[sdiy] Waveform phases and hard sync, sawtooth vs. triangle?

Florian Anwander fanwander at mnet-online.de
Fri Jun 22 13:10:25 CEST 2018

Hi Mattias

Just two thoughts:

> When you make drum synthesis, FM synthesis or even some regular bass 
> sounds, it's often important that the oscillator(s) behaves 
> identically each time the sound is started.
If you start at the peak of the triangle, then you will have something 
like the overtones of a saw for the first half wave. This seems to be 
unwanted, but it corresponds to the sound behaviour of all physical 
drums. They all have a bright  attack sound when the stick hits the skin.
If you don't want this, then simply add something that acts like a VCA 
with an inverted decay envelope (like the autobend in the early Roland 
SH-synths), where the attacktime corresponds to the VCO frequency.

> You need a way to start the tri/sin at the zero crossing.

How do triangle core VCOs start after the power on? Is there a real 
reset function for triangle core VCOs? The sync-behaviour in the CEM3340 
simply switches the load/unload "direction" of the VCO-core. So it does 
not(!) do a reset, like the hard sync does in a saw core VCO.


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