Just picked up an AG500 on Kijiji (Canadian Craigslist) and I'm concerned that someone might have knowingly sold me a faulty unit. It's partially my fault, I didn't meet him at his house, instead opting to meet him in a public place to do the deed; everything seemed legit. He said it was just collecting dust but everything was working OK last he checked, he was selling it because he'd not used it in a few years. So I paid him the cash, it was a good deal, and when I took it home other than a bit of dust in the pots that cleared up as soon as I gave 'em a few twists, everything was honky dory and I had a nice practice session. Well, I fired it up today after putting it in a rather expensive rack case and it started making the strangest buzzing and humming sounds. It did work OK (I see what people mean about the thin low end but it's pretty nice). The buzzing sounds are really bugging me and I hope this guy isn't trying to pull a fast one on me. I took a video of it, the guy is still not answering me but he dropped a few cookie crumbs that led to his home address, so, before I rectify the problem I'd like to know if there's a quick fix that can solve the issue the easy way. I've posted a video of the issues - the cab is mic'd with a sennheiser e835 through a cheap ART USB mixer, so you should get some idea of the problem. .