When my old guitar processor died a couple of years ago, I did some surfing and discovered a lovely piece of equipment made by TC Electronics called a G-Natural Acoustic Guitar processor. "An aw-royt bit a' gee-ah," as Robert Graham would say.
If you're interested in electronics for acoustic instruments, you might be interested in the comments I made in for an on-line forum back in April of 2008.
I play in a full-time touring acoustic/roots band, and I've used the G-Natural for about 2 1/2 months now.
I'm very keen on it. Between it and the Beggs Duet pickup in my guitar, I can achieve quite a natural guitar sound. I've stored three basic variations - two for fingerpicking (one for bare fingers and one for fingerpicks) and and third for a nice, chunky sound for flat-pick strumming.
My only complaint is that a flange on one of the footswitches came loose after only a couple of days, meaning the switch itself disappeared into the box. With the help of an enterprising stage manager, a screwdrive and pair of needlenose, we managed to retreive it and re-secure it to, but it was a VERY tricky operation - it's almost impossible to get any grip on the flanges/rings that secure the switches to the face of the box. It has stayed put since, though. (note: as of Sept 09 it's never come loose again).
I've been really pleased with it. You do need the manual to figure out how to work with it; it's not intuitive, at least not to me. I really like the three-band fully parametric EQ. You have to know a little bit about sound to know what you're doing, but if you do you can really get a good sound dialed in. The boost function is excellent, and I like the fact that it's flexible - you can either set a universal boost level or a specific boost for each of your pre-set sounds.
I also like the fact that it will accept 100 to 250 Volts input; when we tour in the UK I can plug it straight into the wall same as here (here being Canada/US).
It's a terrifically flexible system, one consequence of which is that it's not necessarily easy to set up. Keep the manual with you on the road, though. Maybe it's just me, but when I want to go back and tweak something (a few weeks after the initial setup) the menus and scrolling etc., are just subtle enough that I can't always recall the procedures.