[sdiy] Siel opera6 schematics

[Bob Weigel]

The wealth of information on these synths is on the DK600 link from the 
sounddoctorin.com global synth page.  I've worked extensively on these 
units and have included all the information I can accumulate on common 
problems and how the architecture works.  There are two analog 
oscillators.  "DCO" by definition means that there is some..digital 
element controlling the oscillations.  Had I been the one coining the 
terms I'd have made "DGO" (digitally generated oscillators) the case 
that would include ROM based waveforms (eg. Kawai K3, Korg DW series, 
etc.) and the Timer and CPU pulsing based things like Kawai SX series 
and Roland JX etc.  But it would ALSO include the Siel DK600/opera 6 
because what you really have here is an analog oscillator that is 
driving a TOS and divide down network!  (It's on those specialized 
chips..again consult my web page.)

Then there would be the DCO...digitially controlled oscillator.  
Well..hey anything with a tune feature that is digitally controlled 
would qualify for that in a way :-).    But it would be good to not use 
it for that since 'auto tune oscillators' is adequate for that 
classification.  But any kind of scheme which actually uses digitally 
generated control voltages rather than analog voltages to ultimately 
control the primary note value of the oscillator...that would be a DCO 
in any normal person's way of thinking.  So pretty much storage synth 
get gets the CV from a DAC...that would be a dco if I had been in charge 
of things.   I don't know why companies did what they did in that 
respect.  Marketing not listening to engineering?  I dunno. -bob

neil.johnson97 at ntlworld.com wrote:

>Hi,
>
>Scott Nordlund <gsn10 at hotmail.com> wrote: 
>  
>
>>Also, does anyone know if there's any merit to the "some have VCOs,
>>some have DCOs" rumor?  I've heard it multiple times but never seen
>>anything to confirm it.  All of them that I've seen use the same SSM
>>2031 VCOs with TMS3631 dividers.  The only changes I know of are front
>>panel/program button designs, different OS versions, and CPU boards
>>with a separate noise generator board.
>>If true VCO versions exist, they must be very rare.
>>    
>>
>
>The only schematics I've seen are those from S.Meyer's Siel website.  They _only_ show the HF-VCO + dividers architecture.  My guess is that since you can describe this as VCO or DCO they mixed up terms between different models depending on the market conditions..?  I think 12 SSM2031 VCOs would be very expensive, and quite rare.
>
>Perhaps there is some urban-myth going on regarding the VCO/DCO?  Possibly stirred up by the panel marking, which may well have said 'VCO' and 'DCO' at various times / different models.
>
>Unless someone has concrete proof either way..?
>
>Cheers,
>Neil
>
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