Really guys- the current PT100 doesn't have anything to do with a 5150III- other than I was using one before, and really liked the ch2 on that amp. John knew what I dug, and built a completely different amp, using his standard OD100 clean (the best in the biz IMHO) and then ch2 and ch3 are his own creation, based off knowing what I like.
The dirt in the PT is pretty much modded Marshall in character. John has described it to me as being like a modded out JCM800. It does hi gain of course but you can get great lower gain Marshallesque tones with it too (I use the gain on ch2 on 5, and I use it with Don Henley like that, for example I play a LP on Hotel Cali with gain on 5 and bright switch off and I think it sounds appropriate for the song).