it was my mistake. i connected 8 and 16 ohm cab. i´d mail to bedrock if i could, but the company went out of business a few year ago. that´s why i´m searching like an idiot for a manual for my amp. i read one of another bedrockampseries, the 1600, and there´s the same, two jacks and minimum impedance 4 ohm, and in the manual they have written, that you can combine any cabs as long as the impedance does not drop below 4 ohms.
so we´ll see !! i´ll let you know if i blow my amp !! 😀

thanks, i solved the problem, the two jacks are wired parallel, so i can use 4 ohm, 2 x 8 ohm, or 2 x 16 ohm, cause the amp needs 4 ohm minimum impedance. the amp didn´t care about the rest, as long as the impedance dos not drop below 4 ohm.
btw, does anyone of you have the manual for the bedrock 1000 series ? can´t find one here in germany, or even in the web !

thanx boys, but ho do i connect two cabs ?
i have a jcm slash cab 4×12″, and it has a 4 ohm and a 16 ohm input for mono and you can switch them to 8 ohm stereo, so how can i connect this cab with for example the same type of cab ?