When I was in high school in the late 1970's, I did a digital recording/playback science fair project. It was displayed at a local mall, in Woodland Hills. I had a homebrew 6502 computer and I used an early 8 bit ADC and a simple resistor ladder DAC. I sampled at a pretty low rate, around 5kHz as I recall, so I could only record voice and only for a few seconds. But it was still pretty cool and my table got a lot of traffic.

Later, after starting work for Data General, I remeber thinking I could record a whole album in high resolution on a DG Zebra 50Mb disk drive. Not very portable though, they were the size of washing machines.