Jon,
My LDR1B-V2 was the preamp we auditioned in your system. When comparing it with that ARC preamp, I heard the same kind of differences as when I compared it with my ARC-REF3. The ARC preamp's width collapsed compared with the Tortuga. Also, the Tortuga was cleaner and with better bass punch.
I'm going to be using the LDRxB-V2 as my main preamp/attenuator. I have to say that when I compared the LDR1B-V2 with the LDRxB-V2, I also found, as Morten indicated, that the 1B was slightly, very slightly, better than the xB. However, I anticipate I'll be very happy using the xB for the main attenuator, relegating the 1B to the role of level matching the bass amps to the M/T amps in my bi-amped system.
Best,
Robert
p.s. Morten, please don't forget that I need the yellow(orange? LEDs in my system and the Neotech wire, whatever you used in my LDR1B. Thanks