When I did my jazz gig last week, I wasn’t relying solely on my fingers and the bass to generate the required volume. I also used a small amp and microphone to give a boost. It did not feel incredibly effective but did help me hear myself a little better, although I was wary of feedback. I had been using a dynamic mic but decided on my Zoom H2 for the night.
One interesting side effect of using a recording device is that I also grabbed a recording of the sets, which gave me an opportunity to listen back to what it heard. The double bass sounded lovely but there was a lot of other sound picked up too. Despite only being a short distance from the bass, the mic is just too sensitive!
I had better carry on researching other options but perhaps I could apply some padding to hold it nearer the bass and also to reduce peripheral noise? It certainly seems like an interesting twist to not only pick up the sound but capture it as well for later analysis.