MRG VCA Assembly Guide

The MRG VCA uses only through hole components.

Its build should be considered of medium difficulty given the number of components and steps required.

Theory of operation:

  1. If you bought the PCB+Panel+IC only, acquire needed components (See Bill of Materials. All components used in this guide are already included in the full DIY kit.
  2. Build the Main PCB.
  3. Build the Front PCB.
  4. Install the front panel.

Main PCB build

Step A1. Start by soldering all horizontal resistors and the diode.

vca pcb

Step A2. Solder all ceramic capacitors.

vca pcb

Step A3. Solder the linear voltage regulators and the electrolytic capacitors.

vca pcb

Step A4. Solder the two TL072 ICs. If desired, you can solder IC sockets at this stage (two 8-pin), and insert the ICs in the sockets later on.

vca pcb

Step A5. Solder the AS3360 IC and the 10-pin header Eurorack connector.

vca pcb

Everything apart from the two 14-pin headers are soldered on the board now. It is time to solder the front PCB.

Front PCB Build

Step C1. Check the alignment of the PCB (label U1 is the top row), arrange the jack sockets and the potentiometers.

vca pcb

Step C2. Solder the components. Tip: in order to be sure to align the components to the front panel, install the front panel as in photo below and solder the components on the back.

vca pcb

Step C3. Solder the socket headers. Tip: In order to align the Main PCB's pin headers to the Front PCB's socket headers, assemble the two PCBs together, as in picture, and solder them in place.

vca pcb

Congratulations! The build is nearly done. All that's left is installing the front panel.

Final Module Assembly

All that's left now is to install the front panel, using nuts and washers to keep it attached, and adding the knobs to the potentiometers.


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Bill of Materials

This is the complete list of components needed to build the module if you buy panel + PCB + IC only.

Note: Use of 1% tolerance resistors highly recommended.

ComponentQuantityPackage

ICs:

TL072BCP2

Resistors (3.5mm, 1/8W or more):

100k6
51k2
1k4
10k2
20k2
30k4

Ceramic Capacitors (5mm pitch):

4.7nF1
100nF8
220nF2

Other Capacitors:

22uF Electrolythic Capacitor2

Other Components:

78L051
79L051
1N41488
14 Pin 2 Row Header2
14 Pin 2 Row Socket2
10 Pin 2 Row Header1
B100K3Alpha 9mm T18 Potentiometer
PJ398SM 3.5mm Jacks6