So the other day I had put in - as I mentioned earlier - Sovtek LPS tubes in V1, V2, V4 and V6 of my Twin Jet, with Chinese in V3 and V5. I've played a little since then, mostly with other people, until this morning. I spent a few hours playing, and after only a short time in, found I was very disappointed with the amp. Recently, I've been playing my 101b a lot because I did a full retube, and it sounds gorgeous, so today when I switched over to the Twin Jet, I was shocked at how loose and undefined it was. I remembered that when I recorded the clips to showcase EL34s in the Twin Jet, I had all Chinese except for V6, so I decided to undo what I had thought I liked so much. The result? Magic.
There's something about the Chinese tubes in V1 - V3 that against all odds, make it much tighter than with other tubes that are known to be less fizzier and more defined. I don't know how the hell it works and I won't try to understand, but I'm starting to think the Twin Jet sounds best with Chinese tubes in these spots. Not only is it tighter and more defined, it just sounds better ; more raw, more aggressive, and very little flub. I've tried Sovtek, JJ, Tung-Sol, NOS, and probably a few others, and I keep coming back to the Chinese. Sure, the PI sounds better with a Sovtek LPS to me, but for all the other spots, I'll be sticking with the stock Chinese.
The issue of fizz.
First off, I feel like the KT88s are inherently more fizzy than the EL34s I have, but not enough to escape the power of the Twin Jet's knobs. What I've noticed is that a lot of people seem to lower their mids and turn up master presence, keeping the treble control in a somewhat "neutral" range. I'm hearing quite a bit of overlap between the master presence and the mids control, so what I would suggest to anyone finding the amp too fizzy is that you raise mids and lower master presence until the high end fizz is in check. For me, mids are slightly below noon - maybe 11:30 - and master presence goes anywhere from 11 - 12:00, depending on volume. If it's still fizzy, lower treble! I keep mine at about 10:00, but I think anything under noon should do well to keep fizz in check concerning that knob. With this in mind, I'm finding no problem using the Chinese tubes with gain and channel presence turned way up, while keeping fizz in check. Probably worth mentioning: I go back and forth between a Bogner 4x12 with G12Ms and a Mesa Recto 4x12 with G12T-75s.
For inquiring minds, the reason I didn't go with thetubestore and their TRUE TAD preamps was a) AES seemed way cheaper and b) thetubestore.com is currently sold out 
