[sdiy] DIY Analogue Drum Machines???

[Metrophage]

HI Jesse,

Not at all a silly question. DIY drum machines are incredibly fun. If
you don't go too wild then they are usually far easier to make than
ordinary synths and keyboards. You don't need 1v/octave control, you
can get by with far simpler envelopes. So far as the drum synth part is
concerned, you can find many great examples out there. I have tinkered
with the DR-110 , KPR77, and Tama TS boxes a bit, the sounds are fairly
easy to understand. Make a noise source, a simple filter, a pitch
envelope, an amplitude envelope - put a trigger through there and
enjoy. Even twin-t oscillators can be great fun. EPROM-type drum
machines I think are less interesting, but they have their moments.

Almost all drum machines have a digital memory, which is very handy. I
have not really gotten involved with computer firmware yet, but I have
breadboarded a basic drum machine with twin-t's and 4017 decade
counters configured as trigger sequencers. Making this type of drum
machine is simple, but can require a lot of hardware. Still, you can
add many features which are not present in any commercial drum
machines.

Picture six sixteen-step sequencers, each with a toggle switch and LED.
Each sequencer can be run at its own tempo, backwards or forwards, with
a selectable number of steps. Simple, yes? And in my opinion more
versatile than most any dedicated drum machine. Of course, this
requires at least 96 toggle switches, a big panel with costly hardware.
For drum voices you could make a bunch of tunable oscillators with
envelopes. There are a lot of circuits out there based of the X0X boxes
and such, for example. To simplify the sequencer one could replace the
toggle switches with momentary pushbuttons which activate CMOS
switches, and some form of memory. Then one could save patterns, or at
least switch between them.

The only drawback is, as I was saying, unless you use a microprocessor
- you need a lot of switches. I think TomG made a drum machine with DIP
switches for programming, which reduced the size and cost. If you
really play it though, you might be better off with good toggles. If
you already have a drum machine or sequencer, you can experiment with
making your own circuits of drum sounds, and firing them from the
ready-made sequencer.

CJ

--- Jesse Yoder <jojomanee at gmail.com> wrote:

> This may be a silly question, but I've been wondering lately if it is
> practical to build a DIY drum machine.  It seems like at the least a
> fun idea to mess around with.  However, I'm kinda new to the whole
> synth thing, so I dunno.  Hope I'm not straying OT with this
> question.
>  It seems to me that an analogue drum machine is basically a synth of
> sorts, so ...
> 
> I'm curious.  Are there any circuits out there?  Has anyone toyed
> with
> the idea?  Has anyone built one/tried to, etc.
> 
> Curious in NC,
> ~~Ponyboy
> 
> 


		
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