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oblivion
January 14th, 2013, 04:40 PM
this is probibly a dumb question but what are the sound capabilities of the old compact macs? I cant find the information anywhere. i'm assumeing its just a "PC" speaker.

vwestlife
January 14th, 2013, 05:58 PM
this is probibly a dumb question but what are the sound capabilities of the old compact macs? I cant find the information anywhere. i'm assumeing its just a "PC" speaker.

Macintosh 128K, 512K, 512KE, Plus, SE, Classic, Classic II (Performa 200), Color Classic (Performa 250), Color Classic II (Performa 275): Monaural four-voice sound with 8-bit digital/analog conversion using 22-kHz sampling rate. Later models have a stereo output jack, although the sound capability is still only mono.

Macintosh SE/30: Apple Sound Chip (ASC) including four-voice, wavetable synthesis and stereo sampling generator. The built-in speaker is only mono, but if you connect external speakers you can get stereo sound.

oblivion
January 14th, 2013, 06:52 PM
awsome, thank you

Hatta
January 15th, 2013, 07:47 AM
Macintosh SE/30: Apple Sound Chip (ASC) including four-voice, wavetable synthesis and stereo sampling generator. The built-in speaker is only mono, but if you connect external speakers you can get stereo sound.


What would be good to demo the capabilities of this sound chip?

olePigeon
January 15th, 2013, 07:53 PM
Any old MIDI software would be cool.

Trixter
January 15th, 2013, 08:44 PM
Macintosh 128K, 512K, 512KE, Plus, SE, Classic, Classic II (Performa 200), Color Classic (Performa 250), Color Classic II (Performa 275): Monaural four-voice sound with 8-bit digital/analog conversion using 22-kHz sampling rate. Later models have a stereo output jack, although the sound capability is still only mono.

That's not entirely accurate. The design of the Mac allowed one sample output per scanline (http://www.folklore.org/StoryView.py?project=Macintosh&story=Sound_By_Monday.txt) (DMA retrieved a sound sample during the horizontal retrace), so the actual capability of the early Macs was a single voice. The four voices was done in software, so the system took a speed hit if you actually used more than one voice. Some software didn't use the system toolbox and did their own mixing; this is why you can play up to six simultaneous digital notes in Jam Session and Studio Session (they are doing the mixing themselves).

22KHz isn't quite right either, but most pages use that for convenience. Mac had 342 scanlines, so assuming the 512x342 B&W monitor ran at 60Hz, that works out to 342*59.97=20520Hz. I say "assuming" because I just spent 30 minutes trying to find the classic Mac's actual refresh rate and was unsuccessful. For "perfect" 22050Hz sound playback, the mac would need to drive the monitor at 64.4Hz which I find doubtful.

vwestlife
January 15th, 2013, 10:01 PM
According to http://www.bigmessowires.com/2011/08/ ...


Including the VBLANK region, the original Mac had 370 lines of video per frame. The audio hardware had a 370 byte sample buffer, and it’s not a coincidence that those numbers are the same. At the end of every horizontal video line, the hardware fetched a single byte from RAM and used it to update the audio DAC (which was not actually a DAC, but ignore that for a moment). Since the horizontal line rate was 22.2 kHz, this provided 8-bit 22.2 kHz audio. The contents of the audio buffer were played (output to the speaker) exactly once per frame.

Arcady
January 15th, 2013, 10:20 PM
I thought the refresh rate for the Mac Plus, SE, etc was 60.15 Hz.

Anyway, when they switched from using just the original ASC (Apple Sound Chip) to using the ASC and a pair of Sony chips for 8-bit 22kHz stereo, I didn't think video refresh was involved any more. That's why the SE/30 and all other Macs from then on were able to drive multiple displays at different resolutions and refresh rates. This same basic audio setup was used on the Mac II line and all of the rest of the Macs all the way until the Quadra 840AV and 660AV came out in like 1994.

Trixter
January 16th, 2013, 09:58 AM
According to http://www.bigmessowires.com/2011/08/ ...

Cool, thanks for the clarification. (I completely forgot about the vblank area, doh!)

To the OP: If you can find a copy of Studio Session or Jam Session, you should give it a run; it's a neat trick to perform 6-channel wavetable in software.