Barberpoles and other things
gene.stopp at telematics.com
Sat Jan 17 00:09:00 CET 1998
It's interesting that you say that, Juergen.... "Klangumwandler" has a
nice ring to it. :)
To the American ear, a lot of German nouns seem to describe the object
they refer to in a very descriptive, almost humorous, way. For example,
"Klangumwandler" sounds a little like "Gong Warbler" or "Klang Wobbler"
or something which implies a thing that is both inharmonic and
constantly moving. Hence the name has a certain charm when applied to a
frequency shifter. (Sadly most of us over here have little or no
exposure to other languages, myself included.)
Anyway, here's a dump about various recent topics....
Central to any barberpole device (other than low-beat frequency shifters
and similar effects) is a multi-phase ramp-and-triangle CV generator. (I
think that the term "Shepard Function Generator" is the name for this,
right?) The ramps are used to control the rising effect (VCO, phaser,
VCF, etc.) and the triangles are used to fade in and out the audio for
each effect. I built one sometime last year, based on the schematics on
the PAIA web site. Before I built this one, I tossed a bunch of ideas
around in my head, like using some kind of CV processor similar to the
Electronotes Mulit-Phase Waveform Animator, or creating an octal current
source driving eight charging integrators with reset FETs driven by a
shift register, things like that. The PAIA design uses all digital logic
with a single multiplexed DAC driving sixteen sample-and-holds (eight
sawtooth, eight triangles). The project looked a little time-intensive
as far as building went, since I find that digital designs on
vectorboard usually have a lot of chips, but at the time I had access to
an Altera EPLD development station so I went ahead and stuck the whole
mess on a single PLCC chip. The DAC, VC clock, and S/H units were the
only external parts. It works fine, but I still have yet to put it
inside of a box or get any sounds with it (another darn rainy day
project). Does John Simonton still have PCB's for this? John?
BTW the Altera source and object files are long gone, so this is the
only one in existence :(
Regarding doppler-related noises - if you all ever get a chance to pick
up a Leslie speaker, do it! Assuming you have the room, of course. And
the AC power. They're pretty easy to modify for 1/4" unbalanced input,
and once you do that you can stick just about anything through it. Not
only do you get tube processing, but the acoustic properties are just
loads of fun. A Mellotron on slow chorus is a real thing of beauty.
Also Juergen, I for one would like to hear how people respond to your
DAT-hard disk-CD question.
From: Haible Juergen
To: analogue at hyperreal.org; synth-diy at mailhost.bpa.nl; Sean Costello
Subject: AW: Harald Bode Barberpole Phaser Questions
Date: Friday, January 16, 1998 3:41AM
> P.P.S. I love the term "Klangumwandler" for Frequency
It doesn't sound _that_ elegant to German ears, believe me.
"Sound converter" - this could be everything.
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