OFF: Audio Generators

[Doug Pearson]

I've posted on this in the not-too-distant past, but I'm *always* up for
expounding on analog musical electronics ...

On Mon, 25 Jun 2001 18:48:19 -0400, Alastair Lee Sumner
<als at POSTMASTER.CO.UK> wrote:
>Hi folks, can someone explain to me exactly what an audio generator is?

Exactly what the name says: an electronic device that generates an audio
signal (that is to say, a periodic wave in the range of approximately 20Hz
to 20kHz, the range of human hearing).

>The type used in the old days by Hawkwind.

DikMik used equipment from his job as a TV/radio repairman.

>I've always wanted to know. I know
>about synthesisers but nothing about electronics.

The main components of a synthesizer (of the analog variety) are: VCO
(voltage-controller oscillator - the tone generator), VCF (voltage-
controlled filter - controls the timbre, or brightness, of the tone), and
VCA (voltage-controlled amplifier - sets the output volume or loudness of
the synthesizer).

An audio generator is a VCO without the other two parts (although it may
have a volume control); the important thing is that it has a knob to set or
sweep the output frequency (a synthesizer's "coarse tuning" knob would have
the same effect, as would the pitch bend wheel IF the pitch wheel can be
set to span several octaves - ideally all 10 audio range octaves).
Twisting the knob gives you those wonderful DikMik sounds (especially if
you run the output through a delay unit, especially an old tape delay like
the WEM Copicat [the model that DikMik used]).

>Is it possible to buy one
>ready made or would you have to build it?

Yes, you can buy audio generators; they're a standard piece of test
equipment.  Most electronic equipment dealers would carry several models.
In the UK, try Farnell; in the US, Mouser or Allied.

However, many (all?) modern audio generators have only digital controls,
with little buttons or switches to set the frequency, and no actual
frequency *knob*, which makes them useless as musical instruments (in the
Hawkwind sense).  You may have better luck checking out any surplus
electronic equipment shops, or even asking places that do TV/radio repair
if they have any old, obselete test equipment.

However, my audio generator has been permanently relegated to the workbench
(except for the time a friend took it across Europe on tour) ever since I
got a Triwave Picogenerator:
http://members.rotfl.com/soundshimmer/triwave.html

Not one, but TWO independent VCO's, AND three LFO's (low-frequency
oscillators) to modulate them.  Any non-musician can create HOURS of
unique, shifting tones with one of these, and easily figure out how to make
many of DikMik's (and Del's) classic Hawkwind sounds.  Again, a delay unit
(tape, analog, digital - it's ALL good!) only adds to the fun!  On top of
that, it's barely larger than the average guitar FX pedal (unfortunately,
the inside is too full of electronics to fit batteries, so you'll still
need a power connection).  Mine has been used on several albums and gone
across the USA on tour.

    -Doug
     jasret at mindspring.com