Several days ago I received a new Yggdrasil DAC that I'm auditioning. My old DAC, a modified Music Hall 25.3, has been great but I've been itching to try out some of the newer ladder DACs. I currently run my DAC into a Tortuga LDR3.V25 following by TPB.V1 Tube Preamp Buffer running with 6H30 tubes.
After a few days with the Yggy I was about to conclude that while it's a very fine DAC indeed I was missing the smoother analog sound of my old DAC which has a $250 NOS Mazda 7308 tube in its output stage. Then I switched out the 6h30 tubes in the buffer for a pair of Genalex Gold Lion ECC88/6922's and the sound of the Yggy with the buffer running 6922's was instantly transformed into a silky smooth analog machine reminiscent of a vinyl rig. All of Yggy's information was still there but with the 6922's it was all meshing together rather than every instrument sounding like it was recorded in its own soundbooth. (maybe they were!!). The sound stage became deeper as well.
Something to keep in mind as you try out various DACs and such. The more I listen to our tube buffer and the more things I try with it the more it's becoming an essential "makes everything sound better" machine that happens to be called a tube buffer. Apparently it also has multiple personalities depending on the tube type you run in it.
More info on the TPB.V1 Tube Preamp Buffer here => https://www.tortugaaudio.com/products/preamp-buffers/tpb-v1-tube-preamp-buffer/