LRR Eurorack Modules

JVCA Eurorack Module

This Eurorack module contains 2 JFET based voltage-controlled amplifiers (VCA). VCA’s are a core component in synths. They’re commonly used in conjunction with an envelope generator for shaping
sounds, or with two oscillators for tone synthesis. The inputs and outputs are buffered using fast professional audio grade op-amps to maintain signal integrity and performance.


SizeWidth: 4 HP
Depth: 42 mm
Power360 mW
12 V15 mA
-12 V15 mA
1 (knob)User control knob/
CV DC offset
2 (CV)Control Voltage
0 to 5 V range
3 (SIG:IN)Input Signal
-5 to +5 V range
4 (SIG:OUT)Output Signal


The module uses a standard 10 pin Eurorack connector with polarity marked

Inputs and Outputs

1. Knob

Adds a DC offset from 0 to 5 volts to the control voltage.

2. CV

This is the control voltage gain input, and it is normalized to 0 V. The recommended input range is 0 to 5 V. Voltages less than 0 will have the same gain as 0 V, and Voltages greater than 5 V will have the same gain as 5 volts.

3. Sig:In

The signal input is DC-coupled and will accept audio or CV signals. The recommended input range is -5 to +5 V. Voltages outside this range will cause increased distortion.

4. Sig:Out

Signal output

Inputs are tolerant to voltages from -12 V to + 12 V. Exceeding this range will damage the module.

Gain Response

The response of the VCA is exponential. A representative plot showing gain vs control voltage is shown in Figure 1.

Figure 1. Gain vs Control Voltage

LRR Eurorack Modules

Mid Side Module

This Eurorack module enables mid side processing. The top portion of the module converts left and right stereo signals into mid and side components for filtering or other effects. The bottom portion of the module converts the mid and side signals back into left and right stereo components. Mid and Side out are internally connected to Mid and Side in respectively (normalized). These connections are severed if cables are connected to the Mid and Side inputs respectively. The module uses professional audio quality amplifiers which are both fast and have low noise insertion so the module imparts minimal color to the processed signals.


Width4 HP 
Depth54.5 mm
Power0.38 W
+12 V16 mA
-12 V16 mA

Channel Definitions

L<Left in (Lin)
R<Right in (Rin)
M>Mid out (Lin + Rin)/2
S>Side out (Lin– Rin)/2
M<Mid in (Min)
S<Side in (Sin)
L>Left out (Min + Sin)
R>Right out (Min – Sin)


The module uses a standard 10 pin eurorack connector with polarity marked. 

Filter ideas

Uniform Filtering

Separate Mid and Side apply similar filters to both channels before remixing. This minimizes unwanted distortions in left and right channels from using filters that aren’t perfectly matched.

Center the base

Separate mid and side, then apply a high pass filter to the side channel before remixing to left and right. 

Add space

Separate Mid and Side, then apply reverb to the side channel, before remixing to left and right

Control Voltage Mixing

Half Differential+