Hmmmm ...
Well, let me preface this by saying that this is just an improvised thing. I like my Underwood for its dependability and volume without feedback for my uses, but I would never argue that it's the best sounding pickup out there. But it's what I have, and it's served me well.
I also play guitar, and have a Boss AC-2 Acoustic Simulator pedal, which basically makes an electric guitar sound more like an acoustic guitar. I decided to try it with my Underwood. Well ... I like it. I just spent an hour messing with the various settings, combining it with various eq settings on my amp. I elevated my amp on a stool pointing at me, and got way more behind my bass than normal, so that the majority of what I would hear was the amplified tone. I plugged into my FDeck Pre/hpf, then into the AC2 and into my amp (Line6 Studio 110 as discussed
here).
WIthout the pedal, I have found that I need to cut treble eq to basically 0, and cut the bass to about 10:00 oclock, with the low and high mids basically flat. The AC2 tames the Underwood somewhat, and I find that I can bring back some treble. I ended up using the 'Jumbo' setting on the pedal, with Body and Top set to 12:00, and the level at about 2:00, which matched volume with the pickup when I bypassed the pedal.
There's a lot to play with here. I find I'm just getting a warmer tone with less effort. It doesn't necessarily sound 'acoustic' like a mic, but it does get closer than just the Underwood. I am liking this sound.
Another bonus, for me, is that a lot of gigs I've been playing lately have just been me going direct to the PA. In one of the rooms the soundman somehow wasn't getting enough signal from me. The pedal has a level control, which might help in this situation.
I plan to experiment with a Full Circle, and possibly with a mic as well in the future, either of which might just render this pedal redundant. But for now, I'm digging this quite a bit.
Cheers