Emulating the TR-909(808) clap in detail

How to make that sound...
219 posts since 30 Oct, 2010

Post Mon Jul 11, 2016 10:19 pm

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...

Return to “Sound Design”