[sdiy] Wikipedia DCO article

[Bob Weigel]

Yup I'd just glanced at the schematics to refresh my memory on the 
Rolands.  The outputs of the op amps that get pulsed by the 8253's or 
whatever go to 4051 mux that is a 'self-adjust' of some kind.  Not sure 
exactly what that does since the digital circuitry obviously isn't 
guessing about whether it's hitting the right pitch :-).  Is it looking 
for incorrect ramp angle or?  I've never had to deal with that aspect of 
them. -bob

Scott Nordlund wrote:

>The MKS30 and JX3P (and JX8P, JX10P, MKS70) use the same basic idea as
>the Juno 6/60/106 (the Alpha Juno models are different) of a
>voltage-controlled ramp reset by a clock, but with some added oscillator to oscillator modulation.  
>
>
>
>The Bit 01 (and I'd assume the others in the series) use the binary-weighted output of a 4-bit counter to make a "fake saw", then a standard comparator to make the square/pulse wave.  The pulsewidth is adjustable, but not continuously (hmm, looks like there's room for a "really strange sounding PWM" mod).
>
>The Poly 61 uses the Juno/JX method for one oscillator and a "fake saw" (like Poly 800?) on the other.
>
>
>
>I checked the schematics just now...
>
>----------------------------------------
>  
>
>>Date: Mon, 12 Jan 2009 21:57:05 -0700
>>From: sounddoctorin at imt.net
>>To: david.k.cornutt at boeing.com
>>Subject: Re: [sdiy] Wikipedia DCO article
>>CC: synth-diy at dropmix.xs4all.nl
>>
>>Oh I see what you mean. Yea I was thinking of the latter synths there
>>and I did gramatically group them. I was thinking people probably
>>associated a *type* of synth with 'Juno' and I was noting how this new
>>series appeared the same year and THESE had the cpu driven
>>waveforms...I'll make it more clear. The MKS30 and JX3P are timer as I
>>recall along with the SX Kawai's, the Bit series and..maybe the poly61
>>too...can't recall.
>>
>>Cornutt, David K wrote:
>>
>>    
>>
>>>Nice work, Tom. One thing: The second-to-last paragraph
>>>of the "Historical" section implies that the Juno-106 uses
>>>the high-frequency pulse shaping method. In fact, all of
>>>Juno-6, 60, and 106 use the same DCO design -- a ramp core
>>>with reset pulses from a digital counter, controlled by the
>>>microprocessor. I'm a bit sensitive to this because I keep
>>>seeing people claim that the 106 is vastly different in
>>>design from the 60, and it really isn't.
>>>
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>>>
>>>      
>>>
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