I recently purchased a used Aguilar AG 500 amp and a Bergantino AE410 cab. My problem is, when I play my bass at moderately high volumes (master knob at about 10 o'clock) my clipping light goes off and it distorts a bit. This also happens when my master is at the lowest possible setting. Turning the gain down helps the problem slightly, but not a whole lot. When I first noticed the problem, I was plugging the Aguilar in to 2 sort of low-grade, mismatched cabs (a Carvin BR210, and an Acoustic B410, rated at 4 ohms and 8 ohms respectively, and I tried running them both parallel and in series). I thought that the difference in impedance was making something go all wonky and causing the clipping, but it is continuing to clip with my Bergantino, which is rated 800W at 4 ohms (my amp puts out 500W at 4 ohms). So I am stumped. Am I clipping the pre? Could there be a loose connection somewhere? I don't know much about this sort of thing, so any help at all would be appreciated.