CV Mover quad

CV Mover quad: Front view
CV Mover quad: Front view

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
CV Mover quad: Populated PCB
CV Mover quad: Populated PCB
CV Mover quad: Back view
CV Mover quad: Back view
CV Mover quad: Side view
CV Mover quad: Side view

Voltage controlled AVR LFO with variable symmetry

Voltage controlled AVR LFO: Front view
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 01
Voltage controlled AVR LFO: schematic 02
Voltage controlled AVR LFO: schematic 02
Voltage controlled AVR LFO: back
Voltage controlled AVR LFO: back
Voltage controlled AVR LFO: Populated PCB
Voltage controlled AVR LFO: Populated PCB
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform
Voltage controlled AVR LFO: Screenshot waveform

Scaled voltage reference with octave and semitone steps

Scaled Voltage Reference: Front view
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 control board
Scaled Voltage Reference: Schematic main board
Scaled Voltage Reference: Populated control PCB
Scaled Voltage Reference: Populated control PCB
Scaled Voltage Reference: Populated main PCB
Scaled Voltage Reference: Populated main PCB
Scaled Voltage Reference: Side view
Scaled Voltage Reference: Side view
Scaled Voltage Reference: Side view
Scaled Voltage Reference: Side view

Trapezoid quadrature through zero LFO

Trapezoid quadrature through zero LFO: Front view
Trapezoid quadrature through zero LFO: Front view

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 quadrature output
Trapezoid quadrature through zero LFO: Trapezoid square 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 up output
Trapezoid quadrature through zero LFO: Trapezoid ramp down output
Trapezoid quadrature through zero LFO: Trapezoid ramp down output
Trapezoid quadrature through zero LFO: Trapezoid triangle output
Trapezoid quadrature through zero LFO: Trapezoid triangle output
Trapezoid quadrature through zero LFO: Trapezoid sine output
Trapezoid quadrature through zero LFO: Trapezoid sine output
Trapezoid quadrature through zero LFO: Populated control board
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 01
Trapezoid quadrature through zero LFO: Populated main board 02
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
Trapezoid quadrature through zero LFO: Side view

Voltage controlled Mixer-VCA

Voltage controlled mixer-VCA: Front view
Voltage controlled mixer-VCA: Front view

This is basically a combination of 6 VCA configured as a mixer. The five inputs can be used as individual linear VCA or as input channels to the mixer output. All five input channels and the mixer output are voltage controlled. The control voltage inputs for the input channels are normalized so you can modulate all five channels with the same control voltage or group them to your needs. The sliders controls the amount of the modulation per channel. The inputs are normalized as well. This makes for a nice voltage controlled overdrive when used. A level indicator shows the output signal at the summed output. The summed output is voltage controlled as well. Instead of the here used CA3280 (I am using up some NOS) you can use the new available AS3280.

Specs and features

  • Five voltage controlled inputs
  • Five independent VCA
  • Voltage controlled output
  • Level indicator
  • Power consumption around 75mA each rail

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

Voltage controlled mixer-VCA: Schematic control board
Voltage controlled mixer-VCA: Schematic control board
Voltage controlled mixer-VCA: Schematicmain board
Voltage controlled mixer-VCA: Schematic main board

On the schematics you can see 6 VCA with linear control current sources. Just as it is done over and over again. Plenty explanations on the web.

Voltage controlled mixer-VCA: Populated controö board top
Voltage controlled mixer-VCA: Populated controö board top
Voltage controlled mixer-VCA: Populated control board back
Voltage controlled mixer-VCA: Populated main board
Voltage controlled mixer-VCA: Populated main board
Voltage controlled mixer-VCA: Side view
Voltage controlled mixer-VCA: Side view
Voltage controlled mixer-VCA: Side view

Thomas Henry’s MPS

Thomas Henry's MPS: Front view
Thomas Henry’s MPS: Front view

This is my take on the Mega Percussion Synthesizer designed by Thomas Henry. With many thanks to Thomas who kindly gave me the permission to publish it here for DIY. I have made two minor changes which I found useful. First I added input buffers to all four sections of the circuitry, because this eliminates the influence of the potentiometer adjustment to each other. And I changed the circuitry around the CV input and the impact/noise switch. The CV input is now added to the impact/noise switch, with a neutral middle setting for the original behavior. The locked mode is left out.

Specs and features

  • Same as the original
  • 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 (link).

Thomas Henry's MPS:  Schematic control board
Thomas Henry’s MPS: Schematic control board
Thomas Henry's MPS: Schematic main board
Thomas Henry’s MPS: Schematic main board
Thomas Henry's MPS: Populated control board
Thomas Henry’s MPS: Populated control PCB
Thomas Henry's MPS: Populated main PCB
Thomas Henry’s MPS: Populated main PCB
Thomas Henry's MPS: Back view
Thomas Henry’s MPS: Back view
Thomas Henry's MPS: Side view
Thomas Henry’s MPS: Side view

Multi Phase Waveform Animator

Multi Phase Waveform Animator: Front view

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: Populated main board
Multi Phase Waveform Animator: Back view
Multi Phase Waveform Animator: Side view

BPM Generator 20..2400 BPM with dividers

BPM Generator 20..2400 BPM with dividers: Front view
BPM Generator 20..2400 BPM with dividers: Front view

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
BPM Generator 20..2400 BPM with dividers: Populated control PCB backside
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: Populated main PCB
BPM Generator 20..2400 BPM with dividers: Side view
BPM Generator 20..2400 BPM with dividers: Side view
BPM Generator 20..2400 BPM with dividers: Back view
BPM Generator 20..2400 BPM with dividers: Back view

Small Mixer for Eurorack

Mixer small: Front view
Mixer small: Front view

It is mostly sufficient to mix only two or three audio or control voltages together to enhance your sound or the sound animation. So this small mixer comes in handy for mixing CV sources and audio sources as well. This version is DC coupled, so you can use it for AC and DC mixing. There is an inverted output added. You can reverse the DC-CV mix with it or experiment with feedback loops in the audio domain.

Specs and features

  • Three inputs
  • Inverted and non- inverted output
  • Runs on +/-12V and +/-15V
  • Power consumption below 20mA each rail

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

Mixer small: Schematic control board
Mixer small: Schematic control board
Mixer small: Schematic main board
Mixer small: Schematic main board
Mixer small: Populated control PCB
Mixer small: Populated control PCB
Mixer small: Populated main PCB
Mixer small: Populated main PCB
Mixer small: Back view
Mixer small: Back view
Mixer small: Side view
Mixer small: Side view

Sims style VCA for Eurorack

Sims style VCA: Front view
Sims style VCA: Front view

This is the Eurorack version of my Sims VCA. This VCA is AC coupled. I made my own implementation of the Sims-VCA introduced by Mike Sims in the EDN Magazine January 1995. With this architecture it is possible to achieve THD of 0,02%. Unfortunately I can not confirm the statement from Mike Sims that trimming the circuit for minimum THD achieves minimum control voltage feedthrough. Trimming for minimum THD causes an constant DC bias at the output. I have had to add a output capacitor to avoid the bias at the output. And you need test equipment to measure the THD for correct trimming. If you can not measure THD better build my DC-VCA. You can achieve 0,2 % THD there. Still good. Or, for Eurorack, my Quad VCA.

Specs and features

  • AC coupled, 0,02% THD
  • Two inputs
  • Lin and log response
  • CV 0..+5V
  • CV attenuator
  • Adjustable bias
  • Power consumption below 25mA each rail

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

Sims style VCA: Schematic control PCB
Sims style VCA: Schematic control PCB
Sims style VCA: Schematic main PCB
Sims style VCA: Schematic main PCB
Sims style VCA: Populated control PCB
Sims style VCA: Populated control PCB
Sims style VCA: Populated main PCB
Sims style VCA: Populated main PCB
Sims style VCA: Side view
Sims style VCA: Side view
Sims style VCA: Back view
Sims style VCA: Back view