Populate the yellow .1u capacitors in the positions marked CB etc. These capacitors give noise in the power rails a path to ground, "bypassing" the rest of the circuit. Hence the designator CB. Every CB part in the build is .1u, so the values are not marked on the PCB. These capacitors are not polarized.

Insert the IC sockets so that the notches on the sockets align with the markings on the PCB. You may want to secure these with tape before soldering.

There are two important things to note about the regulators. First, one side of the body is flat while the other is round. And second, one is 7812 (black top) while the other is 7912 (silver top).

Place the 7812 in U1 and the 7912 in U2. Place both of them so that the shape of the body matches the shape on the circuit board. Double check the positions and orientation, then solder and trim.

Place the inductors in their positions, solder, and trim. Inductors are not polarized.

The four 2200u capacitors are polarized, so they must be placed in a certain direction. The positive lead is slightly longer, while the negative lead is marked with a stripe on the body of the capacitor. Place the capacitors with the positive lead in the pad next to the "+" marking on the PCB. The two 4.7u capacitors are not polarized.

Place the XLR jacks. Most will snap in place, but you may need to use some tape if they fall out before soldering. Solder the jacks but do not trim the leads.

For this and all following test steps, connect the power before testing and disconnect the power after.

1. Set your multi-meter to read 20V DC.
2. Place the black probe on a GND test point. The black probe should go to a GND test point for all future tests.
3. Probe the +16V, -16V, +12V, and -12V test points with the red probe. The voltage should be within 0.5V of the rated voltage.

Pay close attention to which side the components should be populated on. On the CBs, the resistors and caps go on one side, while the switches and pots go on the other. Remember that the 100u caps are polarized.

C1_CB, C2_CB
100u cap (x2)

C3_CB, C6_CB
.15u cap (x2)

Markings: 2A154J

C4_CB, C7_CB
.1u cap (x2)

C5_CB, C8_CB
68n cap (x2)

Markings: 2A683J

Populate the various headers that connect the controls to the motherboard (MB). Again, note carefully the side to populate on. Also note that the shrouded headers CON2-CON4 must be inserted in a particular orientation.

CON2_CB
16-pin header

CON3_CB
12-pin header

CON4_CB
26-pin header

Pay close attention to the values marked on the back when placing the potentiometers (pots).

VR1_CB, VR2_CB
B50k pot (x2)

Markings: B503

VR3_CB
B10k pot

Markings: B103

Note that the rotary switches have a small round tab at 9 o'clock (if the logo is 12). This tab will mate with a hole in the mounting bracket, so it's very important that the switch be installed the correct way. Note that there circles on the PCB drawings that correspond to the tabs.

Insert the switches so that the tabs on the switches match those on the PCB. Then place the switches and board in the U-bracket to double check the orientation before soldering.

SW1_CB-SW3_CB, SW5_CB
2x6 switch (x4)

SW9_CB
4x3 switch

Install the switch caps before populating the switches on the small sub-board. Place the switches so that the E on the body aligns with the E on the PCB. Note the correct side before soldering. Also populate the 4-pin header on the opposite side of the board from the switches. Orient the header so the plastic posts are flush against the bottom of the sub-board.

SW6_CB-SW8_CB
DPDT switch (x3)

CON6B_CB
4-pin header

Fasten the sub-board to CB2 via the screws, standoffs, and nuts. Then solder the 4-pin header to CB2 and trim the excess leads.

4-40 screw 3/8" (x2)

4-40 nut (x2)

4-40 standoff 5/32" (x2)

For each wire on the harness, place the wire through the end of the terminal until the insulation runs against the small tab on the terminal. The exposed part of the wire should sit between the tab and the side of the terminal. Then, using a pair of pliers, crimp the part of the terminal that surrounds the insulated part of the wire. After crimping, check that the wire is held securely in the terminal and that you can't pull it out. Then solder the tinned end of the wire to the terminal.

Quick-connect terminal (x4)

The IN switch has three columns of pins: one for each pole of the switch and a third for the LED. The switch columns are labeled "NO" for normally open, "NC" for normally closed, and "C" for common. The LED column is labeled "L(+)" for LED power and "L" for ground. Assuming the switch is viewed from the back with the "IN" label upright, the left column is 1 and the furthest right column is 2.

On the plastic part of the wiring harness there is a small number to indicate pin 1. Note that for the first batches of kits, the colors of the wires are different from those shown in the photo.

For the jumper, use a leftover component lead.

• CON5 pin 1: C2
• CON5 pin 2: NO1
• CON5 pin 3: L
• CON5 pin 4: C1
• Jumper NO2 -> L(+)

Populate the ICs, headers, resistors, diodes, and capacitors. Place the ICs so that the notch or dot on the body corresponds with the notch on the socket and PCB. Place the headers so they match the orientation shown on the PCB. And note that the diodes and large capacitors are polarized.

Note that the 10k and 120R resistors have the same color code in opposite directions. Confirm the values for these resistors with a multi-meter before soldering.

C7
100u cap

C8
100p cap

C9, C10
3.3n cap (x2)

CON1
3-pin header

CON2
16-pin header

CON3
12-pin header

CON4
26-pin header

CON5
4-pin header

D1-D3, D11
1N4004 diode (x5)

IC1, IC7
LF347N opamp (x2)

You can hold the relays in place for soldering with tape or by bending the leads against the bottom of the PCB.

U3-U6
24V relays (x5)

Use the ribbon cable and IN switch wiring harness to connect CB2 and the IN switch to the MB.

1. Set the multi-meter to read continuity (the "beep mode").
2. Place the probes on the test points next to a relay (it doesn't matter which probe goes where).
3. Press the button on the CB associated with that relay. The meter should beep when the switches are pressed IN, except for the IN switch. For the IN switch, the meter should beep when the switch is out.
4. Repeat for each relay. Note that the two XFMR relays U3_1 and U3_2 are controlled by the same button.
5. Disconnect CB2 and the IN switch from the MB.

Note: Due to a bug on the v1.0 PCB, the MONO SC relay will not test correctly. You can skip testing this relay. The revision number is in the lower left corner of the main PCB. For v1.0 it says "1.0 2022."

Place the TRS jacks. Hold them in place with tape or by bending the leads, then solder and trim.

Place the XLR jacks. Most will snap in place, but you may need to use some tape if they fall out before soldering. Solder the jacks but do not trim the leads.

Populate the ICs, resistors, and capacitors. Do not populate the transformers yet. Remember that the large caps, ICs, and trimpots are polarized. Note: On version 1.0 of the PCB VR1's value is erroneously marked as 5k.

C11, C12, C20
22u cap (x6)

C13, C15, C19
100u cap (x6)

C14
22p cap (x2)

Markings: 22j

C16
220u cap (x2)

C17, C18
100p cap (x4)

Markings: bc 101

IC2, IC3
NE5532 opamp (x4)

RA1, RA2
10k array (x4)

VR1
50k trimpot (x2)

Markings: W503

1. Calibrate REW with a multi-meter.
1. Connect a TRS cable to the first output of your interface. This output might be called "1" or "L."
2. Open the Generator in REW and send a 60Hz, -10dBFS signal to the plug.
3. Set the multi-meter to read AC volts.
4. Probe the Tip and Ring of the plug and note the value.
5. Press "Calibrate Level" and enter the value.
2. Switch the dB unit to dBu. Then set the generator to 60Hz, +4dBu.
3. Connect the TRS plug to J5_1
4. On the L channel, place the probes on the BAL in and GND test points. Your meter should read between 1.1-1.3V.
5. Repeat steps 3-5 for the R channel.

Populate the ICs, diodes, resistors, capacitors, and trimpots. Remember that the large caps, diodes, ICs, and trimpots are polarized.

C21
22p cap (x2)

Markings: 22j

C22, C24
22u cap (x4)

C23
100p cap (x2)

Markings: bc 101

D4, D5
1N4148 diode (x4)

IC4
NE5532 opamp (x2)

VR2
50k trimpot (x2)

Markings: W503

This step assumes you are using the stock VCAs. If you are planning to use your own vintage VCA in the DBX 202 footprint, do not populate these VCAs. Instead follow the instructions for the Vintage VCA Mod.

Place the right-angle side of the 7-pin connectors through the VCA sub-boards from the front and solder them so that the sides of the black plastic posts sit flush with the PCB. Then install this assembly in the VCA1A positions.

VCA1A
2181C VCA PCB (x2)

VCA1A
12-pin header (x2)

1. Connect your interface to the L channel input and output.
2. Send a 1Khz, -10dBFS test signal.
3. Open Levels in REW. You should see your -10dBFS test signal on the Out meter and some level coming back in on the In meter.
4. Set unity gain by turning VR1 until the In meter matches the Out meter.
5. Repeat steps 2-5 with the R channel.

Populate the ICs, resistors, and capacitors. Remember that the large caps and ICs are polarized.

C25, C28
22p cap (x4)

Markings: 22j

C26
82n cap (x2)

Markings: 82nJ63

C27
3.3n cap (x2)

Markings: 3n3j100

C29
22u cap (x2)

IC5
NE552 opamp (x2)

1. Connect CB2 to the MB. Connect your interface to the L channel input. You do not need to connect to the output.
2. Send 60Hz, +4dBu test signal.
3. Set the meter to AC volts and probe the FILTER and GND test points on the L channel.
4. Turn the FILTER knob to positions 1-6 (later you will set the stop so that this is the furthest the switch can be turned). The value should start around ~1v at OFF, then go down, then back up, then finally end at 0V in the Ext. SC position.
5. Repeat steps 2-6 with the R channel.
6. Disconnect CB2 from the MB.

Populate the ICs, diodes, resistors, capacitors, and VCA. Note that C30, the diodes, ICs, and VCAs are polarized.

C30
6.8u cap (x2)

C31
22p cap (x2)

Markings: 22j

C32
100p cap (x2)

Markings: bc 101

D6-D10
1N4148 diode (x10)

IC6
LF347 opamp (x2)

VCA2
2181C VCA PCB (x2)

VCA2
12-pin header (x2)

Populate the diodes, resistors, capacitors, and trimpots. The tantalum capacitors in the Release section are polarized. The positive lead is longer and is marked with a "+". Note that C37 is a different value from the rest of the tantalums.

C33-C36, C38
.47u cap (x5)

Markings: 474L

C37
6.8u cap

Markings: 685H

VR3
5k trimpot

Markings: W502

Populate the diodes, resistors, capacitors, and trimpot. Note that the 10u NP capacitors are not polarized.

C39-C42
10u NP cap (x4)

C43
100p cap

D12, D13
1N4148 diode (x2)

VR4
50k trimpot

Markings: W503

1. Connect both CBs and the IN switch to the MB. Connect your interface to both inputs. Leave the outputs unconnected.
2. Set all controls CCW (counter-clockwise).
3. Engage the compressor with the IN button.
4. Send a 60Hz sine wave, +4dBu test signal. In the REW Generator, set the Output to 1+2 (this might also be called L+R). This option is at the bottom of the window, next to the Play button.
5. Set the multi-meter to read DC volts.
6. Place the probes on the SC and GND test points located on the bottom-right of the MB. Remember to place the black probe on GND. The meter should display a negative value between -0.5V and -2V (there is a wide range because we have not calibrated the ratio yet).

The meter has two sets of pins: two big ones for the meter signal, and two small ones for the LEDs. And on the body of the meter there are "+" and "-" markings.

As with the "IN" switch, pin 1 of the wiring harness is marked on the body. Note that for the first batches of kits, the colors of the wires are different from those shown in the photo.

Solder a jumper wire between the Big + and Little - pins. Then, solder the pin 1 wire of the harness to Little +.

Crimp and solder the terminals to the remaining two wires of the harness. Then insert the pin 2 terminal onto the Big + pin, and the pin 3 terminal onto the Big - pin of the meter.

The meter and wiring harness should now be wired as shown below:

• CON1 pin 1: Little +
• CON1 pin 2: Big +
• CON1 pin 3: Big -
• Jumper Big + -> Little -

After double checking, connect the wiring harness to CON1.

Quick-connect terminal (x2)

1. As you did for the last test connect your interface to both inputs but leave the outputs disconnected.
2. Send the same test signal from REW as before (60Hz sine wave, +4dBu).
3. Engage the compressor with the IN button.
4. Turn the THRESH knob until you see compression on the meter. If the meter shows gain reduction, you can move on.
5. Disconnect the CBs, IN switch, and meter from the MB.

Trim the leads of the transformer down to about 1.5" (38mm). Be generous! You can always cut them shorter, but you can't make them longer after you've cut.

Then strip off about 1/8" (3mm) of the insulation and tin the leads by applying a bit of solder.

Place the wires through their respective holes and solder. The GRY and VIO holes are for using different transformers and should remain empty.

To avoid damaging the connectors during this section, disconnect the CBs, meter, and IN switch from the MB. Remove the washers and nuts from the TRS jacks. Then place the MB in the chassis and fasten it to the standoffs via the short screws for the PCB and the long screws for the transformers.

PCB screw (x6)

Transformer screw (x4)

Screw the XLR jacks to the rear of the case and then put the washers and nuts on the TRS jacks.

XLR screw (x14)

Each rotary switch includes a washer with a tab that sets the furthest position for the switch. These tabs fit in the square holes around the switch shafts. The numbers are before/counter-clockwise from the corresponding holes. Make sure each switch is in the completely counter-clockwise position, then place the tabs in the following holes:

• SW1_CB, ATTACK: 6
• SW2_CB, RATIO: 3
• SW3_CB, RELEASE: 5
• SW5_CB, FILTER: 6
• SW9_CB, DRIVE: 3

Each potentiometer has two nuts: one to go behind the U-bracket and one in front. Thread the inside nuts all the way onto the pots, then fasten the CBs to the U-bracket via the nuts and washers of the rotary switches. Then adjust the inside nuts of the pots until they are flush with the back of the U-bracket. Finally, attach the lock washers and nuts on the front size of the bracket.

Screw the U-bracket to the bottom of the chassis then connect the cables to the MB.

U-bracket screw (x3)

Fasten the front panel to the chassis. Then place the meter and IN switch through the front panel and connect them to the MB.

Front panel screw (x4)

Press the knobs onto the potentiometers and rotary switches.

The audio VCAs must be manually trimmed for the lowest distortion.

1. Connect inputs and outputs to the L channel. The compressor should be disengaged.
2. Send a 1kHz, +4dBu test signal.
3. Open the RTA window, click "Show Distortion" and the Record button
4. Trim VR2 so that THD is as low as possible. The absolute number is not important and will depend on your setup and the channels may not match exactly. As long as each channel measures below 0.1% THD there is no cause for concern.
5. Repeat for the R channel.

This is where we will truly make your G Bus as authentic as possible by dialing in the ratios to match the original console. The actual ratios after calibration will be approximately 2.3:1, 3.5:1, and 5.8:1. Those may seem too different from what's printed on the front panel, but they are the actual numbers from a vintage console.

1. Connect inputs and outputs to the L channel. Send a 1kHz, -20dBFS test signal.
2. Engage the compressor, and set RATIO to the middle position (4:1).
3. Turn THRESHOLD until the IN meter in REW reads -30dBFS.
4. Change the test signal level to -10dBFS.
5. Trim VR4 in the RATIO section until In reads -27.15dBFS.
6. You do not need to repeat this step for the R channel.

Note: If you cannot get the level down to -30dBFS in step 3 you can simply increase the level by 10dB. So for step 3 you would send a -10dBFS signal and compress down to -20bFS. For steps 4 and 5 you would send a -0.1dBFS signal (or as close as you can get to 0dBFS) and trim VR4 for -17.15dBFS.

Finally, we will calibrate the meter so it is precise at 8dB gain reduction. After calibration the meter should be accurate up to 12dB, but it is normal for it to drift off at higher gain reduction levels.

1. Send a 1kHz, -10dBFS test signal.
2. Open the Levels window and turn THRESH until "In" is 8dB lower than "Out."
3. Trim VR3 until the meter shows 8dB gain reduction.

Place the lid on the case with the countersunk side facing up. Screw in the three screws that attach to the U-bracket first, then the rest of the screws.

All good? Congrats on finishing your build! Have a question or problem? Drop us a line.