I recently bought the TC Electronics Spectracomp as I wanted a multiband compressor to play with. I had read hear that some people had problems with them being noisy and some didn't so I was pretty disappointed to find that when I plugged mine in it was quite noisy. The signal chain was: bass-->compressor-->audio interface-->headphones, so it could only be the unit producing the noise. The first thing I did was to go inside it and set the gain to 0 and the thresholds to max so the compressor was doing no processing at all, but when I hit the button the noise was there. It doesn't come with a power supply, so I had a look at the one I was using. It had come with a second hand pedal I had bought years ago and was unlabelled. I pulled it apart on a whim, and sure enough, it is a switch mode supply. I replaced it with one I know is linear, and the noise was gone. I've used this supply on a few different things over the years without a problem, but never on a digital effect. I'm guessing it't the AD - DA converters picking up switching noise from the supply. Whatever the case, problem solved and the compressor is fantastic. For anyone else who's had noise issues with the spectracomp, it might be worth checking your power supply before you send it back.