Build Guide - 004 - Mixer

Here’s the guide to assembling the Mixer kit! The kit includes the following:

In addition to the contents of the kit, you will also need:

  • Soldering iron and supplies
  • Flush cutters
  • [Optional] Pliers for tightening jack nuts

We’ll start with the PCB and the contents of bag A.

Start with the two black diodes. Look for D1 and D2 on the PCB, near the power connector footprint.

Insert the leads of the diodes into their respective holes, making sure that the stripe on the diode is facing the same direction as the stripe on the PCB. Diodes are polairzed parts, meaning they must be installed in a certain direction.

You can bend the leads back behind the board to make sure they stay put, like this:

Here they are inserted into the PCB. Note the directions of the stripes, highlighted in red:

As you work through this guide, you can solder the parts one at a time, or add multiple and solder them all in one go. To keep things clean, I’ll be soldering and trimming the parts at each step.

Once you’ve soldered the leads, use a pair of flush cutters to snip off the leads, close to the PCB, but with enough material left to ensure a solid connection.

After you’ve installed the diodes, next up are the electrolytic capacitors, for C3 and C4 on the PCB.

Like the diodes, these are polarized parts. There’s a white stripe on one side of the cap denoting the negative side, pictured here:

Make sure the stripe is facing the same direction as the white filled portion of the footprint on the PCB. There’s also a small + sign on the opposite side of the footprint, denoting the positive end.

After installing them, the board should look like this:

Next up are the ceramic capacitors, for C5 and C8 on the PCB.

Unlike the electrolytics, these caps are non-polarized, meaning it doesn’t matter which way you install them.

The last parts from bag A are two 1K resistors. They’ll be installed at R6 and R8 on the PCB.

Resistors are also non-polarized.

Here’s what the board should look like after all of the parts from bag A are installed:

Now it’s time for bag B!

First we’ve got 6 more resistors, all 50K this time. (Okay actually they’re 49.9K because they were cheaper but bear with me here).

These go in all the remaining resistor spots on the PCB: R1, R2, R3, R4, R5 and R7.

Note that R1 and R2 have more compact footprints on the PCB. They should be installed standing up like so:

Here they are installed on the board.

Next up are some more ceramic caps. These are for all of the remaining capacitor spots on the PCB: C1, C2, C6, and C7.

And that’s it for bag B. Here’s what the board should look like:

Now it’s time for the last bag, bag C:

We’ll start with the eurorack power connector.

Make sure to install it with the notch facing towards the text on the PCB, as shown below.

If you’re having trouble getting this part to stay in place, or any other parts during this guide, you can temporarily secure them in place with a bit of masking tape.

Next up is the 14-pin DIP socket, which is installed on the opposite end of the PCB. It doesn’t really make any functional difference, but you should align the notch at the end of the socket with the footprint on the PCB.

Now for the IC itself. Make sure notch on the end of the IC aligns with the footprint on the PCB, which should also line up with the notch in the IC socket.

Carefully insert the IC into the socket. You’ll likely have to bend the pins inward a bit to make it fit. For this, I suggest holding the IC by the ends of the body and gently press the pins down onto your work surface to bend them inward slightly.

Now for the jacks. Start by unscrewing the nuts from each of them.

Note: When making this guide, I installed the pots before the jacks, but it would be easier to install the jacks first, so that’s the order this guide will follow. Just ignore the pots in the following pictures.

Now install the jacks like this. Make sure they’re installed on the right side of the board! They should be opposite all the parts installed so far. Look for the footprints on the PCB.

Here’s what the board looks like with them all installed: (and the pots, oops)

The last parts we need to install are the potentiometers, or “pots”. The 3 pins on the front are the important electrical connections. The tabs on the sides are simply for structural support. You can solder them in place if you want, but it’s not necessary.

Because of the solder bits from the parts on the opposite side of the board, a pot may end up tilted like the one on the left below. Make sure the shaft is pointing straight up before soldering it in place.

In order to solder the pins for the main output pot, you’ll have to maneuver around C7. Just bend it out of the way to solder the pins, then bend it back.

Once you’ve got all of the pots and jacks installed, it’s time for the final assembly! Get out the panel, the knobs, and those nuts you removed before.

Place the panel over the parts on the front of the board. It’s likely that some parts won’t line up perfectly; just bend them gently so that they fit through the panel.

Once the panel is in place, screw the nuts onto the jacks to secure the panel in place.

Finally, press the knobs onto the pots, aligning them with the flat part of the shaft.

And that’s it! Congratulations, you’ve built a mixer module!