Oops-that "1Hz" should of course be "1kHz."
-----Original Message-----
From:Tkacs, Ken [mailto:
Ken.Tkacs@...]
Sent:Wednesday, October 06, 1999 8:19 AM
To:'
motm@onelist.com'
Subject:RE: RE: [motm] Anybody like Fixed filter
banks?(new mod)
From: "Tkacs, Ken" <
Ken.Tkacs@...>
Okay, here's the story (I've got the schematic right in
front of me):
The Moog 907 Fixed Filter Bank had ten controls. The first
knob was a
shelving filter marked "Low Pass" and the last "High Pass."
In between, the
resonant frequencies of the bandpass filters were labeled:
250Hz, 350Hz,
500Hz, 700Hz, 1Hz, 2 KHz, 2.8KHz, 14KHz. Some of those seem
strange, but
that's what the schematic says.
The input stage has a one-transistor amplifier, and the
output stage was a
two-transistor deal. The filter stages were all
poteniometer/2-inductors/3-capacitors/3-resistor deals.
Two of these ten-band (sic) filter banks were the core of
Wendy Carlos'
ten-band vocoder as first used ion her Beethoven's Ninth
Symphony, and soon
after in Timesteps, as heard in "A Clockwork Orange." She
had Moog give her
jack-access to the filters so that she could run the first
bank of separated
signals into envelope followers, and the ten from the second
FFB into VCAs.
When the former controlled the latter, she had a simple
vocoder.
Later, Moog produced the Model 914 FFB. The design was very
similar to the
former, but with 14 bands of resolution. Only "Lo Pass" and
"Hi Pass" are
marked on the schematic. I'm too tired to do the math to
figure out the
center frequencies of the bands.
Hope this helps.