If you're reading this, you probably already know all about the Doubler, but if not, it is a very smartly designed "Swiss Army Knife" amp for double bass, and it sounds very nice with electric bass too. It is a great sounding, uncolored unit with ample power. Feature-wise, I've found the mic in, phantom power, notch filter and phase control to be extremely useful, as well as the footswitch-activated channel switching for upright/electric gigs. The two channels also work great for combining a mic and pickup. Last but not least, the extremely compact size and light weight (10.75" x 6.5" x 2.25", just under 3 lbs.) make it a no-brainer for travel or grab-and-go gigs.
I haven't been using the amp very much since I simplified my setup, so I'd like to pass it on to someone who will get some good use out of it.
The amp is in flawless condition, cosmetically and operationally. I did replace the rubber feet with similar size stick-on ones, as the original grommet-attached feet kept popping out. I have the manual, which I will of course include with the amp. $575 firm shipped within the continental US.
I'll knock off $15 for local pickup (I'm in S. Orange County, CA)