Fun Project for Altair Clone Owners

[AltairClone]

"The Music System" was an innovative music package offered by a subdivision of Processor Technology (makers of the Sol-20) in the late 1970s. This system played three-voice music on the Sol-20, and with a bit of tweaking, on other S-100 machines as well. The hardware was an S-100 board (sort of) that required just three parts: 2 capacitors and a resistor. These parts formed a single pole low-pass filter and DC block of the final audio output. Software used the PINTE line on the S-100 bus (the interrupts enabled/disabled status line from the 8080) as a crude PWM to generate the audio.

In the real Altair, the PINTE line also drives the INTE LED on the front panel. Since the Altair Clone accurately drives the INTE LED on the front panel, the Clone effectively has an accessible PINTE line!

So... I built a tiny interface board with the 2 capacitors and one resistor, and tied the board into the INTE LED signal on the Altair Clone. I wrote the support functions the music software expects in system ROM (primarily console I/O), and voila - the Clone sounds just like my Sol-20!

Here's a quick video of the Clone playing "Lay Down Sally." Look closely at the INTE LED (upper left corner) and you can see its brightness changing in sync with the music.

http://altairclone.com/music.mov

I will soon put together a quick project so Clone owners duplicate what I've done.

Mike

[toml_12953]

I'm looking forward to it. The more things available for the Clone, the better! Thanks, Mike.

[Drunkle]

"Sounds" cool Mike. I to will be looking forward to seeing the final results.

[gio74]

wonderful, I love this

[gmh]

Just watched the YouTube video of this running on the Clone, it's great!

https://www.youtube.com/watch?v=HxYhjD-BYcA

[AltairClone]

Here's a link to the project page for playing music with the Altair Clone:

http://AltairClone.com/music_system.htm

There's enough information on the page to complete the project, but not a step-by-step recipe. You'll have more fun figuring out the details on your own :)

Mike

[Caterman]

Just thought you might like to see my efforts at a music system board.
Can't test it out as only just ordered my Altair 8800 clone ;-)

[gio74]

want one!!!