MINE is very much a tube preamp sound. Tube regulated PS, 12at/12au7 setup. TONS of gain. I have NO problem running the reduced output of the Bolder SB. It's definitely on the warm and lush side but that's what my setup needed. I've had several other pieces in my system costing several times more and for me, in my system, this is a winner until I want to spend a LOT more. So you know where I'm coming from, the rest of the system:
Bolder Statement Mod SB3
Bolder Ultimate PS
Odyssey Stratos Mono Extreme SEs
Dynaudio Contour 3.3's
Harmonic Tech Pro-9
VH Audio Pulsars
Substituting the KTA-100 amp for the Odysseys is actually MORE bass and IMO smoother (I'm a sucker for Class A amps) but obviously not as much power - though it's not as big a drop as you'd think.
Scott F. has the same preamp with the same mods but has VH Teflons in the tube couplers. A bit more detail and a bit more forward but still nice.
In any incarnation, this preamp is very very accepting of tube rolling. Stock EH, vs 60's RCA Blackplates (this is what I run with a Tele in the power supply), vs NOS Mullards - 3 completely different sounds.
Remember this is the entry level piece. The next step up is a 2 chassis (PS and preamp separated), dual mono, etc. The basic is a sub $2k piece that can be made to sound pretty much however you want. It's a simple circuit like the amp.
The entry level is more 'tubey'. The 2 chassis is more neutral and 'accurate'. Both are receptive to tube changes and other circuit tweaks.
Bryan