Quad Ringmodulator

Quad Ringmodulator: Front view
Quad Ringmodulator: Front view

This is the 12V Euro version of my NGF dual version. It uses the now obsolete LM1496 balanced modulator -demodulator. But you can still source them and I have some in my stock. So I decided to make a PCB and module. I started with the original Elektor Formant schematic published in “Formant Erweiterungen” p35ff. I left out the microphone and envelope follower part because I already have such modules. I have added input buffers and raised the signal level to my 10Vpp used throughout my system.

Specs and features

  • Quad Ringmodulator
  • 10Vpp input and output
  • Runs on +/-12V and +/-15V
  • Power consumption around 70mA each rail

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

Quad Ringmodulator: Schematic control board
Quad Ringmodulator: Schematic control board
Quad Ringmodulator: Schematic main board
Quad Ringmodulator: Schematic main board
Quad Ringmodulator: Populated control PCB
Quad Ringmodulator: Populated control PCB
Quad Ringmodulator: Populated main PCB
Quad Ringmodulator: Populated main PCB
Quad Ringmodulator: Back view
Quad Ringmodulator: Back view
Quad Ringmodulator: Side view
Quad Ringmodulator: Side view

Stereo Mixer

Stereo Mixer:Front view
Stereo Mixer:Front view

This is a 3 in 1 stereo mixer with normalized left to right inputs. The module is DC-coupled and can be used for audio and control voltage mixing.

Specs and features

  • 3 in 1 Stereo mixer
  • Left input normalized to right input
  • DC coupled
  • Power consumption below 20mA each rail

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

Stereo Mixer: Schematic
Stereo Mixer: Schematic

Nothing special here. Simple, straight forward mixer design.

Stereo Mixer: Populated control PCB
Stereo Mixer: Populated control PCB
Stereo Mixer: Front side view
Stereo Mixer: Front side view
Stereo Mixer: Back view
Stereo Mixer: Back view
Stereo Mixer: Sde view
Stereo Mixer: Sde view

Scanning Mixer

Scanning Micer: Front view
Scanning Micer: Front view

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.

Scanning Mixer: Control PCB top
Scanning Mixer: Control PCB top
Scanning Mixer: Control PCB back
Scanning Mixer: Main PCB 01 lin
Scanning Mixer: Main PCB 01 lin
Scanning Mixer: Main PCB 01 log
Scanning Mixer: Main PCB 01 log
Scanning Mixer: Main PCB 02
Scanning Mixer: Main PCB 02
Scanning Mixer: Half front
Scanning Mixer: Half front
Scanning Mixer: Back
Scanning Mixer: Back
Scanning Mixer: Side
Scanning Mixer: Side

Matrix Mixer

Matrix Mixer: Front view
Matrix Mixer: Front view

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

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

Utility Mixer I

Utility Mixer I
Utility Mixer I

This is an often used utility module. The mixer comes in handy for mixing CV sources. The mixer is DC coupled, so you can use it for DC and AC mixing. The input impedance is constant 1MOhm. The input signals are amplified by a maximum factor of two. It is possible to offset every input with +/- 5V. The offset is signaled with LED’s for every channel and for the summing output. The outputs are normalized, so you can remove selected channels from the output mix. The summed output has a -6dB switchable attenuator. There is an inverted summed output added as well. The added volume indicator us useful for finding the appropriate signal level.

Specs and features

  • Three inputs, three outputs
  • Inverted and non- inverted summed output
  • 2x amplification
  • +/- 5V offset for every channel
  • -6dB switch
  • Volume indicator
  • Normalized outputs
  • 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.

Utility Mixer I: Main board
Utility Mixer I: Main board
Utility Mixer I: Control board
Utility Mixer I: Control board

Control board: Straight forward design. The mixer is completely DC coupled. So you can use it for CV mixing as well as audio mixing. IC1B,C,D buffers the three inputs and and keeps the input impedance constant. P2, P4, P6 sets the amplification from zero to 2X. P1, P3, P5 sets the offset voltage. The LED indicates the offset and signal level.

Main board: IC3B, IC4B, IC6B adds the offset voltage and the signal. IC1C, IC1D, IC1B, IC1B drive the low current LED. IC2A sums the signals and drives the negative output. IC2B drives the positive output.

Utility Mixer I: Populated control board
Utility Mixer I: Populated control board
Utility Mixer I: Populated main board
Utility Mixer I: Populated main board
Utility Mixer I: Side view
Utility Mixer I: Side view
Utility Mixer I: Back view
Utility Mixer I: Back view

Mixer, DC coupled with volume indicator

Mixer: Front view
Mixer: Front view

This is an often needed utility module. The 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. The added volume indicator us useful for finding the appropriate signal level. The volume indicator is optional. You can leave it out with no problems for the other functions.

Specs and features

  • Five inputs
  • Inverted and non- inverted output
  • Volume indicator (optional)
  • 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.

Mixer: Schematic control board
Mixer: Schematic control board

Control board: Straight forward design. The mixer is completely DC coupled. So you can use it for CV mixing as well as audio mixing. IC1D sums the five inputs and inverts the signal. P3 is used to adjust the overall signal level. IC1B inverts the signal again. IC1C and IC1A buffers the outputs.

Mixer: Level indicator
Mixer: Level indicator

Level indicator: The circuitry around IC2 build an precision full wave rectifier. The output is smoothed with C1. The parts around the BC560C build a constant current source for driving the LED’s. The comparator LM393 (IC1A/B) switches the LED on and off according to the input level.

Mixer: Populated control PCB
Mixer: Populated control PCB
Mixer: back view (with populated level indicator board)
Mixer: back view (with populated level indicator board)