"CLX has a single 12AX7 driver stage, a different power transformer, a different output transformer and Dual Class Mode. It breaks up easier and has a bit more give - besides the EL34 voice.
UL does not have DualClass switch. Never did. Neither model has ever had Enhance Mode - the switchable tube/ss rectifier function.
The differences between the 2 models has varied over time, but has been stable over the last roughly 10 years. See:
http://www.fryette-users.com/forums/...-of-the-vht-ul
Difference between the D60 and D120 is the driver stage. The 120 has a 2-tube driver/PI stage similar to the UL. The 60 has the single stage like the CLX. Preamp voicing is the same, but because of the difference in output and driver stage, the 60 sounds more pissed off compared to the 120 which sounds more like a bulldozer coming down your street."