Here's a 6 input mixer based on the Ray Wilson schematic at musicfromouterspace.com
This mixer works beautifully but the only hassle is that it needs a bipolar power supply. So while the Lunetta portion all runs on +5v the synth units need +-15v. So setting up an elegant power distribution thingy is going to be necessary.
Also built a wooden rack frame to house the bigger modules.
The more I rework the layout the more compact it gets, which is a good thing. Maybe it can be portable at some point.
The SN-Voice and Lunetta are close enough in amplitude to work with the mixer but the DS8s output woefully low levels. They will need their own little mixer and preamp. Good thing I know how to do it now!