[sdiy] More Digital VCO samples available

[Eric Brombaugh]

Paul Maddox wrote:
> I'm impressed that the aliasing isn't really noticable until quite 
> high in the frequency range, even on the sawtooth.
> This makes it a pretty usefull VCDO...

The other thing I've noticed is that the aliasing really only sounds 
like aliasing on frequency sweeps. When I use the DVCO with fixed 
frequencies (like with MIDI notes) the aliasing doesn't seem to resolve 
into discrete tones but rather just comes through as background fuzz.

The square-wave aliasing can be significantly reduced by clipping the 
filtered sine in the analog domain. That eliminates a lot of the edge 
jitter because the gentler slope of the sine's zero crossing gives more 
accurate timing. This suggests a use for the final op-amp stage that's 
currently languishing in the corner with nothing to do. Possibly another 
CV input for a comparison threshold and a clipped/PWM output?

>>  as well as a hard-sync sweep of the double-pulse which I think 
>> sounds pretty fscking awesome when played at high volume. Ian - that 
>> waveform was _made_ for hard sync.
>
> It does sound rather 'special'....

I'd never really played with syncing before this and it's interesting 
how it sounds more like resonance and/or formants on the frequency that 
drives the sync. This is really apparent on the sine sync. Now that I've 
learned what it's like, I've been able to identify it in some of the 
electronic music I listen to - Steve Roach seems to use it often in some 
of his more ambient stuff.

Eric