I picked up David Kidds ERT 33 this past weekend and remembered why I fell in love with Fred's amps in the first place. I did miss some of the mids that I have with my 9/15 or with my AC30 so I thought about adding a G12H30 with my blue in my 2x12. I called Fred to order a switchhazel and mentioned that I had picked up the amp. He then said that he could change the 33 into 31 specs. The only difference would be that the midrange would be all the way up. This is the AC30 mid's setting that I like. The 31 gives you a mid control where you can back out the midrange if you desire. There will be no midrange control on the 33 conversion. I had a chance to play the amp and it sounds amazing. A killer vox styled amp with reverb and a /13 click channel for that amazing gain tone! Any of you guys with 33's might want to think about dropping the extra 2bills to have yours changed. I think that it is definately worth it!