Conclusion
The Mesa Boogie V-1 Bottle Rocket is a "secret weapon" audio processor for bass guitar. Used stock, it is an excellent overdrive and a very good preamp, if with a narrow sonic focus. But with the addition of the 500pf cap, it becomes a credible tube preamp for clean preamplification of bass guitar.
The result is not like Demeter, Universal Audio, Millennia Media, etc. It cannot compete with their capacity for slight coloration or high headroom. Instead, it is much more like the preamp in a vintage guitar tube amp. It is a bit wooly, quite sweet, noticeably compressed, and tough but relaxed-sounding.
I am using my V-1 Bottle Rocket as if it were the flavorful preamp for my bass amp (an Acoustic Image Focus 1 Series III that by itself sounds sweet enough and very clean, but is rather devoid of personality.) An Aguilar TLC compressor (set at maybe 3:1 or 4:1, with the threshold in the middle of its range) is just before it, and all other effects feed the compressor (I don't subscribe to the "clean amp for effects" approach; I like an amp with saturation and a real voice, into which I feed whatever I have, including spatial effects). In addition to its general duties, the compressor spares the V-1 needing more headroom: I still get plenty of amplitude dynamics into and out of the V-1, which is itself very responsive within its limited dynamic range.
Though by no means scooped-sounding, the modified V-1 Bottle Rocket does have very articulate, almost delicate highs, massive low end, and somewhat diminished upper midrange. Also, the treble pot can now be used for actual tone shaping: for real presence, it needs to be cranked; but rolling it off makes velvety tones that remind me more of the passive tone pot on a vintage bass than of the treble pot in a preamp of a bass or guitar tube amp.