I just got my modded stack back from TDSS.
Before I start, let me say I've used several dozen good SS or Class D amps, not tubes, so these reflections are on that basis.
My audio friends have several very good tube amps, but comparisons with them would not be valid.
From the first notes I knew the mods were a great success.
I loved my stock 10H,ST10 units for all they did so very well, but felt they could use a tad more air and openness on top compared to my favorite amps. Well, that one caveat, not a showstopper before, is now gone, gone, gone. From Bach fugues to Alison Krause to Ahmad Jamal and Dimeola/Dilucia/Mclaughlin Live to Andy Summers' power fusion, the modded units put me in the venue in as convincing fashion as I have ever experienced from 2 channel. The overall sonic signature and balanced tonality is much the same as stock units, but the soundstage, noise floor, very low level detail and airiness is greatly enhanced. Separation, width, depth and most notably the sense of performance space is the best I've ever had in any system of mine. Images often float in the air far away from the speakers on well recorded material. It is very cool to experience this 3D presentation.
This is the best amplification I've owned, and up there with the best non-tube gear I've heard anywhere. A friend has a big $ Spectral stack, and this reminds me of that for its speed, transparency and low coloration.
Note that these are very, very clean and focused; they add nothing I can tell, neither warmth nor brightness nor any euphonic editing. As in all matters, this may or may not match your tastes and system.
Kudos to Nuprime and Bob Smith.
Bob tells me they take a while to fully break in, and I can hardly wait. They are worth every penny and then some as is, if SOTA transparency is the goal.
If you already like the sound of your Nuprime and you've been thinking about the TDSS mods, for my money this is the real deal. It really shows off what these awesome pieces can do at their best.
If you don't own Nuprime, I think you'd have to pay far North of $10k for a HP amp, DAC, remote preamp and power amp to match these, and much more to better them. On top of that, they are very small, energy efficient, well built and look cool. Am I in love? You bet!