Hi Morten,
If there's a balanced version of the tube buffer in the works, I definitely want to try it. As you know, my biamplified system using an LDRxB-V2 (with absolute phase switching) and an LDR1B-V2 to trim the level match the bass amp is a prime candidate for a buffer.
I have to say, though, that converting both of my Tortugas to battery power took my system to another higher level altogether and I'm curious how the active power supply of a Tortuga tube buffer would affect that change.
Best,
Robert