Thanks for the ideas and links!
After reviewing the PCM layout I could easily add more pins for 2 digital ins and 2 digital outs to allow for daisy-chaining AL3101/AL3102 DSP's (or to hook up additional ADC's or DAC's). It'd make the board wider by about 0.050" to 0.100" - no big deal.
I checked out the BatchPCB. I'd like to find someone to actually build the boards so I don't have to. Perhaps there's a cheap way to have someone flow the parts on a panalized PCB rather than individually solder?
Regarding the kits. I'd be fine with selling PCB's, pre-programmed ATtiny84's and the other parts without assembly/soldering if that's what you mean. Right now the work for me is in board assembly since the firmware for DSP control, program loading and pot value updating is pretty much done.
Not sure with what's up with Wavefront. They haven't changed that website for years. You might be right about using an AL3101 instead of a AL3102. I liked the AL3102 since it was smaller.
You could quote for example MyroPCB:http://www.myropcb.com/
They both produce PCB's and assemble them. I guess they can supply most of components as well (maybe the AL310x chips as well), and program the AVR. I have no experience with them but they claim to have a number of satisfied customers.
For stombox use the small size and limited number of IO's is fine, but on the other hand there are many more potential applications for with the DSP could be used like virtual analog synthesizers (you need larger MCU for handling MIDI and controlling the voice allocations and parameters, etc., and you need either MIDI UART of USB UART) and speaker crossovers (digital S/PDIF input would be nice, and for basic 2 way speakers you'll need at least 4 ch DAC outs, with subwoofer 6 ch DAC would be better). So it would be a good idea to fit some extra pin headers there so that you could for an example leave the tiny AVR out an use some external MCU kit to interface. On the other hand if you make the board much bigger like use four AL3101 chips on 6-bit parallel bus with some bigger CPU (like Coldfire or some ARM, an example is the Alesis ION/Micron, see http://www.statikcatstudio.com/ION-Q01-SCHEMATICS.pdf
) the product would become too expensive in small quantities. Besides if you need more processing power than AL3102 then it would be better to choose some other DSP.
Anyway what you have planned is fine, problem is letting people know your product, and maybe have the features they need added (if the space and costs will allow). There are some other forums like electro-music.com, prodigy-pro.com/diy and diyaudio.com where could be folks interested on what you are doing. Also regarding the software, the Python solution is fine for people who are coders themself, but for other folks some kind of Axoris or even Faust (http://sourceforge.net/projects/faudiostream/
) kind of environment would be easier. Guess it's easy in Python to expand the framework to include using some upper lever building blocks (library of preprogrammed DSP functions) that could be used to make an assembly (at work we use Robot testing framework such way, see http://code.google.com/p/robotframework/