[sdiy] Envelope attack smoothing for drum question

Jacob Watters jacobwatters at gmail.com
Fri Aug 21 22:31:50 CEST 2020


Right. The linearizing is for noise, but the trimpot is the important part
for thumping. I added the diode part to my suggestion because it is a good
practice that I often see left out.

*Jacob Watters*
JacobWatters.com <http://jacobwatters.com/>
Tel: 226-886-3526


On Fri, Aug 21, 2020 at 3:52 PM Dakota Melin <dksynth at gmail.com> wrote:

> I think Jacob might be pointing out that if your VCA itself has DC offset
> problems that’ll thump as well.
>
> On Fri, Aug 21, 2020 at 3:41 PM Tom Wiltshire <tom at electricdruid.net>
> wrote:
>
>> How does use of the linearising diodes hep with the offset click?
>>
>> I agree about eliminating the offset as a source of the click, since if
>> the VCA thumps, it doesn’t;t matter what signal you feed it, or even if you
>> feed it no signal at all, you’ll still hear a click, but I don’t see what
>> the linearising diodes have to do with that.
>>
>> Tom
>>
>>
>>
>>
>> On 21 Aug 2020, at 20:25, Jacob Watters <jacobwatters at gmail.com> wrote:
>>
>> You mentioned an OTA based VCA. I have experienced some clicking with
>> these in the past. Use a linearizing diode and calibrate the 1k trimpot (
>> https://i.stack.imgur.com/5drhW.jpg). That will rule out the VCA as the
>> source of the click.
>>
>> *Jacob Watters*
>> JacobWatters.com <http://jacobwatters.com/>
>> Tel: 226-886-3526
>>
>>
>> On Wed, Aug 19, 2020 at 5:42 PM Didier Leplae via Synth-diy <
>> synth-diy at synth-diy.org> wrote:
>>
>>> 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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>>
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