Precision adder (mixer) and buffer for control voltages - 6HP
Notes: Module A-185-2 is a precision control voltage adder/buffer. Precision means that the amplification of the inputs without attenuators is exactly 1.00 and is suitable to add control voltages for the pitch control of VCOs (e.g. from keyboard + sequencer 1 + sequencer 2). Summing resistors matched to 0.1% are used to obtain an accuracy of 0.1% for the added voltages.
The module is equipped with four CV inputs: one with attenuator and three without attenuator. Each input is normalled to +1 V (i.e. if no plug is inserted the input contributes 1 V to the sum appearing at the output).
The input with attenuator can be used for common modulations (e.g. from an LFO, ADSR, Theremin, Pitch-Bender) for all VCOs connected to the output. The Lev.1 control is used to adjust the depth of the modulation, the first switch selects the polarity of the modulation. If no signal is connected to the first socket the attenuator works as a (fine) tuning knob because a voltage in the range 0...+1V (right position of the switch) or 0...-1V (left position of the switch) is added to the CV output.
The inputs without attenuators are planned to add control voltages coming out of keyboards, sequencers, Midi-to-CV interfaces, ribbon controllers or other CV sources that follow the 1V/oct standard. For example the CV of a keyboard can be used to transpose the CV coming from a sequencer, or the CV of a slow sequencer can be used to transpose the CV from a fast sequencer.
Each input is equipped with a three-position switch that determines if the corresponding voltage is added (right position), subtracted (left position) or if the input has no effect (centre position). If no plug is inserted the corresponding switch works as an octave switch for the lower three sections as the default 1 V are added or subtracted to the output voltage according to the switch position. The first switch can be used to add a variable voltage to the sum output. The variable voltage is adjusted with the Lev.1 control and the knob works then as kind of a (fine) tuning control.
The module is equipped with 4 outputs: three non-inverting and one inverting ouput. An internal jumper can be used to connect the non-inverted or inverted output to the CV line of the A-100 bus. That way the module can used to control several VCOs that are connected to the same bus board as the A-185-2 (same functionality as A-185-1).
Notes: Module A-151 (Quad Sequential Switch) is like an electronic four-position rotary switch.
It includes trigger and reset inputs, four in/outputs, and a common out/input. Each time a pulse is received at the trigger input socket, the common out/input is connected to the next in/output. After the fourth in/output, the next trigger makes it step back to the first again, and so on. A positive pulse at the reset input switches the out/input immediately back to the first in/output. Voltages in the range -8V...+8V at the O/I resp. I/O sockets can be processed by the module.
Four LED's indicate the active in/output (ie. the one that is connected to the out/input at any particular time).
Dual quantizer for CV's, converting a continuous positive input voltage into a stepped output voltage - 8HP
Notes: Module A-156 is a Dual Control Voltage Quantizer. A quantizer converts a continuous control voltage in the range 0...+10V into a stepped output voltage in the same voltage range (i.e. only certain voltages occur). Normally 1/12 V steps are used to obtain semitone steps. Quantizer 2 of the A-156 allows has more sophisticated quantizing modes like major scale (i.e. only voltages corresponding to the major scale), minor scale, major chord, minor chord, fundamental + fifth and addition of seventh or sixth when chords are selected. Only those voltages appear at the CV output which comply with the selection rule (e.g. minor chord with seventh). The mode setting of quantizer 2 is done with 3 switches (1-0-1 type with middle position). From the factory quantizer 1 is working in the semitone mode. But there is a jumper on the pc board that can be changed so that even quantizer 1 uses the same scale as quantizer 2.
For each quantizer the following in/outputs are available:
- Control voltage input (CV In): The input for the continuous voltage to be quantized
- Control voltage output (CV Out): The output of the quantized voltage
- Trigger input (Trig.In): If this jack is left open the quantizer is working permanently. If a rectangle voltage is applied quantisation happens only at the rising edge of the signal (e.g. from an LFO or MIDI-to-Sync interface). Thus the quantizing can be synchronized with other events
- Trigger output (Trig.Out): Whenever a quantisation happens (i.e. a new voltage is generated at the CV Out) a positive pulse occurs at this output. It may be used to trigger an envelope generator (ADSR) or for triggering other modules (sequential switch A-151, trigger divider/sequencer A-160/161, trigger delay A-162, ...). If none of these functions are used the jack is left open
On top of that the A-156 is provided with a common transpose CV input having an additive effect on both quantizers. This input is quantized in semitone steps. A typical application is the transposition of a sequence generated by the A-155 by a second control voltage (e.g. coming from the MIDI-CV interface A-190).
- Quantizing the CV sequence generated by an A-155 (semitone, only major scale, only minor scale and so on)
- Quantizing the voltage coming from the Trautonium Manual / Ribbon Controller A-198, Theremin A-178 or Light-to-CV module A-179 to get accurate semitones or major/minor scale tones
- Arpeggio-like effects with LFO, random, noise, envelope generators as CV sources (for negative or symmetrical voltages an offset must be added, e.g. with the offset/attenuator module A-129-3, to obtain positive voltages for the A-156 input)
Voltage-controlled clock multiplier with CV or manual control - 4HP
Notes: Module A-160-5 is a voltage controlled clock multiplier. The incoming clock signal (socket Clock In) is multiplied by a factor that depends upon the control voltage on socket CV In (0...+5V) and the position of the Mode switch. The multiplied clock signal is available at the socket Clock Out. According to the position of the Mode switch different clock multiplying factors are assigned to the control voltage. With 0V CV no clock output is generated. This state is indicated by "all LEDs off". With increasing CV integer factors (left position of the mode switch), power of two factors (middle position) or a mix of both (right position) are obtained. Nine LEDs are used to show the currently selected multiplying factor. In addition two LEDs are used to display the incoming and outgoing clock signal.
A manual control is used to adjust the clock multiplication factor manually without the need of an external control voltage. The voltage generated by this control ("Manual") is normalled to the CV In socket. As long as no plug is inserted into the CV In socket the clock multiplication factor is adjusted by means of the manual control knob and displayed by the LEDs. For dynamic applications (like the ratcheting function described below) the manually generated CV is overwritten by the external CV which has to be fed into the CV In socket.
The module can be used for all kind of clock multiplying applications. One important example is the generation of so-called ratcheting sequences. The band Tangerine Dream is famous for this kind of sequences. A normal sequencer generates only one gate signal per step. A ratcheting sequence may have also more than one gate pulses per step. This function can be obtained by using the A-160-5: one CV output of the sequencer is used to define the number of gate pulses per step. If the control of the step in question is fully CCW the generated CV is 0V and no gate signal is generated (mute of the step). When the control of the step in question is turned clockwise one, two or more gate pulses are generated depending upon the position of the mode switch and the voltage generated by the CV at this step.
Technical note: Due to the nature of clock multiplying it takes a few input clock pulses until the clock output is stable. One has to average a few input clock pulses to generate the multiplied clock output signal. Even when the input clock frequency changes it will take a few cycles until the output clock signal is correct as the module cannot foresee the future of the clock input signal. The generated clock output signal is derived from the last few cycles of the clock input signal. Consequently the module should be driven only by a clock signal with constant or slowly changing frequency.
Notes: Module A-151 (Quad Sequential Switch) is like an electronic four-position rotary switch.
It includes trigger and reset inputs, four in / outputs, and a common out / input. Each time a pulse is received at the trigger input socket, the common out / input is connected to the next in / output. After the fourth in / output, the next trigger makes it step back to the first again, and so on. A positive pulse at the reset input switches the out / input immediately back to the first in / output (see Fig. 1). Voltages in the range -8V...+8V at the O/I resp. I/O sockets can be processed by the module.
Four LEDs indicate the active in / output (i.e. the on that is connected to the out / input at any particular time).
Notes: A-180-9 is another simple but useful tool. It can be used to connect up to 14 signals between different cases by means of standard network cables (RJ45). These cables are available all over world smoothly in different lengths and colours. From the factory two black network cables with 0.5 m length are enclosed.
The upper network connector is wired to the eight sockets 1-8, the lower to the six sockets A-F. That way it's possible to pre-patch different cases and connect signals, that are required in all cases (e.g. clock, start/stop, master CV) by means of one or two cables only instead of 14 individual patch cables. When only eight signals are required only the upper network connector is required and the sockets 1-8 are used. When more than eight signals have to be patched both network connectors have to be used. It's also possible to wire the upper and lower network to different cases (i.e. signals 1-8 to external case #1 and signals A-F to external case#2).
The module is fully passive (no power supply required) and simply wires the 14 sockets to 14 pins of the network connectors.
The A-180-9 comes in pairs for combining two modular systems.
Notes: Module A-138n is a simple four channel mixer, which can be used with either control voltages or audio signals. Each of the four inputs has an attenuator available. The output is twice available (two sockets, hard-wired like a multiple).
The module is the slim version of module A-138a and offers nearly the same features. 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-138a. The module is primarily planned for applications where only limited space is available. The only functional difference compared to the A-138a is the missing attenuator for the (dual) output.
Notes: Module A-182-1 is a simple passive multi-connector similar to the multiples modules A-180-1/A-180-2. In contrast to modules A-180-1/2 each socket is equipped with a 3-position switch that allows to connect the corresponding socket to the internal bus #1 (left position), bus #2 (right position) or to turn the socket off (centre position).
- All switches in left position or all switches in right position: 8-fold multiple
- Four switches in left position and four switches in right position: two 4-fold multiple
- X switches in left position, Y switches in right position and Z switches in centre position: two separate multiples with some sockets turned off
Frequency divider for clock, trigger & gate signals - 4HP
Notes: Module A-160 is a frequency divider for clock/trigger/gate signals, designed to be a source of lower frequencies, particularly for rhythm uses. The Trigger input will take clock signals from, e.g. an LFO, MIDI sync, or the gate from a MIDI-CV interface.
At the outputs, you have access to the sub-divided clock signals, from half the clock frequency down to 1/64. The low/high levels of the output signals are 0V and about +10V.
The A-160 also has a reset input. Whenever a reset signal is sensed, all outputs are set to zero, until the reset voltage disappears.
The Clock Divider can be used in combination with the A-161 Clock Sequencer to produce stepped sequences with a length of from one to eight events.
Notes: A-138s is a simple but useful 4-in-2 mixing tool. It has four inputs available. Each input is equipped with an attenuator (Level) and a panning control that is used to distribute the signal to the left and right output. Beyond stereo mixing it is equally suited to create variable parallel routings. For example: Any of the four inputs may be routed in variable intensity to feed two filters.
You may regard the A-138s as a smaller version of the A-138m Matrix Mixer.
Inputs and outputs are DC coupled, i.e. the module can be used for the mixing of control signals too.
- 3U Eurorack module, 8 HP wide, 30 mm in depth
- Power consumption: 10 mA at +12 V and 10 mA at -12 V
Notes: Module A-130-2 is the slim version of module A-132-3 and offers essentially the same features. 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-132-3. The module is primarily planned for applications where only limited space is available.
The module is composed of two identical voltage controlled amplifiers (VCA). Each VCA has a manual gain control (also named Initial Gain) and a control voltage input with attenuator. The character of the control scale can be switched to linear or exponential. All inputs and outputs are DC coupled. Consequently the VCAs can be used to process both audio and control voltages (e.g. for voltage control of the level of LFO or envelope signals). The signal input has no attenuator available but is capable to process up to 16Vpp signals (i.e. -8V...+8V) without distortion. For the processing of higher levels an external attenuator (e.g. A-183-1) is recommended.
The amplification range is 0...1. Even with a higher external control voltage the amplification remains at 1 (kind of "amplification clipping" at 1).
Controls (for each of both units):
- Gain: manual gain control (Initial Gain) in the range 0...1
- CV: attenuator for the CV input
- Lin/Exp: switches the VCA characteristic to linear or exponential, in center position the VCA is off (mute function)
Inputs and outputs (for each of both units):
- CV: control voltage input, min. +5V required for max. amplification (1) with CV control fully CW and Gain fully CCW
- In: signal input, max. 16Vpp (+8V...-8V) without distortion
- Out: signal output
Notes: Module A-196 contains a so-called phase locked loop (PLL). The basic PLL system is shown in the sketch at the bottom of this page. A PLL consists of three parts: voltage-controlled oscillator (VCO), phase comparator (PC), and low-pass filter (LPF). All parts are normally connected to form a closed-loop frequency-feedback system.
This is how a PLL works: The output of the internal VCO (linear CV control, rectangle output) is compared with an external signal (e.g. the rectangle output of a A-110 VCO) in the so-called phase comparator (PC). The output of the phase comparator is a digital signal (low/high/tristate) that indicates if the frequency resp. phase difference of the two input signals is negative, zero or positive. The output of the phase comparator is processed by a low pass filter (LPF) to generate a smooth voltage that is used to control the frequency of the internal VCO. The 3 units VCO, PC and LPF form a feedback loop that works like this: The control voltage (output of the LPF) increases as long as the external frequency is higher than the frequency of the internal VCO und stops increasing when both frequencies become identical. The control voltage decreases as long as the external frequency is lower than the frequency of the internal VCO und stops decreasing when both frequencies become identical.
But there are some stumbling blocks: Different types of phase comparators with advantages and disadvantages can be made. Some phase comparators e.g. even lock at harmonics, i.e. if the two frequencies to be compared are integer multiples. But for some applications this can be used to create interesting effects. The A-196 contains 3 different types of phase comparators: PC1 is a simple exclusive OR, that even locks at harmonics. PC2 is a so-called RS flipflop and PC3 a more complex digital memory network. The user can select one of the three phase comparators with a 3-position switch. When PC2 is used a LED displays the "locked" state, i.e. when the frequency of the internal VCO is identical to the external frequency.
Special attention has to be directed to the frequency of the LPF. To obtain a smooth control voltage for the VCO the frequency of the LPF has to be much smaller than the lowest frequency of the internal or external audio signal. Otherwise the frequency of the internal VCO will jitter or wobble around the correct frequency. But for special effects this frequency jitter can be used intentionally. Example: frequencies in the range 50Hz...1kHz have to be processed with the PLL. Therefore the frequency of the LPF has to be about 10Hz or even less. Such a low frequency of the LPF causes a noticeable slew of the internal VCO. When the frequency of the external signal jumps e.g. between 500Hz and 1kHz it takes about 0.1 second until the internal VCO reaches the new frequency (like portamento). So one has to find a compromise between frequency jitter and portamento. But these remarks are valid only for the "ideal" working PLL. As the A-196 is used in a musical environment the "problems" and disadvantages with jitter and slew time lead to additional musical applications like portamento effects, wobbling frequencies or harmonic locking according to the type of frequency comparator and time constant of the PLL low pass filter. Instead of the internal manually controlled low pass filter the voltage controlled slew limiter A-171 can be used to obtain voltage control of this parameter. Normal audio filters (e.g. A-120, A-121) cannot be used for this job as the minimum frequency is to high (down to a few Hz or even less necessary) and the signal has to be DC coupled due to the low frequencies. Audio filters are normally AC coupled.
Another very important application of a PLL is frequency multiplication in combination with an external frequency divider. For this the output of the PLL-VCO is processed through an external frequency divider (e.g. A-163, A-160, A-161, A-115) before it is fed to In1 of the phase comparator. In this case the frequency of the PLL-VCO will be a multiple of the master frequency. E.g. if the A-163 is used and adjusted to dividing factor 5 the frequency of the PLL-VCO will be 5 times the frequency of the master VCO. Consequently, frequency division (A-163) leads to frequency multiplication with the PLL circuit. In combination with the PLL low pass frequency several effects can be realized (frequency multiplication with portamento or wobbling). The frequency multiplication can even be used to drive a graphic VCO. If your graphic VCO e.g. has 8 steps (e.g. A-155) and you use a frequency divider with factor 8 in the PLL feedback the output of the graphic VCO has the same frequency as the master VCO. Another application is the generation of pseudo-harmonics (not real harmonics as only rectangle waves are available) or clock generation for switched-capacitor filters.
Notes: 2HP narrow version of the A-180 multiples module. It is a passive signal splitter suitable for audio or CVs. Two sets of four jacks are interconnected, by placing a solder bridge you can connect all eight jacks.
Envelope follower & pre-amplifier for microphone/line-signals - 8HP
Notes: Module A-119 (External Input / Envelope Follower) is designed to allow external audio signals to be integrated into the System A-100. It comprises a pre-amp, envelope follower, and comparator.
The pre-amp has two inputs: an unbalanced input for line level signals, with a gain factor of from 0 to 20, and a balanced input with a gain factor of from 0 to 500, for insertion of low level signals, for instance from a microphone or electric guitar.
The Envelope Follower reads the signal level of the input, and puts out a proportional voltage as an envelope at its own output.
The comparator generates a gate signal whenever the input goes above an adjustable trigger threshold.
Three LED's help you keep track of overload, the envelope, and the gate signal.
VCO module featuring four precision oscillators - 18HP
Notes: A-111-4 contains four precision VCOs and has individual controls, inputs and outputs for each VCO available as well as a common control and output unit. After all the A-111-4 is very similar to four A-111-3 without LFO mode but built in output mixers for the three waveforms, and a master unit for all four VCOs.
Controls, inputs and outputs for each of the four VCOs:
- 1V/Octave CV input
- Octave switch (+1 / 0 / -1 octave)
- Tune control (range internally adjustable by jumpers: ~ 2 semitones / ~ 1 octave / ~ 4 octaves)
- Modulation CV input
- Modulation destination:
- Upper position: exponential frequency modulation (XM)lower position: linear frequency modulation (LM) or pulsewidth modulation of the rectangle (PM), selectable via internal jumper
- Frequency Modulation (FM) or Pulsewidth Modulation of the rectangle (PWM)
- Modulation intensity
- Triangle output
- Sawtooth output
- Rectangle output (about 50% without external PWM)
- Sync input (hard or soft sync internally selectable via jumper, CEM3340 hard sync type)
- Min. 10 octaves range (with appropriate external CV)
- CEM3340 based VCO (triangle core)
- Each VCO has it's own separate internal +/- power supply for each for best stability and the prevention of unwanted synchronisation of the VCOs
Controls, inputs and outputs of the master section:
- 1V/Octave CV input
- Octave switch (+1 / 0 / -1 octave)
- Tune control (range internally adjustable by jumpers: 2 semitones / 1 octave / 4 octaves)
- Frequency Modulation CV input (FM)
- FM intensity
- Triangle sum output
- Sawtooth sum output
- Rectangle sum output
- As soon as the single waveform output of a VCO is patched this waveform of the VCO in question is removed from the sum (this function can be turned off for each single output socket by means of solder bridges on the pc board, i.e. the sum contains then all signals independent of the patching of the single output)
- CV output (outputs the sum CV that is used to control all four VCOs)
- Bus CV (selectable via jumper)
- Fat sounding monophonic VCO with the possibility to adjust any intervals
- Paraphonic patches in combination with the polyphonic CV interface A-190-5 (all four VCOs processed by one VCF/VCA)
- Full polyphonic patches in combination with the polyphonic CV interface A-190-5 and four complete VCF/VCA sections
- Complex VCO patches with up to four VCOs by means of the frequency modulation features (exponential an linear) and the sync functions
Notes: Module A-145-4 is a simple quad LFO (Low Frequency Oscillator). Not a very "exciting" module, just a bread-and-butter device and a simple demon for work. Virtually in every modular system several LFOs are required for modulation purposes. The module contains four simple LFOs with the waveforms triangle and rectangle. A dual colour LED (red = positive / yellow = negative output voltage) indicates the triangle output of each LFO. The frequency range can be chosen for each LFO individually by means of a jumper between about 50 Hz ... 0.04 Hz (about 20 seconds, jumper removed) and about 2Hz ... 0.002 (about 8 minutes, jumper installed).
The module can be treated as a slimmed version of the quad LFO A-143-3 as it has similar features available. 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 less than one third of the A-143-3. The module is primarily planned for applications where only limited space is available. The functional difference compared to the A-143-3 are the missing sawtooth outputs and frequency range switches.
Notes: A-182-2 is a simple passive module that contains four changeover switches, which are used to connect or disconnect the sockets of the corresponding socket triplet:
- In the upper position of the switch the upper socket of the corresponding socket triplet is connected to the centre socket
- In the lower position of the switch the lower socket of the corresponding socket triplet is connected to the centre socket
- In the centre position of the switch the sockets are not connected
Each unit of the module can be used to switch between two signals or to interrupt/connect a signal. In the last case the third socket of the triplet is not used.
The module is fully passive and both audio or control signals can be switched.
Notes: A-135-2 is a miniature version of the A-135-1. Behind a front panel with 8 HP only four linear VCAs (voltage controlled amplifiers) and a voltage controlled mixer based on the VCAs are available.
Controls, In/Outputs and Functions of each VCA:
- Level (manual control of the VCA amplification), small rubberized knob (L1...L4)
- Control voltage input with associated attenuator (CV1...CV4), for the full VCA control range about 0...+5V control voltage are required (attenuator fully clockwise), for higher control voltages the attenuator is used, the attenuators are without knobs, just plastic shafts with white marker
- Signal Input
- Signal Output
- All inputs and outputs are DC coupled. Consequently the VCAs can be used to process both audio and control voltages (e.g. to control the level of LFOs or envelopes)
- The signal input is not equipped with an attenuator. But the VCAs can process all signals up to 15Vpp / -7.5...+7.5V without clipping. In case of higher levels an external attenuator is required (e.g. A-183-1).
- The available amplification range is 0...1, the maximal amplification is 1 (i.e. it "clips" and remains at 1 even if the control voltage goes beyond the value that corresponds to amplification 1)
Functions of the voltage controlled mixers:
- Two outputs ("Selected" and "All")
- Selected output: the ouput if a VCA is removed from this sum signal when a plug is inserted into the corresponding VCA output.
- All output: sum of all VCA outputs, regardless of inserted plugs into the VCA outputs
- The maximal amplification is about 0.6 to avoid clipping at the mixer outputs (otherwise the outputs may distort with 15Vpp signals at each signal input and full amplifications)
Special functions of the voltage controlled mixers (selectable by internal jumpers):
- Dual Stereo VCA: In this case the control unit of VCA1 (L1 + CV1) affects also VCA3 and the control unit of VCA2 (L2 + CV2) affects also VCA4, the control units of VCA2 and VCA4 are out of operation
- Quad VCA: In this case the control unit of VCA1 (L1 + CV1) affects all four VCAs. The control units of VCA2, VCA3 and VCA4 are out of operation. In this mode the module has the same function as module A-132-2. That's why module A-132-2 will be discontinued.
- Normalling of the signal inputs: by means of internal jumpers signal input 1 can be normalled to signal input 2, signal input 2 to signal input 3 and signal input 3 to signal input In 4. That way the same input signal can be distributed to four different channels by means of control voltages (e.g. quadrophonic distribution of audio signals). Suitable control voltage sources are e.g. A-144 (Morphing Controller) or A-143-9 (Quadrature LFO).
12HP random voltage generator for Eurorack, with 4 CV outputs
Notes: Module A-149-1 is the first module of the A-149-x range. In this group we present by popular request several functions of Don Buchla's "Source of Uncertainty 265/266" (SOU) modules that cannot be realized with existing A-100 modules. Many functions of Buchla's 265 and 266 SOU can be realized with existing A-100 modules. For details please refer to A-100 patch examples.
Module A-149-1 has available four different analogue random control voltages that are generated in different ways.
The "Quantized Random Voltages" section has available 2 CV outputs: "N+1 states" and "2N states". N is an integer number in the range 1...6 that can be adjusted with the manual control (Man N) and an external control voltage CVN with attenuator. Whenever the rising edge of the input clock signal (Clk In) appears a new random voltage is generated at the N+1 resp. 2N output. The N+1 output is capable to generate N+1 different voltage levels (or states), the 2N output up to 2N different states. If for example N is set to 4 the N+1 output generates up to 5, the 2N output 16 different states. The voltage steps of the 2N output are adjusted to 1/12 V in the factory. Consequently, exact semitones can be obtained in combination with a VCO. The voltage steps of the n+1 output are adjusted to 1.0 V in the factory corresponding to octave intervals in combination with a VCO. For each output a trimming potentiometer is available on the pc board that enables the user to select other voltage steps for the output in question.
Even the "Stored Random Voltages" section has 2 stepped CV outputs available: one with even voltage distribution of the max. 256 output states and second one with adjustable voltage distribution probability. The distribution probability is adjusted by a manual control (Man D) and an external control voltage CVD with attenuator. With the control set fully counter-clockwise most of the random voltages will be low magnitude but even medium and high magnitude voltages may appear but with smaller probability. As the control is turned to the right (or a positive control voltage appears at the CVD input) the distribution moves through medium to high magnitude voltage probability. The symbol at the lower jack socket shows this coherence graphically. The voltage range is 0...+5V for both outputs of the "Stored Random Voltages" section. For each output a trimming potentiometer is available on the pc board that enables the user to select another voltage range for the output in question.
The A-149-1 can be extended by 8 random digital voltages with the A-149-2 Digital Random Voltages module.
Notes: A-149-2 is an extension module for A-149-1. It makes available 8 digital random voltages (i.e. only low/high states like a gate signal). The outputs are controlled by the "Quantized Random Voltages" section of the assigned A-149-1 and correspond to the 8 digital outputs of the shift register that is used to generate the Quantized Random Voltages. As the alteration of the A-149-2 outputs is clock controlled by the Clk In of the "Quantized Random Voltages" section of the A-149-1 the A-149-2 can be used to create random rhythmical sequences.
The A-149-2 requires the A-149-1 and has to be mounted directly to the left or right of the A-149-1 as an internal ribbon cable connection has to be established between A-149-1 and A-149-2.
Reverb effects module with spring reverb tank - 8HP
Notes: Module A-199 is a spring reverb module. The reverb effect is electronically simulated by means of 3 spiral springs. Spring reverb systems have a very characteristic sound that is based on the (insufficient) mechanical properties of the springs like signal delays, audio resonances, limited frequency range, acoustic feedback behaviour, sensitivity to mechanical shocks and others.
The 3-spring system used in the A-199 ensures a "dense" reverb because of the different properties of the three springs.
The A-199 implies some special features that are not self-evident for spring reverb units:
The reverb signal can be fed back to the input using the Feedback control. Even self-oscillation of the springs similar to the self-oscillation of filters is available. The feedback loop can lead even via external modules like VCA, VCF, phaser, frequency shifter, vocoder, distortion/waveshaper, ring modulator and others. In this case the reverb output of the A-199 is connected to the input of the external module(s) and the output of the external module(s) is fed back to the Ext. Feedback In socket of the A-199. This socket contains a switch that interrupts the internal feedback loop as soon as a plug is inserted.
Another feature is the Emphasis control. This enables the adjustment of the accentuation of middle frequencies (around ~ 2kHz).
With the Mix control the relation between original and reverb signal appearing at the mix output is adjusted.
Using all these features very extreme and unusual effects can be generated with the A-199.
Notes: Theremin module for generating a variable control voltage by approaching/removing hand to/from an antenna. The distance range is about 30-40 cm. Additionally the module is equipped with a Gate output with adjustable threshold level. Controls/Inputs/Outputs: antenna input, offset (knob for zero adjust), 2 x CV out, 2 x LED (for CV control positive/negative and zero offset adjust).
To simulate the original Theremin two A-178, a VCO (e.g. A-110) and a linear VCA (e.g. A-130 or A-132) are required. But of course the A-178 can be used to control other functions in the A-100 (e.g. filter frequency, modulation depth and/or speed, tempo, attack/decay time and so on).
The CV output voltage of the A-178 can range - according to the setting of the front panel controls - from -10V...+10V. The gate output switches from 0V to about +10V.
- Controlling any voltage controlled parameter of the A-100, e.g. pitch or pulsewidth (VCO A-110), loudness (VCA A-130/131/132), panorama (A-134), filter frequency or resonance (A-120/121/122/123), phasing (A-125), frequency shift (A-126), resonance peaks (A-127), envelope parameters (A-141/142), tempo (A-147)
- Triggering of A-100 activities via gate with adjustable threshold, e.g. starting an envelope (A-140/141/142), Start/Stop of a sequence (A-155), any switching function (A-150/151)
- Conversion into MIDI control change messages is possible with the A-192.
If two or more A-178 are used the distance between the modules/antennas should be at least 40-50 cm. Otherwise the antennas may affect each other.
Notes: 2HP narrow version of the A-180 multiples module. It is a passive signal splitter suitable for audio or CVs. Two sets of four jacks are interconnected, by placing a solder bridge you can connect all eight jacks.
Notes: Module A-176 (Control Voltage Source) provides three voltage sources, to use wherever an extra CV is required. The top two voltage sources (CV 1 and CV 2) have controls for coarse and fine control of the voltage output; the third source (CV 3) just has the one control.
The range of the voltages output can be preset, either to 0 to +5 V or to -2.5 V to +2.5 V depending on your likely requirements. There is a jumper on the circuit board for each of the three voltage sources.
A typical use for the module would be to provide fine as well as coarse tuning for an A-110 standard VCO, (which, unlike the A-111, only has one tune control).
In general, this module will be useful whenever you need a manually controllable CV on a module which doesn't itself have a built-in control.
Two sample & hold units in one module for generating stepped random voltages or slicing signals
Notes: Module A-148 (Dual S&H) has two identical sample & hold modules, designed to produce 'staircase' voltages. The signal present at the sample input is sampled at a rate set by the signal at the trigger input, and held at that voltage at the S&H output.
The exact shape of the staircase depends on the sort of waveform at the sample input: NOISE or RANDOM signals produce random patterns; an LFO produces rising or falling staircase patterns.
Two LEDs for each S&H indicate the voltage (positive or negative) of the sampled signal.
Notes: The A-139-2 is a headphone amplifier module with two mono inputs and a stereo headphone output. It can be used for driving small loudspeakers, LED strips, small magnets etc.
- Two-channel headphone amplifier
- Two audio inputs with level controls
- Input 1 is normalled to Input 2
- Common loudness/master level control
- Headphone output (stereo 1/4" jack socket)
- Max. output power ~ 2 W per channel (@ 8 Ohm load)
- DC coupled inputs and outputs (i.e. also useful for other applications like small loudspeakers, lamps, LEDs, magnets, motors - provided that the power is sufficient)
Notes: Module A-140-2 contains two ADSR type envelope generators behind a front panel with 8 HP only.
Each ADSR provides these controls and in/outputs:
- LED (displays the envelope output)
- A: manual Attack control
- D: manual Decay control
- S: manual Sustain control
- R: manual Release control
- Gate Input
- Retrigger Input
- CVT Input with attenuator (CVT = CV Time)
- Envelope Output 1
- Envelope Output 2
The output voltage range for each envelope is 0 - 10V. The time range of Attack/Decay/Release is about 1ms to 30s.
By means of internal jumpers one can select which time parameters are controlled by the CVT input (e.g. D only or D+R or A+D+R) and in which direction (i.e. if an increasing CVT shortens or stretches the time parameter in question).
Socket CVT can be normalled to an internal fixed voltage (i.e. the switching contact is connected to an internal fixed voltage). That way it's possible to change all time parameters simultaneously by means of the CVT control.
Another jumper is used to set output 2 to normal or inverted envelope.
And another jumper is used for the normalling of Gate 2 to Gate 1 (i.e. ADSR#2 is also triggered by Gate 1).
Two more jumpers are used for the optional bus access to the gate signal of the bus for each ADSR. Changing the positions of the mentioned jumpers allows to modify the factory settings.
Notes: Module A-106-5 is a 12dB multimode filter that is based on the filter circuit of the Oberheim SEM module.
The filter is equipped with a band pass output and a combined low/notch/high pass output. For this output a control knob defines the relation between low and high pass signal. If both signals appear at the same level (i.e. middle position of the Mix knob) one obtains a notch filter. Otherwise the low or high pass signal predominates.
The module does not feature self-oscillation in contrast to most of the other filters of the A-100 system.
The module generates a distorted audio signal if the level control is set to about 50% (i.e. centre position) or more with A-100 standard signals like VCOs.
Notes: Module A-138 is a four channel mixer, which can be used with either control voltages or audio signals. Each of the four inputs has an attenuator, and there's a master attenuator, so that the mixer can be used at the end of the audio chain, i.e. it can be used to interface directly with an external mixer, amplifier, etc.
The A-138b has potentiometers with logarithmic response, so is especially suitable for audio signal mixing.
Envelope generator with CV outputs for modulation - 8HP
Notes: Module A-140 is an envelope generator, and, since it puts out control voltages, counts as one of the modulation devices in a modular system. As soon as the gate input receives sufficient voltage, the ADSR generates a variable voltage, changing in time, called an envelope. This varying voltage is output in normal (positive) and inverted form, and can be used, eg. for voltage controlled modulation of a VCO, VCF, or VCA, or for processing other modules' inputs and outputs.
The shape of the envelope is governed by four parameters: Attack, Decay, Sustain and Release.
The envelope is started (triggered) by a gate signal either from the INT.GATE voltage on the system bus, or, if a signal is put into it, from the gate input socket.
The envelope can also be re-triggered, i.e. start from scratch again, each time a trigger signal is sensed at the Retrig. input socket, when the gate is still open.
Module A-140 has available a three-position toggle switch to select one of three time ranges. The envelope duration ranges from about 50us (microseconds) up to several minutes.
In combination with the Comparator module A-167 a free-running "ADSR-LFO" can be realized.
Reproduction of the legendary British diode lowpass filter - 8HP
Notes: Module A-102 is a reproduction of the legendary low pass filter design that uses diodes in the filter stage as frequency controlling elements - resulting in "strange" resonance behaviour and frequency response, as resonance and frequency are not independent from another.
As for the rest, the A-102 is identical to the A-120 Moog low pass filter, the A-103 (18dB TB303 Filter) i.e. the same controls, inputs and outputs. Only the filter sound is different:
- Manual control of filter frequency
- 3 CV inputs (CV1, CV2, CV3), 2 of them with attenuator (CV2, CV3)
- Input level control
- Resonance control up to self-oscillation (depends upon the frequency setting for the A-102)
18dB low pass filter based on a modified Moog cascade - 8HP
Notes: Module A-103 is a voltage controlled low pass filter with 18dB/octave slope. The circuit is based on a modified transistor ladder (Moog ladder) and is a reproduction of the legendary TB303 filter.
As for the rest the A-103 is identical to the A-120 Moog low pass filter (same controls, inputs/outputs) only the filter sound is different.
Basic voltage-controlled oscillator for the A-100 modular system
Notes: Module A-110-2 is a low-cost voltage-controlled oscillator. It's a slightly reduced version of the standard VCO A-110-1. Compared to the A-110-1, the A-110-2 has no sine output and the (expensive) octave rotary switch is replaced by a 3-position toggle switch. In return, the A-110-2 is equipped with an additional linear FM input and a soft sync input. A jumper is used to select the range of the tune control between about 1/2 octave and about 4 octaves. The width of the module is only 8 HP compared to the 10 HP of the A-110-1.
All other features are essentially the same as for the A-110-1.
Explanation of the jumpers and trimming potentiometers:
- JP2: CV connection to A-100 bus
- JP3: range of Tune control (installed = about 4 octaves, not installed = about 1/2 octave)
- JP4: AC/DC coupling of the linear FM input (installed = DC coupling, not installed = AC coupling)
- P5: 1V/Oct scale
- P6: frequency offset
- P7: high-end trim
- P8: adjustment +1 Oct. range switch
- P9: adjustment -1 Oct. range switch
- P10: temperature VCO heater
The core of the A-110-2 is - like the A-110-1 - a sawtooth oscillator (in contrast to the A-111-1, which is based on a triangle oscillator). The other waveforms are derived from the sawtooth by waveform converters. As the sawtooth reset (i.e. the back-to-zero slope) is not infinitely fast but takes a little bit of time the triangle is not perfect! At the bottom of the waveform it has a small glitch or notch that is caused by the sawtooth reset and cannot be eliminated by the waveform converter. If a perfect triangle is required, the A-111-1 is recommended.
The sawtooth output of the A-110-21 has a falling (or negative) slope. The front panel shows erroneously a rising (or positive) slope. This has no influence on the sound but becomes important when the module is used as an LFO or is mixed with the sawtooth output of another VCO.
The control voltage applied to the socket 1V/Oct is added to the control voltage coming from the bus (interruptible by removing the jumper JP2). Connecting a cable to the socket 1V/Oct does not interrupt the bus CV connection!