MAJOR hissing with Alien DAC

[jinp6301]

Hey folks, I received my Alien DAC a couple of days ago and there seems to be major hissing when connected with my toshiba laptop running XP with the power cord connected. It starts hissing even when theres nothing playing. I tried Kernal Streaming, ASIO and nothing and it still seems that theres a lot of hissing when I raise the volume to a decent level with my Supermacro LE. and before you ask, yes its not the amp. The amp doesnt hiss when its connected to any of my mp3 players. Forgot to say that I'm running foobar.

The weird thing is that it works fine when connected to a Power Mac G5. I have yet to try it with any other computer.

I think its the power supply by the USB thats causing the hiss but I dunno.
Any help would be appreciated.

 

[error401]

Yup, sounds like the switching power brick is injecting a lot of noise into the supply lines. If you have a good quality DMM you should be able to measure this with the ACmV range. If this is in the audio frequency though the regulator and caps should be able to filter it out. Are you using a regulated or unregulated configuration? Perhaps the USB supply isn't putting out enough voltage to keep it in regulation (measure the DCV on the USB power lines and compare to the configured voltage of IC3). The dropout voltage for REG101 is only 60mV, but if it's configured aggressively you might not quite be high enough.

If you find that it's definitely in regulation then your only real recourse is external power for the DAC, or using battery power on the laptop.