Emulating the TR-909(808) clap in detail

[Oden]

I still have this old project of an attempt at emulating the TR-909. Unfortunately, the information on how the original unit produced the sound ranges from incomplete to downright wrong. As such the thread is more a question regarding how the unit worked than an actual sound design question.

The basic idea of the clap is very simple, run white noise through a band pass filter and an envelope that triggers four times in rapid succession, with each repeat roughly 11ms apart. The devil as they say, is in the details.

The block diagram:


Disregarding the fact that the noise generator is outside the picture's borders, It's still obvious that the signal chain alone in fact won't produce the TR-909 clap sound as the "reverb" is not detailed at all. So, how did the original unit produce the reverb that tails the sound?

In addition, it would be nice if someone could help me calculate the cut-off and Q of the band-pass filter. The schematic is the following:



My calculation yields the result that the cutoff is at 1140 hz and the Q is 1.95. Not sure whether it's correct...

[philnsicab]

Hi, I am also interested in this topic. Here is a video where the 808 clap seems closely enough recreated with the Dave Smith Tempest. The key seems the noise used is a "resonant 4k noise" pitched down a little bit. The rest is pretty common.


The tempest manual mentions this "resonant 4k noise", alongside some other samples like the "resonant k".
https://www.sequential.com/downloads/te ... al_1.3.pdf
I would really appreciate it if someone could provide a hint how to create such a "resonant 4k noise".

I guess the 909 clap is just different from the 808 by the number of incidences of claps and how fast their occur. And I think the character has someting to do the noise.
In the 909 service manual, they say about the noise : "This is a quasi-random noise generator having two shift registers (IC32, IC33) connected in cascade making up 32 stages. Chaining of 32 stages provides a longer interval between the beginning and the end of shift cycles. This means that the frequency changes occuring at end/start points of shifting cycle are made less noticeable to the human ear. Two Ex-OR gates of IC31 clock the shift registers at a higher frequency, allowing them to create noises that contain favorable higher frequency contents. On power-up, a trigger is applied into pin 1 of IC32 via D48 for starting running" http://www.synthfool.com/docs/Roland/TR ... manual.pdf

For reference, here is the tr808 manual. The clap hand generating cycle is clearly detailled.
http://www.synthfool.com/docs/Roland/TR ... manual.pdf

[philnsicab]

I made a tutorial using the VST plugin RC-808 by Analog Mafia :

[philnsicab]

And the 909 clap :

[CinningBao]

Excellent work! Had that plugin when it first came out but didn't spend enough time with it.
Looks like I need to give it some more of my time!
This is exactly the kind of sound design tutorial needed for the RC-808.