Covox Board – 8 Bit Audio not only for Legacy Computers

The 80’s called: they want their audio back…

That’s what happens when you’re drinking a few beers and being in a nostalgic mood: Already over a year ago I had designed a generic Covox Breakout Board (Wikipedia link) based on an old well established design.

Covox Board PCB

The whole design is based on two TTL ICs (74HCT373 and 74HCT164) and an R-2R resistor ladder (7.5k and 15k Ohm). The result is a simple DAC with 8 bit parallel and serial input and a few control pins. I’ve uploaded the PCB (back then I still used Eagle Cad) and the Gerber files to my Github Covox Repository.

Sure, I could have taken a cheap audio DAC, address it for example via SPI, and let the dedicated chip do all the heavy lifting. But that would not have been half of the fun of designing the board and (bit)banging the audio signal… 😉

The design is pretty generic and when I built it I thought I could use it in combination with a Sharp PC to generate audio output. I started with a few lines of code, but in the mean time other private tasks became more important. So I’ve reduced my testing of the Covox card to connecting it to an Arduino board and output simple (square and saw tooth) waveforms on my oscilloscope. Maybe if there is enough interest I will try to create a video with some mod-tracker like audio output…