[sdiy] Envelope attack smoothing for drum question

Jason Nanna jasonnanna at gmail.com
Fri Aug 21 22:38:33 CEST 2020


Would delaying the trigger until an oscillator zero-crossing be a simpler
way to synchronize?  Assuming a bipolar triangle, I don't think it matters
whether it's rising or falling.

On Fri, Aug 21, 2020 at 3:33 PM Jacob Watters <jacobwatters at gmail.com>
wrote:

> 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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