[sdiy] DSP 808 new demo

rburnett at richieburnett.co.uk rburnett at richieburnett.co.uk
Wed Jul 24 11:58:02 CEST 2013

Hi Nick,

> Sorry if you already mentioned this, but...   Have you allowed for
> automation of the sound parameters?  Are the sounds altered in menus
> via the LCD?  Are you able to store different kits?
> Nick

This is one of the things that's still kind of up in the air at the 

All of the sound models are parameterised so you can theoretically 
adjust any cutoff frequency, decay, oscillator tuning, whatever...  
At present I just put 6 analogue pots on the development board and have 
them hard-coded to edit six fixed parameters for demonstration purposes: 
Bass Drum decay, Snare Drum Tuning, Snare Drum Snappy Decay, Hand Clap 
Decay, Cow Bell filter cutoff and Tambourine tuning.  At the moment no 
information is displayed on the LCD when these parameters are edited, 
and no MIDI CC data is currently transmitted.  (MIDI note on/off and 
realtime clock is currently implemented on transmit though, so it will 
play an external MIDI drum module when the sequencer is playing.)

I would ultimately like all parameter edits to transmit and receive 
midi CCs, and definitely to show briefly on the LCD.  No parameter 
automation will be done within this unit though.  i.e. You'd have to 
record your controller changes to an external sequencer.

The question really is the age old one of how to arrange the user 
interface.  I'm considering the following options:

1. Populate the panel with one analogue pot for ever adjustable 
parameter.  Looks great and is instantly tweakable, but is very 
expensive and heavy.  It's also quite a drain on the CPU scanning loads 
of pots, de-glitching the analogue levels, checking for changes and 
generating all the CCs etc.  Would probably need to add another low-cost 
micro to handle the UI.

2. Populate the panel with one pot for each of the original TR-808 
sound editing pots, and have all of the new additional sound parameters 
edited from a menu.

3. Stick a handful of pots along the top numbered say 1-6, and have 
them edit up to six of the parameters of whatever instrument you select 
for editing.  Not as immediate as one pot per function, but much 
cheaper, and better than a single pot and a deep parameter menu!  It 
also seems to work alright for things like the microKORG.

4. A single analogue pot, (or rotary encoder) and a long list of 
parameters, (like the alpha-juno.)  Definitely not as immediate and 
limited to tweaking one thing at a time, but much cheaper, and lower CPU 
load.  Not sure it's the right vibe for an analogue modelling product 

I'm happy to hear other's thought on this, either on list or via 
private email, as user interfaces tend to be something that people get 
passionate about!

Also thank you to all those who've replied to this thread.  It's great 
to get valuable feedback and suggestions.  I appreciate you taking the 

Best regards,


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