Back when CD players were new and trendy, I had a strong desire for a CD player with vari-speed playback. This was to avoid retuning the guitar when playing along with music CDs.
I collected together several pieces of broken CD players and put together my own design based around a Yamaha digital decoder chip. I had to connect on to it the DAC. I also implemented the control processor using a Hitachi 6803. The only hard part was the servos for the main and sled motors and for the focus and tracking controls. I made these from power opamps.
Later on I added an S/P-DIF output.
Rear left is the power supply, with the all important 3 volt transformer winding for the VCD display heater.
The rear-right board contains the DAC and buffer op-amps.
The middle board contains the servos and decoder chip.
The front board has the controller processor. The small card to the right of that contains RS232 level shifters for a computer connection for debugging and development.