[sdiy] 808 drums...how they work?

Stewart Pye stewpye at optusnet.com.au
Tue Jul 14 23:22:21 CEST 2009

Hi Dan,

The pdf service manual  should be easy to find in a google search. It is 
very descriptive.
The  bass drum circuit will  show you how to get longer decays and pitch 
sweep. The toms will show you how to add a tuning control.
 From what I recall, if you want to trigger the drum sounds using an 
external trigger you can eliminate the trigger and accent transistors at 
the front of each circuit and feed a positive going pulse in. Something 
like the Midi to SDS would be good for this.


Florian Anwander wrote:
> Hi Dan
> I recommend the full service manual for the 808; it contains a 
> theoretical circuit description.
>> 1. Do these drums use resonator circuits
> yes (as far as they don't use noise)
>> 2, If they do, what excitation source do they use and how is IT 
>> created. ( what is an optimal excitation source,etc)
> Finally it is a trigger pulse coming from the coming from CPU, which 
> in detail consists from a not timing relevant signal for enabling the 
> individual instrument, an hi/lo voltage presenting the accent and 
> finally a master trigger which determines the length. For some 
> instruments it is filtered by simple passive RC-filters.
>> 3. if they are resonators, do they use feedback to allow for longer 
>> decays?  most resonators i have built have a very short decay so I am 
>> interested in finding ways of making nice, long, tones.
> Search for those tons of 808/606 modifications on the web.
> Florian
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