I built my first computer in 1976 using an 8080 and an evolution of operating systems starting with a a home-grown system similar to the Digital Equipment Corporation ODT (octal debugging tool). I added cassette tapes and moved to a Sol-20 "cuter" tape system and a DIY 40 column printer. Then I added 8" DSDD floppy disks and the CPM operating system. I added the General Instruments AY-3-8910 programmable sound generator IC to the system for my audio effects. Here is a photo of my 8080 system before the upgrade to floppy disks and CPM.
I never did experiment with the SN76477 Complex Sound Generator so was interested in building this SN-Voice PCB that was sent to me to evaluate. I used cut tape 2N3904s for my expo converter and epoxied them together with a 2K tempco resistor.
This is my 3U MOTM-style panel design for this fully featured module. The mixer and EG switches are 1P3T. I used NKK for the flatted handle to match my other modules. The panel is a FrontPanelExpress with legend printing instead of engraving which was about a 50% cost savings. The white legends are more like a light gray in color.
The top controls have limited clearance to the edge so 12 mm potentiometers are used as well as a small (and expensive) Grayhill 3 position switch (Mouser 706-56A36-01-1-03S) for the LFO range. The switch has a 1/8" shaft so it requires a different (and expensive) knob (Mouser 506-PKES60B1/8).