MATRIXSYNTH: Doepfer Product Announcements for SUPERBOOTH21

Saturday, September 04, 2021

Doepfer Product Announcements for SUPERBOOTH21

via Doepfer

"Superbooth 2021 is just around the corner. The Superbooth team around Andreas Schneider managed it with their hygiene and safety measures that the event can happen and personal contacts are possible again. The Superbooth takes place from 15 to 18.09.2021 in Berlin. More information is available at the Superbooth Website. We plan to present these new products and would be happy to welcome you at our booth (presumably B047 in the 'Bungalow-Dorf')."

Left: (A-100PB with a keyboard built into the lid, 37 keys, midi interface with 3.5 mm stereo jack socket)

This is the "small brother" of the monster base A-100PMB. It is very similar to the A-100PMB but has only half the width (2 x 84 HP for installation of modules). The suitcase versions A-100P6 or A-100P9 can be positioned on top of the A-100PB because the width of the A-100PB is a bit more than the width of A-100P6/P9 and the footprint of the A-100PB is adapted to the depth of A-100P6/P9. A-100PB is equipped with one power supply (1200mA) and two bus boards. The bus boards are located in the rear area (even those for the modules that are mounted in the front row). This was necessary to take advantage of the full height of the front area for installation of A-100 modules.

Module A-126-2 is a fully analog frequency shifter for audio signals. A frequency shifter is an audio processing unit that shifts each frequency of the incoming audio signal by the same frequency. If the shifting frequency is e.g. 200Hz an incoming audio frequency of 1000 Hz becomes 1200 Hz, 2000Hz becomes 2200 Hz, 3000 Hz becomes 3200 Hz and so on. Pay attention that this is different from pitch shifting where all frequencies are shifted proportional (e.g. 1000>1200Hz, 2000>2400Hz, 3000>3600Hz) ! The frequency range of the internal quadrature VCO is about 8 octaves (about 20Hz ... 5kHz). If required an external quadrature VCO can be used.

The module is equipped with these controls, inputs and outputs:

Frequ. 1: first manual control of the shifting frequency (factory setting: coarse, range about 20Hz - 5 kHz)
Frequ. 2: second manual control of the shifting frequency (factory setting: fine)
by means of internal jumpers the sensitivity of Frequ.1 and 2 can be swapped (i.e. Frequ.1 = fine and Frequ.2 = coarse)
the relation between coarse and fine control is about 25:1 (corresponding to about 8 octaves to 1/3 octave)
FCV In (socket) and FCV (small control without knob): control voltage input with attenuator for the external voltage control of the shifting frequency
Mix: manual control of the up/down shift panning unit, fully CCW = down shift, fully CW = up shift, in between a mixture of down and up
Mix CV In (socket) and Mix CV (small control without knob): control voltage input with attenuator for the mixing unit for external voltage control of the up/down mixing
Audio In (socket), Level (small control without knob) and Overload (LED): audio input with attenuator, typ. audio in level = 1Vpp, the level control has to be adjusted so that the overload LED just begins to light up a bit, when the LED is fully on clipping/distortion occurs, when the LED is permanently off the input level is too low and the signal-to-noise ratio increases
Audio Out (socket): audio output of the frequency shifter
Squelch (small control without knob): controls the squelch function: fully CCW (Env.) the output VCA is controlled by the envelope signal, which is derived from the audio input signal, fully CW (open) the output VCA is permanently open (no squelch function), in between the squelch intensity can be adjusted
Quadrature VCO Outputs (sockets Sin and Cos): outputs of the internal quadrature oscillator, about 12Vpp level (+6V/-6V)
Ext. Inputs Sin and Cos (sockets): required when an external quadrature VCO (e.g. A-143-9 with a wider frequency range or A-110-4 with thru zero feature or A-110-6 with different waveforms) is used instead of the internal quadrature VCO, the levels of the external VCO should be about 10Vpp (8...10Vpp are OK) and the signals have to be symmetrical around zero Volts, the sockets are normalled to the internal quadrature VCO (i.e. the sockets are equipped with switching contacts that interrupt the internal connection as soon as a plug inserted)
VCA ext. CV (socket): used when an external control voltage (e.g. from an envelope generator) should be used to control the output VCA instead of the internal squelch unit, the socket is normalled to the output of the squelch control (i.e. the socket is equipped with a switching contact that interrupts the internal squelch connection as soon as a plug inserted). From about +8V external control voltage the VCA is fully open.
Internal terminals (pin headers, e.g. for a DIY breakout module):
envelope follower output
dome filter output 1
dome filter output 2
ring modulator 1 output
ring modulator 2 output
Up shift output
Down shift output
Technical details:

The analog frequency shifter is based on these trigonometric equivalences:
sin(a)*sin(b) = cos(a-b) - cos(a+b)
cos(a)*cos(b) = cos(a-b) + cos(a+b)
Building the sum and difference of these formulas one obtains:
Sum: sin(a)*sin(b) + cos(a)*cos(b) = 2 cos(a-b)
Difference: sin(a)*sin(b) - cos(a)*cos(b) = -2 cos(a+b)
When (a) in these formulas is treated as an audio signal and (b) as a sine signal it's possible to derive an up or down frequency shift with the frequency amount (b) for the audio signal (a). To realize the formulas these electronic circuits are required:
A phase shifter that shifts all frequencies of the audio signal (a) by 90 degrees (sine and cosine are the same signals but with 90 degrees phase difference). Such a circuit can be realized by means of a so-called Dome filter (named after the inventor Robert Dome). The circuit is made in principle with several allpass filters which have to be dimensioned very carefully so that the phase shift for all relevant frequencies is as close as possible to 90 degrees. In the A-126-2 a 12-stage Dome filter is used which is made with close-tolerance parts (resistors with 0.1% tolerance and capacitors with 1% tolerance). That way the time killing adjustment of many trimming potentiometers (with mutual influence) is avoided.
The Dome filter of the A-126-2 generates 90 degrees phase shift with less than 0.3 degrees error over a frequency range of about 50 Hz to 14 kHz.
A quadrature oscillator (i.e. an oscillator with simultaneous sine and cosine output, similar to the already existing modules A-143-9 or A-110-4
two multipliers: in the A-126-2 two ring modulators are used for this job
a summing unit
a subtracting unit
Beyond that the A-126-2 has some special features:

An envelope follower is used to derive an envelope signal from the audio signal. It generates a voltage that corresponds to the current level of the audio signal. A comparator is used to drive an LED which works as overload display. In addition the envelope signal is used to control a VCA which works as a squelch unit.
The up and down outputs are internally connected to the inputs of a voltage controlled crossfader. That way the relation between up and down signal can be controlled manually and by means of an external control voltage.
The module is fully DC coupled so that even very low frequency shifts are possible (with external quadrature VCO)
The sketch below shows the internal structure of the module in detail and the phase shift of the dome filter.

Module A-138f contains two identical crossfaders with three inputs and one output each. Three different signals are connected to the inputs A, B and C. In the ccw position of the corresponding control only signal A appears at the output. Between ccw and center position a mix of the signals A and B appears at the output. In the center position only signal B appears at the output. Between center and cw position a mix of signals B and C appears at the output. In the cw position only signal C appears at the output.
The module is DC coupled and can be used for both audio and control voltage processing.

Application examples:

Crossfading of VCO waveforms (e.g. saw - rectangle - triangle)
Crossfading of VCF outputs of multimode filters (e.g. lowpass - notch - highpass - bandpass)
Crossfading of control voltage signals (e.g. envelope - LFO - random)

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)
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 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 corresponding trigger input (Trig. In 1...4). The trigger inputs are normalled top down. The minimum trigger level is +2.5V (up to max. +12V).
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

Module A-179-2 can be used to convert different illumination intensities into corresponding analog voltages and a gate signal derived from the analog voltage. It's the successor of the obsolete module A-179.
A light sensitive resistor (LDR) converts the illumination of the internal light sensor into a corresponding analog control voltage. The internal sensor is located at the front panel. Instead of the internal sensor a remote sensor can be connected via a standard patch cable to the module (ext.Sens. socket). An external sensor with a 2 m patch cable (A-100C200) is included. The external sensor is mounted on a small pc board which is equipped also with a 3.5 mm jack socket. The nut of the socket can also be used to mount the external sensor.

The module A-179 is similar to the Theremin module A-178 but uses the illumination intensity instead of the distance between hand and antenna for generating the analog voltage.
One can choose between passive control by covering/shading the sensor via hand or body, or active control by using e.g. a pocket lamp or flashlight. For this two versions of output voltages are available (CV Out + und CV Out -).

The module has these controls and in/outputs available:

ext. Sens.: by means of a standard patch cable the external sensor can be connected to this socket. In this case the internal sensor is turned off.
CV Offset: control to adjust the output voltage which is assigned to a certain illumination (e.g. 0V for complete darkness)
CV Level: control that is used to adjust the sensitivity of the generated output voltage (i.e. how much a certain difference in brightness affects the output voltage)
Gate Threshold: control that is used to adjust the threshold for the generation of the gate signal, an internal jumper is used to define if the gate signal is derived from the CV Out+ or CV Out- voltage.
CV Out+: positive control voltage output, increasing brighness causes the increase of the voltage at this output
CV Out+: negative control voltage output, increasing brighness causes the decrease of the voltage at this output
LED CV Out: bipolar LED (red/yellow) as display for the CV outputs
Gate: gate output with LED display

controlling any voltage controlled parameter e.g. pitch or pulswidth of a VCO, filter frequency or resonance of a VCF, loudness of a VCA, time of an envelope generator, frequency of a VCLFO
triggering activities via gate with adjustable threshold, e.g. starting an envelope, starting/stopping a sequencer or any switching function (e.g. with A-150-1 or 151).
Conversion into MIDI control change messages is possible with the A-192-2.

Module A-182-4 is a simple passive module that contains two mechanical rotary switches with 4 positions each. According to the position of the control knob socket 1, 2, 3 or 4 is connected to the common socket C.
As the module is fully passive it works bidirectional, i.e. the sockets 1...4 can be inputs and then C is the output. The other way round C can be the input and the sockets 1...4 are the outputs.
By means of an internal jumper the terminals C of both switches can be connected. That way the module can be used as kind of a miniature 4x4 matrix. Rotary switch A is e.g. used to select one of the four sockets 1...4 as input and this signal is sent to one of the four sockets 1...4 of switch B.


switching of audio or control signals in the modular system without the need to unplug and plug patch cables (i.e. no signal interruptions)
building a small 4x4 miniature switch matrix

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