[sdiy] Digital VCO

[Eric Brombaugh]

Richard Wentk wrote:
> One way to do bandlimited waveforms is to precalculate them and select 
> them dynamically based on the frequency.
> Splicing can be an issue, but if you're working with a fairly low-res 
> DAC ultimate quality isn't such an issue.
True enough, and I might try that - especially since my exponential 
routines give me a nice octave indicator. The limiting factor here is 
that the low-end PSoC is somewhat limited on Flash space (only 4kB), so 
I can't do too many tables with that one. For a few cents more though 
its probably doable.
> Sounds like an interesting project. The big advantage with digital is 
> that it's trivially easy to turn a digital VCO into a digital VCLFO 
> with a cycle time that goes as low as you want.
Yes. The biggest problem with the LFO concept is that the aliasing 
starts to be fairly audible even on a sine waveform when the frequency 
gets below 60Hz or so. Longer & wider wave LUTs help with this though, 
so it might be pretty easy to fix.

Eric