[sdiy] Variable rate waveform playback in NED synclavier

Dale Marvin dmarv at dop.com
Fri Aug 31 20:16:32 CEST 2012


On 8/31/2012 7:25 AM, Tom Wiltshire wrote:

>
> Going back to the voice diagram:
>
> 	http://www.500sound.com/SyncII/synthschem.jpg
>
> There's one bit I don't understand. On the left hand side of the diagram are the two Sample Rate Generators, which seem to take a clock signal Fclk and multiply it by a fraction N/M, where N and M are 8-bit numbers. How is this done? Doing arbitrary division is easy enough (just count M clock pulses) but how is the multiplication performed? Would it have to be a PLL with a divider in the feedback loop? This seems a bit dirty for NED. If not, how? I can't see how this bit works.
> Secondly, once this new sample rate is generated from the Fclk, it's fed to a Phase Angle Incrementer, which I take it is what we'd call an NCO. This seems to have a 8-bit frequency increment. So the final frequency is some weird combination of the variable sample rate Fclk*N/M and the freq inc - does this seem right or am I miles off here?
>
Go to this site <http://www.pat2pdf.org/>  and look up Patent 4554855.

This Flicker site has a large collection of high resolution pictures of 
many NED Boards:
<http://www.flickr.com/photos/krunkwerke/collections/72157622658834014/>
Lots of virtual reverse engineering here ...

Dale




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