[sdiy] Schmitz ADSR replace pots with CV control?

rburnett at richieburnett.co.uk rburnett at richieburnett.co.uk
Tue Nov 26 19:16:18 CET 2013


> On the PIC, as far as I remember most instructions can take 2-3
> cycles.

1 cycle for moves and calculations. 2 cycles for branches that flush the 
instruction pipeline.

> ...Because if you go over that, then your envelope will be
> hard-synced to a signal slower than 100 kHz, which will definitely be
> audible and will carry around with your audio signal.

Huh, where does this 100kHz figure come from?!?!?!  The envelope of 
every sound you hear on a CD, an MP3 player or your Radio/TV is sampled 
at 44.1kHz or 48kHz!  Are you trying to suggest that this is adversely 
audible in some way?

> Given that the
> envelope is most likely going to amplitude-modulate a signal, side
> bands will easily be pushed into the audible range.

Any sensible envelope has it's maximum rate of change limited to avoid 
the popping or clicking artifacts that you hear with "instant" attack or 
decay settings!

Tom's PIC envelope generator is perfectly sound as far as I can see.  
The digital section is followed by a high-order Bessel filter with 1kHz 
cutoff so the output signal is inherently band-limited :-)

-Richie,



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