupied the hiss gets worse. If the screen displays bright colors the hiss is less pronounced than when the display is dark. This is an external USB dac, how can the noise propagate through a digital interface from the PC? Or is it possible the noise is collected by the cable going to the speakers? Or through the mains? What can I do to get rid of it? Would connetcing the speakers to different electrical outlets help?