I'm currently working to implement a 3 voice synthesizer based on the ALF MC16 design.
It uses a 82c54 Timer (compatible to the 8253 on the ALF MC16) for the generation of the 3 voice frequencies as well as a TLC7226 quad DAC for the generation of the envelope control voltage (0-5V). Three CEM3396 dual oscillator "compete analog voice" chips are used for the generation of the actual sound. The CEM3396 has a logarithmic VCA control voltage (0-5V) input and several other CV (control voltages) for waveform, filter and linear gain. These additional inputs cannot be directly controlled by the ALF-software. Therefore I have to use potentiometers to create the CV externally (may be software controllable in a later version of my card).
The current state of the card is:
10.08.2017: built 2nd prototype card after testing the digital circuitry on a separate board. Added 10 potentiometer for 0-5V CV on an external control board.
11.08.2017: First test with 1 voice was successful.
11.08.2017: 2nd voice added and corrected some grounding issues. ..had to repair some loose wires.
12.08.2017: accidentally shorted GND and 5V and had to rebuild some of the digital circuitry.
13.08.2017: analog part of the 2nd voice is functional but the digital part seems to have a bug around the 8254 Timer and I have to fix it to continue. There TCL7226 DAC works like intended.
The Prototype-board in the attachment will have 3 voices with only one of the 2 oscillators per voice active. After the card has been tested successfully I will design a PCB and create the 1st pre-production prototype. On this card I will add a circuit to access the 2nd oscillator on the CEM3396.
The simple diagram included shows the connection of the chips.