My Doubler arrived just in time to run off to an electric gig last night. First time out with my J Bass through the VT Bass and Doubler. Happiest I've ever been with my tone, though the fact that I just picked up a Bergantino HT210 to stack on top of my HT310 also played a roll.
I've been a bit concerned that this set-up has no parametric eq, but I didn't miss it. The VT Bass is tricky to figure out as the "character" knob has a difficult to pin-point (for me at least) effect on the eq. After many hours of sitting at home playing with the pedal, it's starting to make sense to me and I'm finding that I can really dial in whatever tone I'm looking for pretty easily and somehow don't miss a parametric eq.
The J Bass sounds fine through the Doubler without the VT, I can pretty much get the same sound I got through my old SWR stuff (which I don't hate). But, I like it a whole lot more with the VT, it really gets the sound I'm after. Whether the Doubler on its own cuts it for you will surely depend on what sort of sound you're after.
Thumbs up for Doubler + VT Bass!
Joe