Hearn's - VIDIUM
|VIDIUM ( Analog xyz driver/ sequencer), 1969
||William Heam has been a Staff Scientist Engineer in
the Electronics Engineering Department at the Lawrence
Berkeley Laboratory, University of California. Educated
in engineering at Berkeley, he has been employed since
1973 in the Accelerator and Fusion Research Division at
LBL, where he was instrumental in the development of the
EDIT (Electron Beam Ion Trap), the Tandem, the Magnetic
Fusion Experiment, Real Time Systems and the Heavy Ion
Linear Accelerator. He has several patents issued in his
"I was a curator at the Exploratoriurn and I had designed a
really large console that made complex color lissaaous patterns:
multiple locked oscillators and pseudo-three dimensional shapes.
I always thought they were quite beautiful. They had been used in
a couple of different applications but I made a large console
that would generate great families of them.
I got the idea from somebody else in New York who had done it
long before me. I saw what he had done. I improved the deflection
amplifiers to give a really good response and I developed a
system of color modulation which I have a patent on. It painted
color on the surface according to the convolution of the surface.
The monochromatic versions were beautiful, very lacy and sharp.
They had a very sharp trace on the electromagnetic CRT. And if
you can deflect the beam, which is very difficult, you can get
beautiful patterns from voice or recorded music.
For color the basic trick is that the color is a function of the
velocity of the trace as it moves on the screen. As the trace
moves, the color stretches toward the red end ofthe spectrum. You
know what the spectrum looks like. It starts at red and goes
through orange, yellow. green. blue and then violet. I assigned
colors according to the actual velocity of the trace on the
screen. I had circuits which could measure the velocity and
change the color of the contours as it was moving. In doing that
it made the contours of the image stand out in a really
It's been many years since I've done a thing on it because it was
such a dead end. I found that it was quite interesting and
beautiful but it had no commercial application. People in special
effects, film or advertising all have very tried and true
techniques that they stick to. They don't want anybody coming in
and disturbing their nice game.
I paid for all of it myself up to the point where I got some
exposure, and a very wonderful man named A] Leavitt here in San
Francisco, who later turned out to be a kind of pain in the ass,
saw it. He loved it and he said we should exploit this. I said
fine and he made a contract with me through negotiations with my
attorney. We forined the Color Communications Corporation. Al put
in $30,000 and I put in my patent and then he died. I never would
have been able to do what I did if Al had lived. That's the funny
part of it. He died of a heart attack at the beginning of the
project and the money was in the bank and I went ahead and built
Through EAT I met a number of budding electronic music composers.
I helped them build music synthesizers and when I developed the
Vidium, they found that It was a really sympathetic way of
producing images directly from their signals to get a visual
synthesis of what they were doing sonically. Don Buchla came by
for a few meetings and I think David Tudor was very interested in
Don Buchla was the strongest influence I ever had in terms of the
way he did things. if you look at this you'll see that it's very
similar to his synthesizers in the philosophy of what it does:
control voltages. logic voltages, signal voltages and unshielded
banana jacks. so that you can stack them which makes the flow
much simpler. I think technically you can say that this machine
could have been designed by Don Buchla.
The people at Video Free America in Berkeley asked me to make a
colorizer for them: Arthur Ginsberg. Skip Sweeney and Alan
Shulman. They showed me that they had a colorizer but when they
opened it up all the parts fell out. It was a little thing in a
gray box about this big and it cost $800. It had two knobs on it
and made a smeary color. I said, "we can do better than
that." At that point I evolved the concept of the zone
colonizer to cut the gray scale into segments.
What I really lust after is to make machines that are so clear to
a creative person and gives them so many possibilities that they
can use them. It just gives me a terrific thrill when I see
someone like Ernie Gusella in New York who's doing truly creative
work with the Videolab." B.H.
VIDIUM "MK II"
is a hybrid analog synthesizer which acts as
a "hyper Lissajous pattern generator." Developed by
Bill Hearn in the early l970's, the Vidium was inspired by
earlier color X/Y display art and an exhibit called
"Sidebands" at the Exploratorium in San Francisco. The
fascination with animated color shapes driven from sound formed
the basis for Vidium. Numerous X/Y displays and audio function
generators were tried before arriving at the current form of the
MK II unit.
|The basic Lissajous pattern is generated through two
waveforms attached to an X/Y display screen (or
oscilloscope set in XY mode) with two sine waves driving
the horizontal and veitical deflection circuits. With the
X axis sinewave "in-phase" and the Y axis
"out-of-phase" a shape is seen on the display.
If the phase shift is 90 degrees, a circle is formed,
with 45 degrees an ellipse is seen, and with 0 degrees of
shifl a diagonal line is seen.
(Whereas the image to the right is
actual output from the Vidium, the four following images
were created by Jeffrey Siedler, to simulate the images one might create
on a VIDIUM-like device.)
||The Vidium drives each axis with independent
oscillators while inserting precise phase shifts and
modulation signals to create elaborate shapes. These are
expansions on the classic circle and figure eight pattern
appearing as "harmonically pinched doughnuts"
and vector textures of slowly changing form Programniable
waveforms of sinewaves shift into triangle waves, and
then into square waves to deflect the XY display beam,
forming sinuous curves and boundaries.
|A modified color television is used for the XY
display with the deflection yoke replaced with a new yoke
driven from audio amplffiers. The audio amp is in turn
driven from the main analog waveform generator rack.
Color is added by wiring to the color "hue
control", forming a voltage controlled phase
shifter, and wrapping, in phase, 540 degrees of the
normal 360 degree hue space. Color saturation and
brightness is set by the TV's front panel controls. A
special analog velocity/position detector calculates: the
square root (X squared plus Y squared) of the deflection
signals that feed the color hue shifter. A threshold
detector blanks the beam if the X and Y settles to zero.
This suppresses the beam of a stationary dot at the
center of the display, which can "burn out" the
screen phosphor. The hue shifter allows drawing of
textural surfaces in smoothly changing colors. The hue
shift tracks the shapes automatically.
|The main control box consists of two, 3 foot by 3
foot, racks mounted side by side. The left side contains
the "voltage sequencer" outputs with 60
multi-turn knobs called Helipots, while the right side of
the control rack contains the control and signal
||The main control of the synthesizer is an Analog
Voltage Sequcncer. 'The "sequenced voltage
source" has six controllable "steps", each
"gating ON" 10 voltages; the voltages set by
ten-turn potentiometers located on the left half of the
rack. This six by ten matrix of voltages is
interconnected through "Pomona Stacking Banana Plug
cords" to other modules located on the right half of
the rack. Commonly the sequencer is wired in a tandem
chain of modules: the first module triggers the second
module etc., until the sixth sequencer step is triggered.
An oscillator or button at the front end starts up the
chain of events. Each "step" has a time delay
(a monostable multivibrator), and a light bulb to
indicate that it has been triggered. Output jacks for OSC
START, SEQ OUT and EOS (end of sequence) are used to
connect to the next module in the sequencer chain.
|Control voltages are available on colored banana
jacks with RED representing analog outputs, BLUE for
analog inputs, BLACK for digital inputs and WHIE for
digital outputs. The digital output signals have a
"Wired-Or" property to tie multiple outputs
together with the lower voltage being the victor. The
Analog Voltage Sequencer can have its outputs tied
together due to its "bare-collector" output
stage. This allows the sequencer to "switch- on up
to ten voltages for each step in a sequence.
||The pattern generator side is built around basic
sinewaves and phase shifted sinewaves. The modules
consist of oscillator frequency sources and processing
modules. Multiple oscillators are present, including a
voltage controlled function generator. This allows for
voltage control of it's frequency and phase, and an
externai sync input. The output generates a collection of
wavefonns: triangle, square, sawtooth and sine, A digital
version of the "trigger out" and a waveform
triggered indicator, "logic out", are made
available on separate jacks. A more elaborate version was
proposed to allow voltage control of waveform shape: the
input voltage would shift the output waveform from sine
through triangle to square.
Another signal source is an envelope generator. A trigger
pulse, "ENV START ". starts a pulse output, and
"ENV STOP" turns off the pulse. The rise/fall time of
this pulse is voltage controlled and digital outputs indicate
that the envelope has triggered. The envelope pulse is combined
with the main oscillators to smoothly shape the underlying
Closely tied to the idea of Lissajous pattern generation is the
need for controlled phase shill of the sinewave signal. To
accommodate this, a modified "All-Pass" filter circuit
is available where the input signal is phase-shifted in response
to an external voltage control.
For processing of waveforms, a Voltage Controlled DC coupled
Amplifier is present, acting as a two quadrant multiplier with a
summing input stage. The amplifier sums together multiple inputs
while the voltage control input attenuates the summed result and
sends it to output. The control signal can come from the envelope
generator, the sequencer voltage or the oscillator waveform:
Output = ( ln_1 + ln_2 ) x Control.
A precision Four quadrant multiplier with two sets of inputs. A
and B with inverting and non-inverting polarities is used to
modulate the oscillator waveforms: Output = ( lN_A1 - In_A2 ) x (
In_B1 - In_B2). These four quadrants allow both attenuation and
inversion of input waveforms.
||The combination of the Voltage controlled summing
AMPs, with Four Quadrant multipliers and phase shifters.
allow the multiple oscillators, envelopes and knob
control voltages to mingle their signals into curious
patterns of X and Y signals. The hue shifis are closely
linked to the pattern drawn by the X and Y waveforms.
forming the unique interlocked VIDIUM Lissajous suifaces.
The front panel was constructed by Joshua Partridge and
the circuit boards were assembled and tested by Richard
Rhoda. Bill Hearn designed the detailed circuits and
originated the concept for VIDIUM. lIe holds a U.S.
patent based upon the color display subsystem titled
"Visual Display of Complex Color Television
Soundwave Signals", number 3,627,912. granted on
December 14, 1971 - J.S.
This page has been largely taken from ARS ELECTRONICA 1992.
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