SV: [sdiy] Mopho modulation DAC configuration, update rate, etc

[Tom Wiltshire]

On 6 Feb 2010, at 08:38, karl dalen wrote:
>
> Offcourse but there are basically no *modulation* frequency
> limit within the PA397, it can go into audio frequency range
> if one designs it in.

If the Mopho uses the same DCOs as the Prophet08, then I disagree,  
Karl. I might be wrong (happened lots before) but I don't see how you  
can do audio rate FM on a DCO.
Some people have argued that you can update the charging rate in the  
middle of a cycle without causing a glitch, by doing some  
recalculation of when the reset point would be, but I'm rather  
sceptical that it can be done accurately. And FM is the absolute  
worst-case, where you're changing the charging rate many thousands of  
times during a single cycle (48KHz sample rate would be a minimum for  
half decent FM). If you don't have some errors built up by the end of  
that, I'd be amazed.
Delighted, but also amazed.

Aside from the DCO, he's got an analog filter and VCA in there, so he  
can do audio FM on those, no problem.

T.