"Technical Pro powered speakers have Mic input. OP doesn't need to modify the amp at all. D'OH "

There was ot enough gain. I connected line level to it and there was plenty of gain. The problem was the same on ¼" and XLR which feed separate OP AMPs.

BOTH INPUTS SAY "LINE".

So, are you really sure of that ? with a higher input to either the amp clips just fine, no distortion. If there was a fault in the amp it would have to be rtow separate identical faults causing the same reduction in gain in two separate OP AMPs.

Is this what you're telling me ?