Chiptunes on an ATtiny4 and the 3 Cent Micro

Re:Chiptunes on an ATtiny4 and the 3 Cent Micro by exDM69 on Tuesday May 04, 2021 @11:26AM (#27038602)

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

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Re:Chiptunes on an ATtiny4 and the 3 Cent Micro by 8bitsrule on Wednesday May 05, 2021 @01:26AM (#27046520)

A 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' ;-)

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Re:Chiptunes on an ATtiny4 and the 3 Cent Micro by exDM69 on Wednesday May 05, 2021 @06:20AM (#27048168)

Yes, 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.

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