If I may suggest to those with V12Rs,
Output Tubes:
Don’t be so quick to yank/replace/chuck those Ruby’s for others, some were the actual Shuguang EL34-BSTR tube version which sounded really good in that amp 1) if it’s biased right and 2) if you have really good vintage EL84s and 6922 or 12BZ7 tubes up front 3) have the right preamp/tubes in front of the V12R.
Bias/LEDs/Meter:
My local tech was a retired 40-year McIntosh tech, helped me to upgrade my V12R. He noted it’s not necessary to crank up bias to the recommended 285ma in the original owners manual (old / false / was never updated online). We called the prior designer at Cary together and noted having to drop it down to quite a bit or risk blowing the 4amp fuse periodically. Ended up with 5amp fuses, later. BUT, no longer an issue or need when we dropped it down under 220ma. Yes, as I recall, 35ma (per tube) and 210ma (per side/channel) was about right, sounded good too. Helps the output tubes to last longer too, don’t forget that part! No need to light those LEDs up, use a good meter, and those LEDs are not all that accurate or in sync with each other.
Input/Driver tubes:
The "R" version allowed for 12BZ7 (TV tubes), and IF you get a good vintage matched pair RCA or Sylvania, it does add interesting tone, rasp, and texture to the music - something Dennis Had came up with in the R. In a brief conversation via email, Dennis mentioned he still owns one, or diid a few years ago.
UL/Triode switch:
While the Triode/Ultralinear switch was cool in the V12R, i never felt UL was at the same level of sound as a regular non-switchable Pentode Push Pull sound like my Quicksilver 120 Monoblocks paired now paired with my Cary SLP-98 preamp.
Preamp Matters!
A really good preamp and the 6SN7s in my Cary SLP-98 along with the choice of interconnects used between the preamp-to-amp and source to preamp really helped dictate the final result for the V12R as well.
Once you put really good coupling caps and Hexfred Diodes in that amp, it jumps to a whole new level once again. Enjoy the V12R, it’s a fun piece. Sure liked mine. New owner loves it.