The Nerve Center Eurorack Module is a 10HP, easy to build and adaptable mixer able to meet any of your mixing needs. It can be a 4:1 mono mixer, two 2:1 stereo mixers, individual attenuators, or any combination of these. It will happily mix audio, CV signals, or both!
The kit contains everything you need to build the Nerve Center. Pictured below are the panel, the “fader board” on which most of the bigger components will sit, and the “backpack board” which will be populated with the smaller components.
The BOM (Bill of Materials) is a spreadsheet shown below which is a list of all the components in the kit and includes the place holder name of the PCB's included in the kit.
Beginner Tip: As you finish soldering components, strike the spreadsheet entry with a marker or pen so that you know what part of the build has been completed.
Now let's begin our build. We'll start with the backpack board (the little one) by placing resistors and diodes. It doesn't matter which way the resistors go in, but beware, diodes have polarity. Make sure to align the striped end of the diode with the striped side of the diode footprint on the PCB.
Now we'll do the resistors, which are all of the same value of 10k for the backpack board.
Now that are resistors and diodes are populated, let's solder those suckas!
Beginner Tip: It helps if you fold the legs of the components away from each other to hold the component in place.
Once soldered, we can clip away all those nasty legs. Trim away the leg so the volcano shape of the solder joint remains. Don't go much lower than that, and no need to leave any of the leg poking out the top or our solder mountain.
Next we'll do our op-amps and capacitors. The op-amps must be placed so that the notched end of the op-amp matches the notch symbol on the footprint. After you've placed them, double-check you have the correct orienation!!! If you put them in backwards, you will have a very hard time fixing it, and your mother will cry. You may have to bend the legs a little for them to fit into their slots. Place the op-amp against a flat surface and push slightly to bend the pins inwards equally. Also, when soldering IC's, it is best so solder only one pin and make sure the IC is flat before soldering the rest.
Electrolytic capacitors (the ones that look like Coke cans) have polarity, so make sure the striped side of the capacitor with the (-) symbol is facing away from the (+) symbol on the PCB. The little yellow ceramic capacitors do not have polarity, and so it doesn't matter which way they are placed.
The orientation of these components is pictured below.
The power header will be placed on the same side on the PCB as the components, and the short pins will go through the holes on the PCB. Again, solder one pin and make sure it is flat before soldering the rest.
We will now solder the male pin headers onto the back of our backpack board as shown below. Again, we want to make sure they lay flat, so solder one pin and check for flatness before soldering the rest.
We're now done with the backpack board. Yay! Onto the fader board.
We will once again start with resistors. All the resistors on this board are 2.2k. Place em', solder em', clip em'!
We will solder the female pin headers to the back of the fader board to accommodate our little backpack board buddy. Again, we really want these to be straight for when we eventually connect the male and female pin headers, so solder one pin and make sure it is straight before soldering the rest.
The next component to place are the switches, and we must be careful to place them correctly. The switches have a small triangle on the shaft of the push button. This small triangle on the switch must align with the triangle symbol in the switch footprint on the PCB.
Onto the jacks! The two jacks facing each other vertically will share a ground hole. We'll stuff our third leg of both jacks through the middle hole between them. Solder those babies and we'll move on.
Onto the final and most exciting component: the faders!! Impossible to mess these up since they only fit into the panel in one orientation. It's a little tricky to get them to lay flat when you flip the board over to solder them in, so I taped them down with masking tape to keep them in place while I solder. Again, solder one pin and check for flatness, reflow that pin with a finger on the part to get it seated perfectly.
Now let's solder in our final components.
The final step: the two boards must be connected via the male and female pin headers, as well as using two screws, a spacer, and a 7mm nylon standoff. Place the small spacer onto the screw, feed the spacer'd screw through the hole at the top of the fader board, and thread the screw through the standoff. Align the male and female pin headers and socket the backback board fully. Stick a screw through the backpack board and tighten it to the standoff. Do not overtighten, these fasteners are only here to keep the backpack from unclipping and do not need to be overly tight.
I know at this point you'll want to throw on the panel and see how pretty your new module is, but slow down a minute. Patience. You may want to test it before going through all the work of putting on the nuts.
Apply eurorack power and press the 4 buttons - you should see the LEDs on the faders light up with each button press. Feed signals into each of the 4 inputs and make sure you hear that signal on the outputs. If you're having issues, narrow down which channel isn't working, to give you a hint as to where to troubleshoot. If you're not getting any lights at all, check power cable orientation, and check your diode orientation.
We now know the module works, and so we'll attach the panel to the boards using a screw on either end of the metal standoffs provided which will sit between the fader board and the panel. Don't forget to put the button tops onto your switches before mounting the panel. They only fit onto the switch in one direction, no need to force anything.
Damn, that's a beautiful mixer you've got there. Happy mixing!