I've never been able to get my Freqout to create sustained feedback, and my power supply offers 500mA. Maybe I'm doing something wrong. It begins to feedback, then dies off after about 2 seconds, usually in a weird glitchy way. I recorded a track on our first album with a Clark Beaufort (5E3) that had me holding double stops until they bloomed into feedback. I simply cranked the amp, hit it with a boost and found the right spot to stand. Worked beautifully.