Re: Sound Boards

[spec@vax2.concordia.ca (Mitchell Spector)]

In article Jeff Lemke <lemke@terra.cira.colostate.edu> writes...

>Can anybody give me a comparison of the sound capabilities of the
>Applied Engineering Phasor and the native sound capabilties of the IIgs?

The Phasor:

    Well the Phasor was an optional plug-in board designed for the
Apple II Plus and IIe (which had no sound capabilities built-in,
other than a speaker which could be toggled on/off to produce a
click or beep like PC's). It used 4 General Instrument AY-3-8913
sound chips, an SSI-263 speech chip (with the option of adding
a second) and had a built-in 4 watt amplifier which could output
in true stereo. There were DIP switches on the card which would
allow it to emulate other Apple II sound cards, such as the old
Mockingboard or Echo+ speech card (I was never able to get the
latter emulation to function).

    Each AY-3-8913 (identical to the AY-3-8910 as far as I know,
only it came in a smaller package) could produce 3 independant
voices, plus a 4th channel for a white noise generator. With all
the chips combined, that gave it 12 voices, 4 white noise channels
and 1 or 2 synthesized speech channels. The AY-3-8910 could be
used to produce sounds and music and was commonly used in old
arcade machines in the 80's (not to mention a couple of computers,
like the TI99/4a, Intellivision, Atari ST, etc). It was limited
though in that it could only produce sound using pre-calculated
waveforms (squarewave, sinewave, tringlewave and so on) so it
was rather artifical sounding. It was similar to IBM sound cards
like the AdLib and SoundBlaster, only those were much more
advanced and used FM synthesis.

The Apple IIgs:

    The IIgs came standard with a sound coprocessor chip built-in
every machine. That chip was the Ensoniq 5503 Digital Oscillator
Chip (Ensoniq DOC). It had 32 oscillators, which could either be
used independantly or paired with others to create richer sound.
The Apple IIgs paired them (with two reserved, for timing control
I believe) and had 15 voices. Some programs unpaired them to get
near 32 voices (e.g. Diversi-Tune) while others paired them twice
to get better sound (e.g. synthLAB, which has 7 voices). Unlike
the Phasor and other sound chips, the Ensoniq could do wavetable
synthesis. In otherwords, it could use an unlimited spectrum of
waveforms to create all sorts of sound variations and of course,
very realistic ones (you could digitize the sound of a real piano
or real violin as a basis for your waveform. Nothing exciting
today, but back in 1986 this was unheard of in a personal computer).

    The Ensoniq 5503 worked in 8-bit sound resolution, and could
play back at sampling rates up to 44.1 kHz and even _much_ higher
[I'll leave out any comments about the low pass filter as I'm a
little confused about it presently, as half the people out there
say it is bad, while the other half say its good. Oh, and no need
to repost those article clippings, Supertimer and Scott G. ;-)]
It had both a DAC and ADC built-in, so you could play back and
record digital sound recordings. It also had 8 independant stereo
channels through which each of the 32 oscillators could play
through, potentially giving the GS the ability to have stereo
sound came out of multiple speakers (sound in front, back, sides,
up and down). Unfortunately Apple wired all 8 channels into one
monorail channel through the 1/8" headphone jack, but they made
the signals available through a molex connector on the mainboard.
All existing third party stereo cards only decoded two channels,
so you only got left/right stereo, like most computers and home 
audio equipment today.

    In summary, while you could do interesting sound and speech
with the Phasor card, the Ensoniq chip in the IIgs complete blew
it away (as well as all other computers back in the 80's--and
most in the early 90's). The Ensoniq was a professional music
synthesizer chip, the same one used in the Mirage keyboard. It
could do everything the Phasor was capable of, including speech
synthesis, not to mention even emulate the Phasor's AY-3-8913
chips. Today its fairly obsolite compared with modern versions
of the Ensoniq and other wavetable chips and technologies (you
can see that if you try to use it to play MIDI files ;-) though
still quite impressive for a 12 year old machine! For example,
you can play 8 voice MOD files using a stock 2.6 MHz Apple IIgs 
as the chip acts as a coprocessor (the Macintosh Plus and SE, 
with its more powerful 68000 but lesser 4 channel DAC, cannot 
play MODs at all).

Mitchell Spector
spec@vax2.concordia.ca