I moved into a new house about a month ago. The power in the recording area (a former garage converted into a bedroom) is really dirty: I can't record guitar amps right now because the noise is so bad. But I also found out this morning doing some acoustic guitar work that the noise is getting in through my microphones when using a high-gain preamp. Here's a sample. The volume is soft, but I normalized into the transients so it shouldn't be too abrasive: AC Noise (if the hotlink doesn't work, open a new window and copy+paste) I'd first like help identifying this, whether it's EMI or radio interference. Secondly, I'd like strong opinions whether these less-than products will help: some solutions I'm looking at are the Monster PRO 2500 and Carvin AC120s. I'm only able to spend around $200 right now.