[sdiy] learning from early drum machines?

[Ingo Debus]

Am 11.01.2009 um 12:10 schrieb Dan Snazelle:

>> From: dayoldbread at ghettosynth.com
>> To: subjectivity at hotmail.com
>> Subject: Re: [sdiy] learning from early drum machines?
>> CC: synth-diy at dropmix.xs4all.nl
>>
>> Hi Dan,
>>
>> It's really quite easy to make beats without microprocessors. The  
>> earliest electronic drum machines used diode matrices as read only  
>> memory. You can replicate this approach or use a more modern  
>> variant like an eprom.
>>
>>
>> In essence, a counter cycles through memory and every place you  
>> want a beat you store a one which becomes a gate output.
>>
>> Think of a simple sequencer using a 4017 with reset after the 8th  
>> output. Each ouput then represents an eight note. Now think of the  
>> kick drum playing a 4/4 beat and you want an output on each  
>> quarter note. So you connect every other output to the anode of a  
>> small signal diode and tie all the cathodes toegether. You've just  
>> created a four input or gate. Now use the common cathode to  
>> trigger the gate input of your kick drum sound.
>>
>>
>> Repeat for each sound. What you end up with is a matrix of diodes  
>> where the anodes are connected to some gates and the cathods are  
>> tied together for each sound.

How about using a matrix of jacks? Each column represents a beat and  
each row represents an instrument. Connect the outputs of the 4017 to  
the columns and the trigger inputs of the sound circuits to the rows.  
Use jacks with diodes built in.

I'd provide at least 16 steps. Many rhythms have beats on the double- 
off-beat. I'd also provide a variable reset, at least at the 12th  
step, so rhythms with triplets can also be done.

Ingo