What exactly is the difference? The "C" is just brighter than the"A"? Josh posted the "C" has a bigger bottom and more low mid growl. I checked mine and it is an "A". I would prefer more bottom and low mid growl. I don't know about brighter. I also notice, and have been told by others, the Wizard MC ghost notes a little with the volume around four. I would imagine this has nothing to do with the Tranny and more with the power filtering. Not that it is a bad thing. There's a fine line between under and over filtering. If I had to chose under or over, I would take a little under for the "feel". I'm sure this is part of what makes the amp sound so good. I am very happy with my amp, but I am always looking for upgrades in tone.