The VH4 is an all-tube amp with four individual preamps, integrated midi-switcher and much more.The clean channel is one of the best in the industry, with plenty power and lots of percussive, piano like punch.The crunch channel is very pleasing for bluesy play or with less gain to resemble a vintage clean tone. Crank the gain up and it becomes a nice broad and open crunch a'la AC/DC.The third channel (heavy) is simply unbelievable. It has big dynamic ranges, from playful little licks, tasty solo work, to all out metal gain. The tone will not lose definition, though. Even at high gain selections, with humbucker guitars, it speaks straight from the artist's fingers. This channel is easy to play for the intuitive. It cleans up with guitar volume rolled off, and then comes on like a freight train when needed.Channel four starts where three leaves off. If gain is your thing, then channel four is sure to please you. It compresses more than three, retains definition to a large degree, and just shreds with big bass and strong high end. It is smooth distortion, creamy but authoritive. Loud.In the power stage of the Diezel VH4, each tube has a tube fault indicator, and a separate fuse. In case of tube failure, the fuse blows and takes the duet out of the circuit. You will finish your set with two tubes, instead of a dead amp.The power amp has a master volume, presence and deep controls. There are parallel and serial returns to the power amp. Two sends give you flexibility far beyond any standards. One of the sends is front panel/midi switchable. The parallel return has a mix control on the front panel in the master section. Oh, not to forget the channel inserts for channel one through four. These can be manually or midi controlled. The Diezel Midi system has 16 channels, with 128 program changes.