I also wanted a multi channel midi-CV converter and could not find one that suited my budget. You won't find many 1-4 channel midi-cv converters for 90 USD and it was the easiest of the four modules to make. Roughly 8 easy hours. It works very well for my purposes. The 8 bit resolution is fine.

The module building was labour intensive. When one builds a one off synth, the labour is 10 times longer than what a business could do. Patience is key. You're getting very intimate with your synth and when (if?) you need to troubleshoot, you'll soon understand exactly how everything works. The kits are well documented and the support is first rate. I received replies to my questions within a day or two and when parts were missing and when panel paint was coming off (bad batch) I received replacements in days too. I added a homemade LFO and Polyvoks filter to the rack ears and built an Oakley soundsystems TB3031 above, using a piece of fluorescent orange perspex as a lid and running everything from one 1A 12V AC power supply. As said elswhere, the jacks provided are plastic and not rigid enough to conveniently pull in and out of the sockets, so I bought some metal ones which work nicely. Commented on earlier, some more mixing slots would be helpful. Instead I got creative with my patch cables, creating splitters and mixers there instead. They work fine on buffered inputs/outputs.

After all that work I was too tired to play the synth for a while! But how is it as a synth? Very nice. The dual filters are nice. Warm, drippy or agressive. Two filters are nice for formant sounds. The raw oscillators have a nice bite to them and the addition of a sine wave on Osc 1 is very nice. The VCA and EG does what it should. The prize for building the Paia is the certain quality that is hard to pin down with a real analogue. It appears these days that most are cynics. Still, I've noticed previously with other real analogues that when you run them into a delay box and get modulating, the effect is nearly always more pleasing than when a VA is used. I don't know why and the Paia is no exception here. I have big problems getting my VAs to generate sounds that I want to keep but with the Paia I find something every time. I like its spontaneity. Modulars incorporate the programming into the performance.

Gripes? All EG pots should be exponential, as the useful charge/discharge times are squashed into about 5 degrees. The EG attacks are also non retriggerable on a second note. I solved this for the AD EGs with a FET across the input to briefly discharge the capacitor when a new gate signal is present. This worked for the AD EGs but not the ADSR. Don't give the filter too high a CV at high resonance as you will blow your brains out with a sound from hell, no matter what the input signal level. I dread this, 2.00 am performing in my stage at Glastonbury. Amazing synth ambience and suddenly WARGHHHHH! Best be careful

This synth has a sweet feature set: MIDI control with velocity, bend, mod wheel, (re)trigger and gate, two VCOs, two multimode VCFs, three VCAs, three EGs (two ASR, one ADSR). There are no dedicated LFOs, though...you must use a VCO or an EG instead. The ability to have the EGs cycle is a very powerful feature that has uses way beyond LFO duties. The sound overall is very good but will not have you selling your vintage Moogs.

What's missing? It needs far more mixing capabilities (all you get is a single 2:1 mixer by using 2 of the 3 VCAs), some attenuators and some multiples to effectively route and scale control voltages. Since control routing is at the core of any modular's flexibility it's a bit of a shame that to fully utilize all that you get in the 4 base modules you really need to add extra modules!

There are two weak parts in the design. #1 is that at high gain settings (and that includes high resonance settings) the filters will break into unpleasant distortion. #2 is a lack of fine tuning adjustments for VCO pitch (the lone tuning control spans multiple octaves).

Still, if you have the skills to build the kits you can't buy a cheaper modular and it's a powerful synth despite it's shortcomings. With just the 4 base modules I've been able to patch it up as two separate monosynths (each on it's own MIDI channel), done complex FM on both the filter as well as the VCO and created shifting rhythmic drones controlled by cycling the EGs.

The very best thing about the 9700 system though is that it's FUN to use.

Short summary: Good, compact and cheap modular synth for the one willing to use a soldering iron. The sound could be described as very vintage, full bodied, and animated. The filters are a bit peculiar with high resonance.