The Ensoniq 5503 DOC chip is the son of the Commodore MOS 6581 SID chip. They were both designed by Bob Yannes. There's some documentation at:
http://www.buchty.net/ensoniq/5503.htmlBoth chips use 24 bit phase accumulating oscillators and 16 bit frequency registers. The 6581 SID chip has three of these oscillators and a state variable filter on chip, as well as a bunch of other stuff (envelope generators, VCAs, analogue switches). All waveforms are generated on chip using the phase accumulating oscillator bits, XOR gates and comparators, to produce sawtooth waves, triangle waves, pulse waves, ring modulation and oscillator sync.
Whereas the 5503 DOC provides a single phase accumulating oscillator, multiplexed up to 32 times. It uses a wavetable ROM or RAM for arbitrary waveforms, and has VCAs on chip, but no envelope generators or filters. It can do oscillator sync and a form of ring modulation (using the output of one oscillator to control the VCA of another oscillator), but all filtering and envelope generation is done off chip. The clue is in the name; whereas the 6581 is the Sound Interface Device, the 5503 is the Digital Oscillator Circuit/Chip.
Comparing the Poly 800 and the ESQ-1, the Poly 800 has simple waveforms, one or two oscillators per voice and a single filter for all four or eight voices. Whereas the ESQ-1 has a lot of different waveforms, three oscillators per voice and a filter for each voice (8 voices). But the single filter of the Poly 800 (Korg NJM-2069), to my ears, sounds a lot better than the filters of the CEM3379 chips in the ESQ-1.
The Mirage, ESQ-1 and SQ-80 provide you with good tools for exploring the DOC chip, especially the ESQ-1. I'd skip the Apple II and just get an ESQ-1. If you want a polyphonic synthesizer with sampled waveforms and an NJM-2069 filter per voice (8 voices), that's the Korg DSS-1 sampler.
--- In korgpolyex@yahoogroups.com, "bimmerfan222" <bperkins211@...> wrote:
>
> I dug a little more into the Ensoniq chip found in ESQ-1's and Apple IIGS's.
>
> Very cool chip!
>
>
> Here's a link to Apple IIGS Docs.. specifically the Hardware Ref. Guide (Sound docs start at pg. 101)
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> http://www.classiccmp.org/cini/pdf/Apple/Apple%20IIgs%20Hardware%20Reference%20Guide.pdf
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> and the Schematics.
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> http://www.classiccmp.org/cini/pdf/Apple/Apple%20IIgs%20schematic.pdf
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> (Above file's root page)
> http://www.classiccmp.org/cini/systems.htm
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>
>
> Seems simple enough at the core. It uses wavetables you program. Volume is also controlled via bit values.
> They show using 64K of RAM, but I think it's expandable.
> It has support for sampling as well.
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> 32 independent osc.'s total.
> Up to 8 independent channels via an ext. demux to split osc.'s out. So 8 independent voices in all is possible, or 4 stereo channels.. whatever you prefer to do, I guess.
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> I'm sure with the right coding, you can split the keyboard/voices up for multitimbral applications.
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>
> Nice chip, but it'll be about $50 USD to buy an old Apple IIGS to scavenge the Ensoniq chip out of.. or cheaper if you're lucky.
> But nice thing is that IIGS's are for sale all the time on theBay.
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>
> Even if it's not a good candidate to add/re-voice a Poly800, the programming methods are nice to study.. like I found it interesting that they mention there are no actual OSC's.. the OSC's are actually independent registers altered by the data.
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> The Apple Docs are just about the only published docs avail. for this chip since Ensoniq closely guarded their technology/software. But I know there are plenty of Ensoniq support sites out there to get even more info and perhaps code from.
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>
> Cheers,
> -Blaine
>