Sv: [sdiy] Digital VCO update

[Eric Brombaugh]

Paul Maddox wrote:
> firstly, well done on getting this going, I hope we'll get to see and 
> hear it in action sometime soon.

My intent is to get a board built (it's on a plugboard right now 
(Ahhh!)) and document it on a website. Hopefully within the next week or 
so time permitting. I plan pictures, schematics, source code, text 
description and possibly some short audio samples.

> I can't see a reason for not having one board, with two 'code' 
> downloads, one for VCO and one for VCLFO, then you just choose which 
> you want to run :-)

Well, yah, sorta. The DVCO will have a higher sample rate than the DLFO, 
so the reconstruction filter will have different corners. The lower 
sample rate gives me more time to compute high-res waveforms. My DVCO 
runs at 62.5kHz with filter cutoff at ~16kHz and really doesn't have 
time to do much more than lookup in a 256 sample table. The DLFO will 
probably run at 23kHz, with the filter cutoff at around 5kHz and can 
theoretically compute triangles and ramps that are accurate to 1 lsb 
(effectively a 2k table).

Also for some of the additional LFO features mentioned it would be 
really nice to have more digital I/O, so the DLFO might like to live in 
a 20-pin part.

Nonetheless, I'm building up the current circuit on perfboard right now, 
and while it's targeted at the DVCO application, I'll be using that 
board for the initial development of the DLFO too.

Good point though. Thanks for the feedback.

Eric