www.kolumbus.fi/juho.lepisto/Feedback.mp3
Distorted feedback.
Edit: Played around with distortions and mic and remembered that you were looking for this kind of sound.
Still needing it?
That's one minute clip full of feedback.
Edit 2: Very nice when listened with headphones. Felt like there's a feedback loop in my brains. I listened to it woth low volume and still I got a headache. Sick!