[sdiy] Envelope attack smoothing for drum question

Mattias Rickardsson mr at analogue.org
Fri Aug 21 23:26:55 CEST 2020


Hi Jason,

On Fri, 21 Aug 2020 at 22:39, Jason Nanna <jasonnanna at gmail.com> wrote:

> 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.
>

It would probably work, but would introduce undefined delays instead. For a
boomy 55 Hz bass drum there could be anywhere between 0 and 9 ms delay,
which I'd expect to be audible and untight...?

/mr



>
> 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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>>>>>
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