Active Slider Bank (command one)

Posted on March 29, 2022 by Harald

This utility module gives you a wide range of variable and adjustable control voltages from -10V to +10V. This only depends on the knob and slider setting and patching within itself. If used with external input it can attenuate and offset the incoming signal. I use this module for steering modules which lacks of attenuator at the inputs or in greater patches for applying control voltages to far away modules. It is quite comfortable to have the controls in the first row of your case and not somewhere in the messy patch hardly in reach for your hands

Specs and features

Variable and adjustable control voltages from -10V to +10V
Six independent active attenuator with external signals
Positive and negative offset for external signals
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.

**Command one: Schematic control board**

**Command one: Populated control PCB back**

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**

Track (Sample) and Hold

Posted on November 19, 2021 by Harald

One more module for my Shakuhachi to Synths project. Not exclusively of course. This is a Track and Hold. Which is quite useful for other patches as well. In the Shakuhachi patch it is used to suppress an incomplete pitch to voltage conversion from the Pitch to voltage converter when the player stops blowing. The module tracks the incoming (control) voltage as long as the gate input is high. When the gate goes low the output voltage is kept. The module is DC coupled to track slowly moving voltages. For this one I have used some obsolete parts, which I had laying around. So, if you want to build it, make sure that you can get those parts. You can use it as Sample and Hold as well. Instead of a gate apply a trigger at the gate input.

Specs and features

Track or Sample and Hold
DC coupled
Gate input with LED
Signal input
Signal output
Threshold
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.

**Track (Sample) and Hold: Populated PCB**

Shakuhachi 2 Synth Project

Posted on November 18, 2021 by Harald

**Shakuhachi to synth project: Current patch**

I have made some updates to my Shakuhachi to Synth project page. It presents the current patch and some more modules. The project is still ongoing.

Shakuhachi to synth project: Current patch blockdiagram — **Shakuhachi to synth project: Current patch, blockdiagram**

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**

Voltage controlled AVR LFO with variable symmetry

Posted on October 7, 2021 by Harald

**Voltage controlled AVR LFO: Front view**

This is an old project dated back to December 2017. It was intended to learn some basics about the hard- and software of the ATMEGA series from AVR. It is kept simple. Just three analog inputs, one interrupt input and PWM output with filter are used. It is up to you what software you want to run on it. Here I made a simple voltage controlled VCO with variable symmetry. Speed, waveform and symmetry are voltage controlled. So you can change the triangle from ramp up to triangle to ramp down. Or make one halve of the sine very small. See screenshots below. This software was mainly written to test the hardware. To my surprise it worked sufficiently well for a LFO. So I leave it as is for the moment. No fancy accumulation with fixed point arithmetic and increment interpolation. Of course there is a lot room for improving the software. I know.

Specs and features

Voltage control for speed, waveform, symmetry
Bipolar and unipolar output
Square, triangle, sine, ramp up, ramp down waveform
20MHz crystal
19.5kHz PWM 10bit resolution
Runs on +/-15V and +/-12V
Power consumption around 30mA positive, 5mA negative rail

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

**Voltage controlled AVR LFO: schematic 01**

**Voltage controlled AVR LFO: schematic 02**

**Voltage controlled AVR LFO: Populated PCB**

**Voltage controlled AVR LFO: Screenshot waveform**

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**

Trapezoid quadrature through zero LFO

Posted on August 9, 2021 by Harald

This is my Trapezoid quadrature through zero LFO. Derived from my Trapezoid quadrature through zero VCO. Still using the trapezoid VCO core designed by Don Tillman (used with permission). I found the original article and schematic about the Trapezoid VCO on Don Tillman’s site (Link to original article from 19 July 2003). The article consists off three parts with the core implementation in part 2. I kept the basic idea and changed nearly everything else. I use an other exponentiator scheme and temperature stabilization. Another reference voltage device is used. And quadrature square outputs are implemented. As well as the additional waveforms triangle, sine, ramp up and ramp down. For the LFO I made a few changes. I removed the pulse output and added the missing ramp up and ram down outputs for 180deg and 270deg. Everything else is kept the same as in my Quadrature VCO. This LFO runs from zero Hertz way up in the audio range.

Specs and features

Runs from zero Hertz to audio range.
Trapezoid quadrature output
Square quadrature output
Triangle quadrature output
Sine quadrature output
Ramp up quadrature output
Ramp down quadrature output
Through zero modulation
V/Oct, FM log and trough zero CV input
Temperature compensated
Runs on +/-15V and +/-12V
Power consumption around 110mA each rail

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

**Trapezoid quadrature through zero LFO: Trapezoid quadrature output**

**Trapezoid quadrature through zero LFO: Trapezoid square output**

**Trapezoid quadrature through zero LFO: Trapezoid ramp up output**

**Trapezoid quadrature through zero LFO: Trapezoid ramp down output**

**Trapezoid quadrature through zero LFO: Trapezoid triangle output**

**Trapezoid quadrature through zero LFO: Trapezoid sine output**

**Trapezoid quadrature through zero LFO: Populated control board**

**Trapezoid quadrature through zero LFO: Populated main board 01**

**Trapezoid quadrature through zero LFO: Populated main board 02**

Trapezoid quadrature through zero LFO: back view — **Trapezoid quadrature through zero LFO: Back view**

**Trapezoid quadrature through zero LFO: Side view**

CV Mover – Euro

Posted on March 14, 2021 by Harald

A small but versatile module. 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.

Specs and features

Attenuator
Inverted and non- inverted output
Attenuverter
+/- 2.5V offset
Runs on +/-12V and +/-15V
Power consumption below 10mA each rail

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

Sequencer Nostalgia

Posted on January 18, 2021 by Harald

This was my first build when I came back to SDIY. A three row/16 step sequencer. Completely build on stripboard. Still working after all this years. Only hand sketched schematics. Nothing to publish. Pictures only.

**Sequencer three rows/16 steps: front**

Sequencer: Clock close up back — **Sequencer: Clock close up** **back**

VocLog

Analog Synthesizer DIY

Category Archives: CV Sources

Active Slider Bank (command one)

Specs and features

Dual Bernoulli Gate (Either/Or)

Specs and features

Track (Sample) and Hold

Specs and features

Shakuhachi 2 Synth Project

CV Mover quad

Specs and features

Voltage controlled AVR LFO with variable symmetry

Specs and features

Scaled voltage reference with octave and semitone steps

Specs and features

Trapezoid quadrature through zero LFO

Specs and features

CV Mover – Euro

Specs and features

Sequencer Nostalgia