ARC VT 100: MkII vs. MkIII?

Perhaps you mean the MK-I vs the MK-II. The ARC web site makes no mention of a MK-III. I did have my unit updated to MK-II in the spring. The update includes fitting a removable IEC power cord, addition of a fan, and adding two small circuit cards containing additional power supply capacitance. The update yielded better dynamics and more of a sense of "sonic ease". At some time, I would like to explore updating the power cord.

Sparky57: You are basically screwed. The MKIII is out. It is an $1,850 upgrade (I think).

Cool! I'm always looking for better. I bought the unit used for $2800 and spent $600 on the upgrade. I couldn't care less that I don't have the latest. I will be curious as to the changes / sonic improvements. What I would really like is the ability to bridge the channels to offer the ultimate upgrade - another!

The newer model has a longer tube life besides better (possible?) sonics. I probably will go for it!

The Mk3 adds a switch for bal/single ended, 12V power on/off trigger. Internally, it now has JFET for input, followed by a 6H30 driver/gain, and a 6H30 follower driving the 6550Cs. There are now four internal bias instead of two. The upgrade will set us back 1895 from Mk2 and 2695 from Mk1. I do not know how different the sound would be from the Mk2. BAT has been using this tube in their preamps for over a year now. Why ARCs moving away from 6922 for their new design? Could REF 3 preamp replace REF 2 next year to correct the tubey sound of REF 2? Oh! well.....