Likely the TB500 #12 > Twin's > Mc2300 > K120's. The final solo has false-harmonics that were truly cosmic in that era...maybe because of the aluminum in the Beans. Yet to own one (yet) to confirm.
Truly a beautiful version of CAT....maybe the best ever.
Now I cheated & checked Waldo's site. http://www.wald-electronics.com/preampmods.html
I love this era.