[sdiy] *EXT* Re: Becoming better at understanding difficult analog schematics

[rburnett at richieburnett.co.uk]

You can set the maximum time-step of the simulation to something like 
2us and save the WAV file at a high sample rate like 192kHz.  Then load 
that into an audio editor, band-limit to 20kHz and resample to 48kHz 
before saving.  I find that gives better results for simulations that 
exhibit an inherently "high-pass" response like hi-hats, etc.  (Another 
thing that helps is to follow the circuit being simulated with a basic 
1st or 2nd-order 20kHz low-pass RC filter before writing the waveform 
out to a WAV file.  This curtails some of the ultrasonic stuff so it 
aliases less in the WAV file.)

Good VA has a lot in common with Spice simulations, but it has to be a 
bit cleverer to render in real-time and to handle things like 
non-linearities and discontinuities in a way that doesn't result in 
unacceptable levels of aliasing in the final audio output.

Being able to export simulation results to WAV audio files is still a 
neat feature though, aliasing and all!

-Richie,



> Very useful for prototyping, but it's aliasing like crazy if you
> produce rapidly changing signals like cymbals etc. The simulations are
> neither band-limited nor having constant timesteps. Virtual analog
> synthesis is something else. :-)
> 
> /mr
> 
>>