Currently Being ModeratedDec 30, 2010 2:10 AM (in response to trammapoline)Re: Noise in Record Out - Spider IV 15
Ah, I just found the answer here: http://line6.com/community/message/151247#151247
The problem is indeed a ground loop. I was running the FastTrack via USB from a computer with the same earthing as the amp; when I run the laptop on battery, no problem. Massively relieved! (I also tried a mic/guitar pre-amp as the intermediary, but I guess its impedence wasn't ideal, and maybe its lack of earthing was also an issue) There is still a slight bit of noise, but it's only the low-level stuff I'd expect from most amps.
Just one short suggestion, though: if your search didn't default to searching documents only, it would be rather quicker to find stuff