Moog Music Minimoog 204D Synthesizer
NO. OF SOUND SOURCES: 5 (3 Oscillators, 1 Noise Source, 1
External Input /Microphone Pre-
OSCILLATOR FREQUENCY: 0.1 to 20kHz (cycles/second) in six
SHORT TERM OSCILLATOR STABILITY: Better than 0.25%.
OSCILLATOR WAVEFORM OUTPUTS: Triangular, Sawtooth,
Triangular-Sawtooth Mix (Oscillators 1 and 2 only). Reverse
2 only), 3 widths of Rectangular.
NOISE SOURCE OUTPUTS: White or Pink random waveforms.
PREAMPLIFIER INPUT: 10 millivolts minimum; 2 volts maximum.
PREAMP INPUT IMPEDANCE: 100K ohms or
FILTER CHARACTERISTIC: Wide-range low-pass filter with
variable-height resonant peak at cut-off frequency, and
24dB/octave cutoff slope.
RANGE OF CUTOFF FREQUENCY: Continuously variable from 40Hz
to 20kHz (9 octaves).
VOLTAGE CONTROLLED AMPLIFIERS
NUMBER OF AMPLIFIERS: 2 (one controlled only by its Contour
Generator: the other controlled by optional external
DYNAMIC RANGE OF EACH AMPLIFIER: 80dB.
NUMBER OF CONTOUR GENERATORS: 2 (one controlling filter
through an attenuator; the other controlling the first
voltage Controlled Amplifier).
RANGE OF ATTACK TIME: 10 milliseconds to 10 seconds.
RANGE OF DECAY TIME: 10 milliseconds to 10 seconds.
RANGE OF SUSTAIN LEVEL: 0 to 100% of contour peak.
WIDTH OF SWEEP OF FILTER BY ITS CONTOUR GENERATOR:
Continuously variable from
0 to 4 octaves.
AUDIO SIGNAL OUTPUTS
HIGH LEVEL OUTPUT: 0.5 volts typical, with 3K ohms nominal
LOW LEVEL OUTPUT: 15 millivolts typical, with IK ohm output
HEADPHONE OUTPUT: 0.3 volts maximum, into standard 8-ohm
FUNCTION: Permanently connected to (a) control
Oscillators 1 and 2, and (b) trigger Contour Generators.
may be switched to control Oscillator 3 and Filter.
DESCRIPTION OF KEYBOARD: Standard 44 key (3-1/2-octave)
. Only lowest key depressed has effect in
controlling Oscillators and Filter. Contour Generators are
activated whenever a single key is depressed.
RATE OF Keyboard
GLIDE: Continuously variable from 1
millisecond to 1 second/octave.
PITCH BENDING RANGE: 5 semitones mini-
MODULATION INJECTION RANGE: 0 to
CONTROL AND POWER CONNECTIONS
EXTERNAL PITCH CONTROL INPUT CHARACTERISTIC: 1 volt change
produces 1 octave frequency change, + 2 percent.
EXTERNAL FILTER CONTROL INPUT: 1 volt change produces 1
octave change in cutoff frequency, + 5 percent.
CONTROL INPUT: Linear control
voltage/gain relationship. Gain range spanned by 0-4 volts.
EXTERNAL TRIGGER INPUT: Switch-closing activates both
AUXILIARY DC POWER SOCKET: +10 volts and -10 volts at 50
DIMENSIONS AND WEIGHT
OVERALL SIZE (with Front Panel down): 28-5/8 inches (72cm)
wide, 17-1/8 inches (41cm) deep, 5-3/4 inches (14cm) high.
NET WEIGHT: 28 pounds (12.7kg).
SHIPPING WEIGHT: 45 pounds (20.5kg).
100-135 and 200-270 volts, 50-60Hz, 40 watts maximum.
major differences in the two boards is that common summing
is used on the new board while individual summing is used on
the old board.
All three oscillators have individual octave switching
signals applied to three adjustable potentiometers providing
precision octave switching of the individual oscillators.
2.2.2 MODULATION MIX Amplifier
A modulation mix Amplifier
selects the output of oscillator
3 or noise, or both, sums and routes them to the amount
control in the left hand Controller
2.2.3 NOISE GENERATOR
The Minimoog contains a noise generator using a transistor
generating white noise in the range of -60dB which is
amplified to produce white, pink or red noise, selected by
the noise Selector
switch. White or pink noise is used for
audio and pink or red for modulation.
2.2.4 HEAD PHONES
is provided to supply sufficient current to
drive standard stereo headphones.
2.2.5 POWER SUPPLY
A dual output Power Supply
with the rectifier on Board 3,
the filter on Board 5 and the transformer on the chassis,
provides + 10 volt regulated power. The input is either 115
or 230 volt as selected through a switch on the top of the
2.2.6 KEYBOARD CIRCUIT
circuit consists of a temperature compensated
current source, the actual Keyboard
and a track and hold
amplifier. The Keyboard
routed to a track and hold Amplifier
where, with no keys
depressed, the circuit is in a hold mode. With a key
depressed, the pitch voltage occurs before the trigger and
the trigger goes off before the pitch voltage is released.
2.2.7 A-440 REFERENCE OSCILLATOR
The A-440 reference oscillator is based on a standard Wein
Bridge oscillator design. The bridge has a phase shift of
zero degrees at approximately 440Hz, supplying a positive
feedback and causing the circuit to oscillate. The frequency
of the oscillation is set by a resistor. Three capacitors
and a resistor limit the signal amplitude to a transistor
collector resulting in a clean sine wave output.
2.2.8 EXTERNAL Amplifier
The external preamplifier is fed to the EXTERNAL INPUT
VOLUME control where the output is fed through a 200 gain
and in turn routed to the EXTERNAL INPUT ON/OFF
switch. This switch allows an external source to be summed
with other signal sources.
2.2.9 OVERLOAD LAMP DRIVER
The output from the 200 gain Amplifier
is also fed to the
overload lamp driver circuit. The amplitude envelope of the
signal is detected and fed to a voltage divider. When the AC
input voltage reaches approximately 1.2 volts, the OVERLOAD
lamp illuminates and is held for a suitable period.
2.2.10 VOLTAGE CONTROLLED FILTER
“Audio” signals are summed and a differential signal current
is generated and applied to a filter ladder. Cutoff
frequency of the filter is controlled by the standing
current through the ladder. The higher the standing current,
the higher the cutoff frequency. A differential signal is
created and fed to a gain Amplifier
which converts the
differential input to a single ended output in tum fed to a
transistor in the voltage control Amplifier
. The FILTER
EMPHASIS control is also connected to the gain Amplifier
providing positive feedback at the cutoff frequency. As the
amount of emphasis is increased, the Q increases and the
filter starts a sine wave oscillation at the cutoff frequency.
The cutoff frequency control current originates in an
exponential voltage to a current Converter
. Control voltages
from the external input, Keyboard
switches, modulation and
the contour generator are summed and fed to the exponential
convertor. A resistor sets the Keyboard
scale at one volt
per octave and in turn the front panel filter CUTOFF
FREQUENCY control is calibrated in a similar manner.
2.2.11 VOLTAGE CONTROLLED Amplifier
The input signal from the voltage controlled filter is AC
coupled to a differentia) transconductance multiplier. The
gain of the transistor is current controlled; the greater
the current, the higher the gain.
2.2.12 CONTOUR GENERATORS
Separate contour generators are provided for both filter and
loudness contours. Each contour generator has its own
controls consisting of ATTACK, DECAY and SUSTAIN. Contour
generators are triggered by an internal voltage trigger from
and/or the rear panel S-TRIG jack. The amount
of contour control adjusts the sweep of the voltage
controlled lowpass filter.