I could be sorely mistaken, but my understanding is that the v2 Terror does *not* use that particular tone stack; what you describe is the v1. As @aproud1 was saying, the newer Terrors have an EQ that actually cuts and boosts all bands.
I use a v1 Terror still, and yes, swapping tubes definitely made a difference. I wanted a bit more room to play with from the Gain knob's "edge-of-breakup" territory, so put a 5751 in v1; only about 70% of the gain as a 12AX7, so added more clean and clean-ish headroom. And it was nearly 10yrs ago, but I got me one of those head cases as well. Though I needed a different colour scheme to "match" the look... (orange and yellow. Yum.)
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The ad copy for the terror says it does. Directly from oranges website:
“The preamp section of the Terror Bass is the same valve design as used in the flagship Orange bass amp, the AD200. Just like its all-valve bigger brother, the Terror Bass is a classic, uncomplicated amplifier, designed to give you the best tone.”
and
“The Terror Bass is back and it sounds better than ever. With a valve preamp and a 500W Class D solid state power amp, the all-new Terror Bass sounds closer to our flagship AD200 than ever before.
Though the circuit is completely new, the Terror Bass retains the control layout from the original amp, with the addition of a Clean switch. This reduces gain and smoothes the top-end, giving this super-simple amp an even greater range of tones than its predecessor. ”
Sounds to me like it’s the same preamp with a couple tweaks, but I guess that depends on how you interpret the “completely new” circuit part in light of the other bits. I would hope that refers to their class D power amp design given the flaws of the original.
As usual for orange the manual is of no help in this case.

