Doepfer

Notes: Module A-118-2 is the slim version of module A-118-1 and offers essentially the same features as the A-118-1. But the distances between the controls are smaller and rubberized small-sized knobs are used. In return the front panel has 4 HP only which is half the width of the A-118-1. The module is primarily planned for applications where only limited space is available. The functional difference between A-118-1 and A-118-2 is the additional T&H/S&H unit which is not included in the A-118-1.

The module generates the signals white noise, colored noise, continuous random voltage and stepped random voltage (derived from the continuous random voltage by means of a S&H/T&H unit).

The noise signal is generated 100% analog by amplification of the noise of a transistor. White and colored noise are usually used as audio sources. The random voltages are normally used as control voltages (e.g. for filter frequency or any other voltage controlled parameter).
The A-118-2 gives you the ability to mix the relative amounts of Red (low frequency component) and Blue noise (high frequency component) in the colored noise output.

For the continuous random voltage the rate of change (Rate) and amplitude (Level) of the random voltage can be adjusted. The continuous random voltage is derived from the colored noise signal by low pass filtering. Consequently the settings of the controls for the colored noise (Blue, Red) affect the behavior of the random voltage! A dual color LED (red = positive / yellow = negative output voltage) indicates the continuous random voltage.

The continuous random voltage is used as source for the S&H/T&H unit. The type of operation can be set to S&H (sample and hold) or T&H (track and hold). When T&H is chosen the output signal follows the input signal (= continuous random voltage) as long as the Clock input is "high". As soon as the clock signal changes to "low" the last voltage is stored. When S&H is chosen the input signal (= continuous random voltage) is sampled at the rising edge of the Clock signal.

For the Clock signal a "digital" signal (e.g. Clock, Gate, rectangle output of an LFO) is required. It does not work with slowly changing continuous CV signals. Another dual color LED (red = positive / yellow = negative output voltage) indicates the stepped random voltage.

Controls:

Blue: share of the high frequencies in the the colored noise output
Red: share of the low frequencies in the the colored noise output
Rate: rate of change of the continuous random voltage
Level: amplitude of the continuous random voltage
TH/SH: switches between T&H and S&H

Inputs and outputs:

RND: continuous random voltage output (with LED display)
TH/SH: stepped random voltage output (with LED display)
Clk: Clock input of the S&H/T&H unit
C Noise: colored noise output
W Noise: white noise output

Important notes:

After power on it takes a few minutes until the two noise signals and the random signals are generated. The module is not faulty when after power on the signals do not appear immediately!

The S&H/T&H function is realized by pure analog circuitry (electronic switch followed by a holding capacitor and buffer). Consequently the output voltage drifts a bit in the holding state because the capacitor is discharged by parasitic resistors. The drift depends also upon environmental conditions like humidity or temperature.

Dimensions
4 HP
40 mm deep

Current Draw
20 mA +12V
20 mA -12V

Notes: Module A-149-4 generates four triggered random voltages which meet the criteria choosen by several controls.

Manual controls for the criteria selection:
Octave range (manual control "Oct."): this parameter defines how many octaves are covered by the random voltages (0 ... +5V, with "Oct." control fully CCW only 0V are generated)
Grid (6 illuminated radio buttons): this parameter defines the grid of the random voltages:
Octaves (Oct)
Octaves + Quin (Quint)
Chords (Major or Minor chords)
Scale (Major or Minor scale)
Semitones
continuous (i.e. stepless)
Minor / Major (2 illuminated radio buttons): this parameter defines in case of chords or scales if they are minor or major. For all other grids this parameter has no meaning
Sixth / Seventh (2 illuminated separate buttons): these parameters defines if the sixth or seventh is added. Valid only if Oct, Quint, Chord or Scale is chosen as grid.

The output voltages follow the 1V/octave standard (i.e. 1/12 V voltage differenc per semitone) with exception of the Continuous mode. The voltages in this mode are totally random and do not follow the 1V/oct standard (i.e. not a multiple of 1/12V).
The generation of a new random voltage at the output (CV Out 1...4) is triggered by the rising edge of the signal applied to the corresponding trigger input (Trig. In 1...4). The trigger inputs are normalled top down. The minimum trigger level is +2.5V, the maximum level is +12V.

Applications:
random polyphonic structures (in combination with the polyphonic modules A-111-4, A-105-4, A-132-8, A-141-4 and e.g. A-157 as trigger source and A-173-1/2 for transposition of the polyphonic structures)
any application that requires several random voltages
four digital pseudo noise signals when higher trigger frequencies are used

Width: 4 HP / 20.0 mm
Depth: 50 mm (measured from the rear side of the front panel)
Current: +50A (+12V) / -10mA (-12V)