It's a very interesting article but yes, they need to lead with at least some youtube links to actual examples of what they're explaining otherwise you might as well just put up the PDF and nothing else.
In the 1990's I serviced computer printers and monitors. Juki made a daisy wheel printer called the 6100. It was unique in that it used mag-lev to suspend the print head.
It came to mind regarding this story because someone had written software to convert the Juki 6100 to a graphics printer, using the Period Key Only. It printed at 18 characters per second, try to imagine how slow that is.
Some years ago I actually owned a ZX Spectrum and I managed to run some demos on it loaded via my PC audio out. I'm still searching for that one great track it played.
In high school, I built a 1-bit sound board for the Sinclair ZX-80, programmed in machine code to play musically tuned delay loops for notes. This was inspired by noticing AM radio interference as sounds corresponding to program execution. Highlight was getting it to play “Yankee Doodle” for a science fair. Think I still have it in a box somewhere, will look.
I managed to get 8 octaves of tones out of a ZX-81 in my youth without any extra hardware. Bit banging the cassette port audio out and running that output into line in worked. Wasn't amazing and boring organ tone at best and would use a fair chunk of the CPU. But like most thinks was a case of fellow school friends boasting about their zx-spectrum with audio, one just don't take that sitting down.
It's not only the cheapo Sinclair Spectrum that had to make do with this "1-bit" sound, the much more expensive IBM PC didn't have better sound hardware "out of the box" either: https://en.wikipedia.org/wiki/PC_speaker
Because controlling timing of signals is easier than controlling level. You can take advantage of the fast and low-jitter clocks already made for digital electronics.
If you have a multi-bit DAC, it's difficult to made it linear. With a 1-bit DAC, it's much easier, because you only have two possible output values. And if you run it fast enough, you can apply a simple analog low-pass filter to the output and convert speed to bit-depth.
Pulse width modulation of the PC speaker was also a thing back in the 1990s. ModPlay under DOS could use the PC speaker as an output to play back Amiga MOD files, although it was very quiet. I ended up making a bunch of parallel port DACs in high school for friends so they could play MODs with a higher sound quality. Good times!
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[ 2.9 ms ] story [ 74.1 ms ] threadPretty impressive given the limitations, but not very pleasant compared to e.g. the C64 SID.
It sounded similar to this tune: https://youtu.be/QZnOd_f9YjQ?t=371
how i miss them!!!
No cellphones, no internet...
Hey Hey 16K
https://www.youtube.com/watch?v=-d8UfQn3BEg
https://youtu.be/u-D24A_N4d4
https://youtu.be/gXe51IsT2xs
They even scroll stars in the playback routine
https://www.youtube.com/watch?v=DSvj3Hjxiic
The 8088MPH demo also sounds surprisingly good.
https://www.youtube.com/watch?v=hNRO7lno_DM
If you have a multi-bit DAC, it's difficult to made it linear. With a 1-bit DAC, it's much easier, because you only have two possible output values. And if you run it fast enough, you can apply a simple analog low-pass filter to the output and convert speed to bit-depth.
I also had friends who owned a C64. Someday, a friend let me listen to another 1 bit sound that was produced by ..... the C64 diskdrive!
I was really flabbergasted by that hack!