I have a Tube Magic D1 as my amplifier/source. On my home computer, a constant hiss starts to be introduced at around 1 o'clock and gets louder as I turn the knob higher. This is a slight problem, as some of my quieter recordings of classical music require me to bring the knob to about 2 o'clock. However, when using the D1 with my Sansa Fuze, there is 0 audible hiss at any volume level. I'm currently using the D1 with my friend's Macbook and the hiss is also much less than my home computer, not becoming noticeable up until about 4 o'clock.
What can I do to remedy the hiss problem with my home computer? I'm thinking that it's the motherboard/USB inputs. I bought the computer pre-built and the motherboard isn't exactly high quality. I don't think it's the PSU, since I recently upgraded from the stock 220w PSU to a nicer Corsair 430w PSU.
If anybody has any ideas, it would be greatly appreciated. Thanks!