The quoted response from Db-r seems logical. Obviously if someone was mis using any equiptment and it fails repeatedly, he can't keep fixing it for free.
However...in my situation, my amp had a intermitent (sp?) turn-on or power-up problem. It had this problem before I had access to a dd-1, after it was dd-1'd, and before I sent it to db-r. $150 later, I was told there was something loose on the board and he soldered some wires underneath it. He also changed some caps that are known to fail but they hadn't yet. .Before I got the amp back from him is when I was told not to use the dd-1 on it or it would void his warranty.
The amp came back doing the same thing it did when I sent it in. Granted, the problem is intermitent, and the amp will turn on fine and operate fine, sometimes. So I understand the possibility of it not acting up when he had it. When I offered to send it back, and even pay the bench fee again, he said I'd be better off to just sell it. I've put it in other vehicles, its been hooked up to a battery on my kitchen table, and it does it regardless of the "install".
The "buzzing" sound some class d amps make internally when they see clipping (thanks Tony), is the same sound mine makes at turn-on. At the same time sending 110-120 v to the outputs. Even with the rca's unhooked. Power, ground, remote only.
Sorry for the novel, but my issue has nothing to do with gains, clipping, voltage, volume, impedence, the grass being green or the sky being blue, or a dd-1. I know it, he knows it. "pass the buck" comes to mind and I feel taken...