Is there a way to output quadrphonic sound on a IIgs?
We all know that the “S” in GS stands for sound. Stereo cards abound but the GS is capable of much more. The following circuit uses the same technique as stereo cards to decode stereo but decodes quadrophonic. Inside the GS by the memory expansion slot exists the J-25 sound expansion connector that most stereo cards use. The pin outs are as follows: J-25 Connector 1 Analog to digital in (end nearest front of computer) 2 Analog ground 3 Waveform out 4 Channel address zero 5 Channel address one 6 Channel address strobe 7 Channel address two The analog in (pin 1) doesn’t concern us here. The waveform out is the important signal. The contains the output of all oscilators one after the other in quick succession (the DOC only handles one at a time). When the DOC is outputing the waveform from an oscilator it puts the channel address from the DOC register $A0 + osc (most significant four bits) on the three channel address lines and pulls the channel address strobe low. (The DOC realy has four
