Agemixer (02:58:35)
but at that stage it is probably better to just buy a ready DAC or ADC chip that does most of that job automatically and.. less hassle and get cheaper perhaps

Agemixer (02:56:41)
and also schottkys at least to prevent line input or line outputs exceed or reverse peaks occur giving more than 5 v or less than 0 volts

Agemixer (02:55:17)
for tad more complexity, there could be a latch chip for inputs and outputs for digital signals buffered, but also some kind of output signal followers

Agemixer (02:53:06)
..to give it some line-level power, could be just be a simple bc547 transistor biased to center, and both input and output with a capacitor.

Agemixer (02:51:07)
always use capacitor in input and output lines of analog signal, you might also need a resistor (attenuator) for the final "line out" signal, could be resistor + trimmer/potentiometer of some lowish R value, so you might need a little preamp anyway

Agemixer (02:46:44)
then the driver code only needs to check, WHEN your ADC converter reached the level of the reference triangle signal (sample).

Agemixer (02:41:57)
..."which signal is higher": the (+) input drives the opamp output up to 5v, and (-) input pin drives it down to 0v.

Agemixer (02:40:20)
wire that result back to some PC or C64 port's input line, so that can notice when this input is toggled, then this triangle signal sample sent to the port is the actual sample value reached the same value OPAMP just does the comparison

Agemixer (02:35:11)
the output of this opamp gives the result, at "exactly at time" the value rised higher compared to o reference signal, giving out 0;or 5volts, "0" or "1" bit.

Agemixer (02:32:24)
add a simple OPAMP chip to your card board. Give the (+) pin the audio input signal and the "(-)" pin this reference signal.