Dual Bernoulli Gate (Either/Or)

Posted on February 10, 2022 by Harald

This module takes the incoming gate or trigger and routes it to either of its two outputs. The distribution is software driven, according to a random coin toss. You can select the probability distribution with a potentiometer and an input control voltage. The potentiometer voltage and the control voltage are added together. The probability goes from 0% to 100% at output A and from 100% to 0% on output B.

Specs and features

Randomly skip Gates and Triggers
Probability distribution voltage controlled
Dual Bernoulli gate
Runs on +/-12V and +/-15V
Power consumption below 20mA positive rail. 5mA negative rail.

The documentation and the Gerber files for download can be found in my website.

**Bernoulli Gate: Schematic control board**

**Bernoulli Gate: Schematic main board**

**Bernoulli Gate: Populated control board**

**Bernoulli Gate: Populated main board**

Scanning Mixer

Posted on January 12, 2022 by Harald

This scanning mixer is derived from the work of Jürgen Haible and Don Tillman with a lot off additions, changes and expansions.. The mixer is able to scan through four inputs with variable depth ans position. Manually and CV controlled. You can overdrive the individual channel nicely to add some overtones per channel. Rate, depth and scan amount are voltage controllable. The mixing level is controlled with sliders and voltage controllable as well. The four channels are summed into an output channel with similar controls.

The scanning mixer comes in two flavours linear and logarithmic. The linear scan gives a more smooth transition between the channels. The logarithmic scan gives a steeper separation between channels. All channels are DC coupled. So you can get interesting slowly moving CV textures when slowly scanning through different LFO outputs. When the depth potentiometer is set to zero you can use this module as simple voltage controlled mixer

Specs and features

Four input channels
DC coupled
Overdrive per channel
Variable scan depth and position
Voltage controlled rate, depth and scan amount
Mixing level voltage controllable
Power consumption below 80mA each rail

The documentation and the Gerber files for download can be found in my website.

There are to much schematic to post here. Please refer to my website. Only pictures here.

Active Case Connector

Posted on January 9, 2022 by Harald

When using different cases it is quite inconvenient to run lots off long patch cables between them. With this pair of modules you can reduce the amount of patch cables used between cases. This modules allows to use ribbon cables between cases. The connections are active buffered with OpAmps, so they are unidirectional. To connect cases in both directions (send and return) you need two pairs of this modules.

Specs and features

Eight active unidirectional connections
Runs on +/-12V and +/-15V
Power consumption below 20mA each rail

The documentation and the Gerber files for download can be found in my website.

**Active Case Connector: Schematic send**

**Active Case Connector: Schematic receive**

**Active Case Connector: Populated PCB**

Rotating Gate

Posted on December 6, 2021 by Harald

With this module you can distribute the incoming gate or trigger up to eight outputs. The distribution is software driven. You can select the amount of the used outputs from zero to eight with a potentiometer and an input control voltage. The potentiometer voltage and the control voltage are added together. The mode potentiometer and the mode control voltage selects the algorithm for the distribution. As for the moment (2021 Nov.) only one mode is implemented. Rotating upwards. Any suggestions or programs are welcome.

Specs and features

Gate/Trigger distribution up to eight targets.
Number of used outputs voltage controlled
Distribution algorithm voltage controlled
Runs on +/-12V and +/-15V
Power consumption below 20mA positive rail. 5mA negative rail.

The documentation and the Gerber files for download can be found in my website.

**Rotating Gate: Schematic control board**

**Rotating Gate: Populated control PCB**

12dB Multimode VCF

Posted on November 30, 2021 by Harald

This is the Eurorack version of my NGF 12dB Multimode VCF.This filter type is widely used in many synthesizers. You can find it in Electronotes or in the SEM modules and in many other synthesizers as well. Nonetheless I have made some changes and adds. I wanted the filter to sound clean with no feedback and the feedback going from soft to very harsh. And usable for pinging (percussion). So I used the the CA3280 for good clean audio (You can use the newly available AS3280 instead). And added a voltage controlled feedback loop going from soft to harsh. This can give the filter a harsh sound and a lot of character. You can adjust the this behavior over a wide range with the calibration trimmers or changing one resistor and capacitor.

Specs and features

12dB voltage controlled multimode filter
Two inputs for easy mixing
Low pass, high pass, band pass and notch filter output
Positive and negative ENV control with sign changer
Temperature compensation with KTY81-110
CV inputs for linear TM, log TM, envelope, V/Oct tracking and emphasis
Runs on +/-12V and +/-15V (with minor resistor value changes for best performance)
Power consumption around 80mA each rail

The documentation and the Gerber files for download can be found in my website.

**12dB Multimode VCF: Control board schematic**

**12dB Multimode VCF: Populated control PCB**

**12dB Multimode VCF: Populated main PCB**

Matrix Mixer

Posted on November 25, 2021 by Harald

This is a 4 x 4 matrix mixer with switches for unipolar/bipolar mode for each column. Unipolar means that the controls work as attenuators. Bipolar means that the controls work as attenuverters. In this mode the amplification is zero in the middle position of the corresponding potentiometer. Turning the knob counterclockwise from the center position the signal is subtracted from the output sum. Turning the knob clockwise from the center position the signal is added to the output sum. The module is DC-coupled and can be used for audio and control voltage mixing.

Specs and features

4×4 Matrix
Switchable unipolar or bipolar mode
Power consumption below 30mA each rail

The documentation and the Gerber files for download can be found in my website.

**Matrix Mixer: Schematic control board**

CV Mover quad

Posted on October 8, 2021 by Harald

A companion for my other quad modules. Especially for my Quad LFO. You can use it as attenuator, attenuverter, CV Source and, most important, for offsetting bipolar control voltages to make them unipolar, positive or negative. The module is DC coupled, so you can use it for DC and AC. It is possible to offset the input with +/- 2.5V. The offset is signaled with diodes. There is an inverted output added as well. The main usage is for processing bipolar LFO voltages into unipolar control voltage inputs. If you have a LFO with +/- 5V output and want to make it unipolar set the input to halve and the offset to +2.5V. The output is then from 0..5V and 0..-5V at the negative output. You can easily adapt the module to other offset voltages with a few resistor changes.

Specs and features

Attenuator
Inverted and non- inverted output
Attenuverter
+/- 2.5V offset
Runs on +/-12V and +/-15V
Power consumption below 20mA each rail

The documentation and the Gerber files for download can be found in my website.

CV Mover quad: scheamtic — **CV Mover quad: Schematic**

Scaled voltage reference with octave and semitone steps

Posted on September 6, 2021 by Harald

**Scaled Voltage Reference: Front view**

This module provides high precision CV outputs in 1V (octaves) and 83,3mV (semitones) steps. The 1V output goes from -5 to +5V. The 83,3mV steps goes from -5 to plus 5 steps (semitones). This module is thought for all who are missing octave switches in some modules. Especially in VCO. With this module you can switch octaves and semitones as well.

Specs and features

High precision output from -5V to +5V in 1V steps (octaves)
High precision output in 83,3mV steps, +/- 5 steps (semitones)
Runs on +/-15V and +/-12V
Power consumption around 30mA each rail

The documentation and the Gerber files for download can be found in my website.

**Scaled Voltage Reference: Schematic control board**

**Scaled Voltage Reference: Schematic main board**

**Scaled Voltage Reference: Populated control PCB**

**Scaled Voltage Reference: Populated main PCB**

Multi Phase Waveform Animator

Posted on June 15, 2021 by Harald

This is my take on a multi phase waveform animator as described in EN#87 pg.3 ff by Bernie Hutchins. This module takes a single sawtooth waveform and then uses nine phase shifters to provide shifts from 0° to 360°. These shifts are controlled each by an independent oscillator which operates on a frequency of about 0.01Hz to 1.0Hz. The nine shifted waveforms are then mixed back together, along with original, to a composite sound. The volume of all phase shifted waveforms and the original are controlled with potentiometers. So you can dial in any amount of animation you like. You can choose from a variety of frequencies for the phase shifters. The method used here is described in EN#40 by Ralph Burhans. Ralph found that if you space frequencies at the fifth root of 2.1, you get no harmonic overlap over a 10 octave range. This is important because we don’t want to produce patterns which will repeat and be detected by our ears to keep the sound animated. As you can see in the screenshots you can use this module for other waveforms as well.

Specs and features

Nine independent phase shifters
Volume control for all phase shifted waveforms
Takes a lot more then only sawtooth inputs
Runs on +/-15V and +/-12V
Power consumption around 35mA each rail

The documentation and the Gerber files for download can be found in my website.

**Multi Phase Waveform Animator**: **Schematic control board**

**Multi Phase Waveform Animator**: **Schematic main board** 01

**Multi Phase Waveform Animator**: **Schematic control board** 02

**Multi Phase Waveform Animator**: **Populated control board**

**Multi Phase Waveform Animator**: **Populated main board**

**Multi Phase Waveform Animator**: **Back view**

**Multi Phase Waveform Animator**: **Side view**

BPM Generator 20..2400 BPM with dividers

Posted on May 10, 2021 by Harald

This is the enhanced version of my BPM-Generator in combination with my Clock Divider 2..8 and Clock Divider with primes adapted for Eurorack. The range goes from 20BPM up to 2400BPM. Pulses at 5V/20ms. All 16 outputs are synchronized and work in parallel. Divisions are 1, 2, 3, 4, 5, 6, 7, 8, 11, 13, 17, 19, 23, 29, 31 and 37. You have a start/stop input for the BPM generator and a reset input for the dividers. A 4 digits display shows the current BPM. You can store the latest timing with keypress.

Specs and features

20..2400 BPM
All outputs 5V/20ms
16 outputs
Start/stop input
Divider reset input
4 digit display
Power consumption around 5mA negative rail, 50mA positive rail

The documentation and the Gerber files for download can be found in my website.

**BPM Generator 20..2400 BPM with dividers: Populated control PCB**

**BPM Generator 20..2400 BPM with dividers: Populated control PCB backside**

**BPM Generator 20..2400 BPM with dividers: Populated main PCB**

**BPM Generator 20..2400 BPM with dividers: Side view**

**BPM Generator 20..2400 BPM with dividers: Back view**

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Analog Synthesizer DIY

Category Archives: Eurorack

Dual Bernoulli Gate (Either/Or)

Specs and features

Scanning Mixer

Specs and features

Active Case Connector

Specs and features

Rotating Gate

Specs and features

12dB Multimode VCF

Specs and features

Matrix Mixer

Specs and features

CV Mover quad

Specs and features

Scaled voltage reference with octave and semitone steps

Specs and features

Multi Phase Waveform Animator

Specs and features

BPM Generator 20..2400 BPM with dividers

Specs and features