Check out the Neunaber Neuron. It reminded me very much of a Mark IV. Right down to how difficult it can be to dial in an exact tone. (Due to the fact that every knib is extremely powerful & it's quite easy to get lost when tweaking). It has amazing cleans, a very Boogie like crunch & can chug...
Do you have the output knob turned down? It's the bottom right knob on the front. The knob on back next to the loop is send level. The output knob on front is return level. Noon on both is unity gain. I thought the loop on mine was broken when I first got it cause Output was turned down.