Four-channel MIDI-CV interface for playing polyphonic patches - 16HP
Notes: Module A-190-5 is a four voice Midi/USB to CV/Gate interface. For each voice a pitch control voltage (CV1, 1V/octave standard to control VCOs), a gate output (to control envelope generators) and two additional control voltages (CV2, CV3) are available. The two additional CV outputs can be controlled by Midi velocity, volume, modulation, pitch bend, after touch or free assignable Midi controllers.
- Four voice monophonic (i.e. to control four monophonic voices by four succeeding Midi channels)
- Four voice polyphonic (i.e. to control four monophonic voices by one Midi channel) with several sub-modes (e.g. rotating/non-rotating)
- Two voice polyphonic (i.e. to control two monophonic voices by one Midi channel)
The basic mode is selected by means of a momentary switch (probably Mode or Algor.) and is shown in the LC display. Certain parameters of each mode can be edited (e.g. the midi channel(s), the midi reference note for 0V CV, assigned controllers for CV2 and CV3). For this the momentary switch Edit/Play is used. The parameter values (e.g. midi channels) are shown in the display and can be modified by means of the momentary switches 1...4. In Play mode the LEDs of these four switches display the gate states.
Sound source deriving four subharmonics from an incoming square wave signal - 26HP
Notes: Module A-113 is a new sound source that derives four so-called subharmonics (German: Subharmonische) from an incoming pulse signal. The term subharmonics was introduced by Oskar Sala in connection with his so-called Mixtur-Trautonium. A subharmonic means in this context a sawtooth wave (German: Kippschwinger) whose frequency is derived from a master frequency and the master frequency is an integer multiple in the range of 1...24 of the subharmonic - in other words: the master frequency is divided by an integer 1...24 to obtain the subharmonic.
The output waveform of a subharmonic is sawtooth (as also used in the original Trautonium) and not sine. The term subharmonics is somewhat misleading. The master frequency comes e.g. from an A-110 or A-111 to the frequency input of the A-113. The frequency dividers of the 4 subharmonics is adjusted with up/down buttons as displayed with two character LED displays. The subharmonics are available as single outputs and as mix output with adjustable levels for the subharmonics.
Two gate type control inputs enable to select between 4 different mixtures, i.e. 4 different settings of the frequency dividers. In the original Trautonium these are controlled by foot switches to switch between 3 mixtures while playing (the original Trautonium has only 3 mixtures available but with the 2 gate inputs of the A-113 four different settings can be addressed).
Additionally, the A-113 features a mixture memory with 50 presets. Each preset consists of 4 mixtures that can be selected with the gate inputs, each mixture contains the values of the 4 frequency dividers.
Four voltage controlled LFO's/ VCO's with triangle & rectangle outputs in one single module - 22HP
Notes: Module A-143-4 is a fourfold voltage controlled low frequency oscillator (LFO). As the frequency range includes moderate audio frequencies it can be used as a four-fold VCO too.
- Four independent VCLFOs/VCOs with triangle core
- Frequency range switches: low (bottom position) = LFO mode, high (top position) = VCO mode
- Two frequency control CV inputs for each unit
- CV1 without attenuator (~ 1V/oct)
- CV2 with attenuator
- Manual frequency control
- Internal jumpers for the frequency range of the manual frequency controls:
- Jumper not installed: ~ +/- 1 octave range (mainly for VCO applications)
- Jumper installed: ~ +/- 5 octaves range (mainly for VCLFO applications)
- Sync inputs: Combined Reset/Direction inputs for unit #1 - #3 / Separate Reset and Direction inputs for unit #4 (normalled sockets, i.e. Reset is connected to Direction if the Direction socket is unused) / Up/both/down direction switch for unit #4, for technical details concerning the Reset and Direction function please refer to the sketch below
- Triangle and rectangle outputs for each unit
- Typ. output voltage range -5V ... +5V for both outputs (i.e. about 10 Vpp, symmetrical with reference to 0 V)
- Red/yellow LED displays for the triangle outputs (red = negative output voltage, yellow = positive output voltage)
- Common control section with two CV inputs and manual control (these inputs and controls affect the frequency of all four units)
- Sum outputs for triangle and rectangle with red/yellow LED displays
- Optional ultra-low frequency mode: for this a negative voltage can be applied via a jumper internally to the CV2 input of each unit and the common section (i.e. a negative voltage is normalled to the socket CV2 in question). Then the CV2 - - Attenuator control works as a negative frequency control (i.e. turning up this control lowers the frequency). Herewith LFO periods up to about one hour (or even more) are possible.
- Optional CV bus access via jumper (i.e. the module can pick up the CV from the A-100 bus, e.g. generated by a Midi/CV or USB/CV interface A-190-x or a bus access module A-185-1/2), if the jumper is installed the bus CV affects all four units as the bus CV is added to the CV generated by the common control section
- Typ. frequency range: < 0.001 Hz (~ one hour, LFO mode with ultra-low option) ... 15 kHz (VCO mode with installed frequency range jumpers for the manual frequency controls)
- Heat-up time: ~ 15 minutes (required to heat-up the main circuit by the affixed oven)
The module was planned mainly as a quad VCLFO. But we added a range switch (nothing but a switch for two different capacitors) so that even audio frequencies are possible and the module can be used as VCO with some restrictions too. Because of the closeness of the main circuitry (i.e. four VCO cores within less ~ 1 square millimetre) the oscillators may lock if the frequencies are very close to each other and the VCO frequencies interact marginally. If a high quality quad VCO is required the A-111-4 is recommended as this module has four separate VCO circuits available.
The reset circuitry is optimized for the LFO mode. As it takes some time to discharge the oscillator capacitor the discharge time had to be chosen so that the capacitor is fully discharged in LFO mode. In the high range (where a much smaller capacitor is used) this will cause a zero state duration in the 0.3 ms range if the oscillator is synced (during this time the capacitor is shortened for discharge).
The control scale of the inputs "CV1" is about 1V/octave. To improve the behaviour in the VCO mode a tempco circuit is used to keep the temperature of the exponential converter at a fixed temperature (similar to the tempco option of the DIY SYNTH). That way the frequency of the VCOs (and even the VCLFOs) is nearly independent from the environment temperature. But the accuracy (1V/octave scale and temperature compensation) is not as precise as for the dedicated VCOs A-110 and A-111-1.
Complex 12-stage phase shifter with separate in- and outputs for all phaser stages
Notes: Module A-101-3 is a 12-stage phase shifter with vactrols as phase shifting elements. Vactrols are known for their smooth sound behaviour. In contrast to other phaser designs, the A-101-3 is much more flexible and offering a lot of new features not available from other phasers on the market. The main difference is that the Doepfer design offers access to each of the 12 input and output stages leading to a lot of new filters that cannot be obtained in other ways. Especially the free patchable feedback loops (yes, not only one feedback loop is possible) between each of the 12 stages, the separate phase shift control for the stages 1-6 and 7-12, and the 2 polarizers intended to control the feedback loops lead to completely new filter types (a polarizer is a circuit that is able to generate positive and negative amplifications in the range -1...0...+1 with -1 = inversion, 0 = full attenuation, +1 = unchanged signal, for details concerning the polarizer function please look at the A-133 VC Polarizer or A-138c Polarizing Mixer module).
Internally, the module is made of 2 independent 6 stage phase shifters (1-6 reps. 7-12) with separate audio inputs (with attenuators), audio outputs (with mix control), and phase shift control units. The phase shift control units feature both manual and voltage-controlled phase shifting (e.g. from a LFO, ADSR, Random Voltage, Theremin CV, Foot Controller CV ...). For each sub-module a phase shift display (LED) is available. The LED shows the illumination state of the 6 vactrols of the sub-module in question as it is connected in series with the internal vactrol LEDs.
Each of the 12 phase shift states is equipped with an audio output socket and feedback input socket to obtain full flexibility to create a multitude of different filters. The audio input signal and the output signals of stage 6 resp. stage 12 are mixed with 2 manual controls to obtain effects at two audio outputs (for normal phase shifting effect this is 50% input signal and 50% phase shifted signal). The two submodules are internally connected via normalized sockets so that two 6 stage phase shifters can be obtained without external patches. Audio output of stage 6 is normalized to audio input of stage 7 and CV input 1-6 is normalized to CV input 7-12. But due to the open structure of the module even other stages than stage 6 and stage 12 can be used as outputs to generate different sounds (simply patch the desired stage output to the normalized mix input socket).
Notes: Module A-187-1 is a DSP based effects module. Four parameters of the selected digital effect are voltage controlled. The main effect (e.g. reverb, delay, pitch-shifter, equalizer) is selected by the two small buttons effect up/down. The upper row of the display shows the effect that is currently selected. In the lower row the four parameters are shown as well as a small bar left from the abbreviation that displays the current parameter value. Each parameter can be adjusted manually (upper potentiometer row) and modified by external control voltages (lower row of the potentiometers and upper row of the sockets). The lower row of the sockets contains the two audio inputs and outputs.
Another button (bypass) is used to turn the effect on/off. When bypass is chosen the upper line of the display shows in turn "BYPASS" and the name of the pre-selected effect. In the bypass mode another effect can be pre-selected and called-up by pressing the bypass button again. Even the effect parameters can be adjusted and are displayed with the bar graphs. But they become effective not before the bypass mode is left.
The module is equipped with two audio inputs and two audio outputs because the DSP board features stereo audio processing. The audio inputs can process usual A-100 signal levels without clipping/distortion. For higher levels external attenuators (e.g. A-183-1) or VCAs may be used.
A ready-made DSP board is used inside the A-187-1 module. Consequently, only these effects and parameters are available that are supported by the DSP module. Some parameters can be changed only in steps or with audible artefacts. The DSP board has 20 Bit DA and AD converter with 32 kHz sample rate available. The inter sound processing uses 24 Bit.