Casio CZ/ VZ/ FZ - Pro Series

> I wouldn't really think that it's an "additive square wave" synth.  
The Poly 
> 800 was a bit of a special case.  I'm pretty sure it used a sound chip 
> intended for arcade games.  I think the Siel DK 70 and DK 80 used the 
same 
> chip.

For your interest, Poly-800 uses KORG MSM5232 for DCO, and KORG NJM2069 
for VCF and VCA.
(See: http://www.asahi-net.or.jp/~wz4k-tnk/semi/poly800.html
It is a great site but written in Japanese.)

I opened my HT-3000 to compare the chips, and found what I believe to 
be the main circuit board. Besides the CPU PD78C10 and a memory chip, 
there was mysterious chips called MSM6294-03 and MSM6294-04, manifactured 
by OKI semiconductors. The name MSM is used by OKI, so KORG's chips may 
also be made by OKI. But I found no information on the net about these 
chips.

> Anyway what I'm getting at is while that arrangement could make the 
saw 
> wave, it couldn't make most other waves without being able to adjust 
the 
> phase and pulsewidth of each square wave independently.  Think about 
how you 
> would go about making a triangle wave out of just squares- one square 
wave 
> to get the basic shape of it, then add 2 different pulse waves, one 
25% duty 
> with a 90 degree phase shift, and one 75% duty with a 270 degree phase 
shift 
> (I think..) then more to refine it further.  I worked it out on paper 
but 
> I'm not really sure if I got that right or not.  At any rate what I'm 
> getting at is that it would be very difficult to get most waves this 
way.

I haven't thought of the possibility of creating triangle wave out of 
square waves. I don't know much about phase issues.
As mp3s on my site shows, HT's DCO can't generate such a soft-sounding 
wave like triangle. They produce so many variations of pulse and square 
waves.

'Additive square wave' synths may not be able to control phases and pulse 
width. I think the pulse widths are fixed to 50%. In fact, Poly-800 has 
no Pulse width parameters.
Poly-800's DCO and Roland's sub-oscillators generate square waves by 
'dividing' the master clock. So, the phases of each harmonics are always 
synced, I think.

> Seeing as how it has 16 steps, the saw wave looks more like it comes 
out of 
> a 4-bit DAC.  To me this would seem pretty likely.  It still doesn't 
explain 
> how the waveforms are made, and particularly why they're affected by 
the 
> amplitude envelope, but it makes some sense...

Yes, it may be. (Inspired by your comment, I thought that Poly-800 could 
be called a 4-bit synth.)
When I first saw the waveform displayed, I thought my HT might be a 4-
bit PD synth. But after a while, I came to think that PD needs at least 
8-bit DAC or so. So I'm confused again as to its synthesis engine...
I'm still rather for my 'additive square' hypothesis, but I'm not so 
certain about whether my HT has a ring modulator...

> I could look at the waves on my computer and try to get a better idea 
of 
> what's going on...

Further comments appreciated.


Best,
Sealed