[sdiy] DSP 808 new demo

[rburnett at richieburnett.co.uk]

Hi Damian,

Thanks for the kind words.

> Are you planning to release the code?

I'm not going to be releasing the source-code or HEX files.  This would 
just provide a quick route for someone else to knock out a product and 
make money out of my years of work.  It's also an open invite for a load 
of grief when people struggle to get it to run.  However, my long term 
view is to develop this, (and maybe other models I have,) into high 
quality pro-audio products.

> Are you going to make analog versions of your finger-snap, tambourine
> and laser-zap?

LOL!  I did breadboard an analogue tambourine and finger snap sound.  
The tambourine sound was actually modelled on the tambourine in one of 
the versions of Van Morrison's song "Brown Eyed Girl."  It's most 
prominent at about 2:45 only accompanied by bass guitar so was easy to 
isolate and analyse.  It's got two prominent formants at about 6kHz and 
8kHz, so all you need to do is pass white noise through two bandpass 
filters at about 6kHz and 8kHz with _really_ high Q factors, and apply 
an amplitude envelope.  It's actually easier to get well behaved high-Q 
digital filters than analogue ones because of component tolerances and 
drift.  You can also alter the tuning of the digital filters to take the 
formants up higher and get a polite sounding "miniature" tambourine 
sound, or lower them to get very festive sounding sleighbells!

Similarly the finger-snap has two prominent formants that are modelled 
by passing a few impulses through two bandpass filters.  Enveloped white 
noise is also passed through the filters to mimmic the lavish 
reverberation that normally accompanies this sound!

The zap sound is just a self-oscillating filter being swept downwards 
in frequency _really_ rapidly.  I tuned this sound based on what I heard 
in old electro hits from the likes of Afrika Bambaataa, Beasties, 
Egyptian Lover, etc, and what I could produce using my Roland SH-09.

Best regards,

-Richie,