After reading this thread I remembered that a friend of mine used a BK for a few years, so I asked him about coloration, and he told me exactly the same. Coloration was never a big problem as long as you keep the levels fairly low, not super transparent, but no problem working with. But if you feed it to hot, things get worse very quick. Looks like it has a very limited headroom.

I wonder that there are no mods for this unit. I guess it didn´t sell to bad, there should be a lot of units out there.