info-mac@utcsrgv.UUCP (info-mac) (07/12/84)
Date: Wed, 11 Jul 84 10:42 PST From: John Palevich <uw-beaver!palevich%atari.csnet@csnet-relay.arpa> To: info-mac@sumex-aim.arpa Subject: Macintosh Sound The sound is not sampled out of the horizontal deflection voltage. The 8-bit value is actually loaded into a counter, where it counts down during the horizontal line time, producing a variable duty-cycle square wave. This square wave is fed into an op-amp integrater to produce a variable voltage, which is, in turn, amplified and fed into the speaker. I sent a message out about all this a long time ago. I guess a bunch of new people have joined the list since then. . . . Jack Palevich [Ed. John's previous message on MACINTOSH sound is under <INFO-MAC>MACINTOSH.SOUND at SUMEX, available via ANONYMOUS Ftp.]