[sdiy] Envelope attack smoothing for drum question

[Mattias Rickardsson]

Hi there!

A smoothing of the envelope will likely not be slow enough to avoid your
problem for low frequencies, and will affect the sound too much. And the
drum hits will still be inconsistent when the oscillator is at random
phases.

Instead, not immediately simple but anyway:

Implement an oscillator sync mechanism that resets the triangle wave to its
center value and starts in a certain direction, so that it always starts in
the same way when the envelope is triggered.

It will likely not be obvious how to do this, but I've done it and I'm sure
it will be possible in your design too with quite few components. In a drum
synth it will be worth it! Unsynced oscillators are for string synths. ;-)

/mr


Den ons 19 aug. 2020 23:41Didier Leplae via Synth-diy <
synth-diy at synth-diy.org> skrev:

> We are working on an analog drum module that uses a simple envelope
> created from a trigger to control the amplitude of a triangle oscillator
> with a basic OTA based VCA.
>
> We are having a problem with a slight clicking sound at the beginning of
> many of the drum hits. We think this is because the attack of our envelope
> is so sharp that the beginning of our drum hit looks like a straight jump
> from 0V to wherever the triangle wave happens to fall. Therefore the click
> is somewhat random in that it doesn't occur when the triangle happens to be
> low at the time of attack.
>
> Can anyone suggest a simple way to deal with this, like adding a slight
> bit of attack time to the envelope? How could this be done without adding
> too many parts?
>
> Thanks,
>
> Didier
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