[sdiy] TR-808 Kick Drum modelling explanation

[Jack Jackson]

That document is so delicious to read, it's like Ian Fritz's treaty on transistor matching.

Best Regards,
Jack Jackson


----------------------------------------
> From: rburnett at richieburnett.co.uk
> To: ol.gillet at gmail.com
> Date: Mon, 15 Jun 2015 20:58:51 +0100
> CC: Synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] TR-808 Kick Drum modelling explanation
>
>> Paragraph 8.2 is the most important ingredient :)
>
> Yes. I agree.
>
> Although their comments about leakage through R161 causing the pitch "sigh"
> are a bit misleading. It's really the current out of the collector of Q43
> due to reverse transistor action when Vcomm swings negative that contributes
> most to the higher pitch and brighter tone at the beginning of each 808 kick
> sound. They do talk about this effect too though.
>
> The first few cycles near the start of the bass-drum sinewave essentially
> slew downwards slightly faster than they slew upwards. This is what causes
> the pitch fall effect and introduces the harmonics that the 808 kick is
> known for.
>
> It's ironic that Roland's own Tr-8 still doesn't really model this properly.
>
> -Richie,
>
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