If you want to play around with your own digital effects, you can now buy the general purpose box called Open Effects Project!
You can find it on Tindie.com
This can be programmed from Arduino and its core is a Teensy3.2. Then you can make your own audio engine in the graphical tool and then later on edit the code to adjust values on the fly.
Really nice tools from PJRC.com!
The schematic can be found HERE