What a lovely sound!
It takes all the things I love about the better 12BH7s and "kicks it up a notch." Thing I noticed first was even better dynamics and what seems like an even lower noise floor. The better 12BH7 I've heard hardly leave me wanting when it comes to resolution.. but incredibly, the VT-231 seems to top that. Tonal reproduction is terrific, as well. It's a wonderfully smooth, airy, neutral tube. Bass is lean, mean, and fast.... but has excellent punch and impact when the music calls for it. The mids are very transparent, detailed, and spacious. Smooth, detailed, and possessing terrific depth, the mids are nothing short of jaw droppingly good. Treble, too is, perfect for my tastes. Not recessed, not excessively bright.. but balanced, extended, crisp, and smooth. There's a romantic quality to this tube's sound that makes me want to keep listening with the HD800.
To date, this is my favorite to in the Crack. Simply wonderful... and what sounds like a match-made-in-heaven with the HD800.