Hacker News new | ask | show | jobs
by lebuffon 1 day ago
In my case it was around 1975ish. There was no digital circuitry in signal paths then.

If you are asking how the thread pitch motor controller was working I have no in depth knowledge but it would likely be an analog envelope detector. (simple RC filter/integrator would suffice) That would be rectified to make a DC control voltage and the control voltage would be used to modulate the power to the motor in an inverse fashion. ( more audio signal -> less power )

No digits would be harmed in the process. :)