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Yes, the legendary SID chip was a digital oscillator followed by an analog filter. After seeing this heroic SID chip reverse engineering (0), I tried building
by exDM69 5y ago
Yes, the legendary SID chip was a digital oscillator followed by an analog filter.
After seeing this heroic SID chip reverse engineering (0), I tried building the filter section using a quad opamp to make the state variable filter. It sounds kinda nice for such a simple circuit.
I've been planning a project of using a micro controller to do the oscillators and then use the PWM outputs to drive the filter control voltages.
(0) http://forum.6502.org/viewtopic.php?f=8&t=4150 http://forum.6502.org/viewtopic.php?f=8&t=4150
- 8bitsrule 5y agoA passive filter (if you've got the headroom) doesn't have to be fancy ... just a capacitor and variable resistor will let you custom-mellow the excess highs. (Old radios had these for 'tone control' ;-)
- exDM69 5y agoYes, a little low pass will make a square wave much more pleasant to the ear. But a proper LP/HP/BP resonant filter is almost a musical instrument in itself.