Erica Synths Mixer II - DIY Build

The Erica Synths Mixer II is part of the DIY series that are now being offered by Synthrotek. Of course, when we heard this, we had to reach out to our friends in the shop to see if we could get irons this kit. A couple of weeks later the kit arrived and we anxious to get it into the shop and in our rack.

So what exactly is a mixer…?

A mixer is literally just that. It mixes whatever you put into it into something with all parts combined. We know how simple that sounds, especially if you think of it like cooking or baking terms. A mixer, mixers the ingredients together to make something else. 

Erica Synths simple describes the Mixer II as a “simple, straight-forward audio mixer” and that the Mixer II is an “essential part of any modular setup.” This is where Erica Synths could not be more correct. A mixer is an essential part of any music recording whether it be via a studio rack, performance rack or recording console (aka. mixer); you need it to mix your ingredients into something else. 

The Build... Quick and Easy!!

The build of the Erica Synths Mixer II is relatively simple and it only consists of a few components, knobs, 3 pots and 5 jacks.  That’s it. If you are new to DIY or thinking about getting into DIY Modular, this module is an excellent choice to start with. Intermediate and advanced builders will find this kit a quick build with little to no hassle. 

Resistors, Diodes and those weird beads…

First off, start by placing the resistors. Their polarity does not matter so don’t worry about the orientation. Just match things up with the provided BOM. After the resistors are mounted, place the diodes. These need to match up to the silk screen or the module will be trash. Lastly, move onto the the big black beads (aka ferrite beads). The ferrite beads are a little larger, but a quick bend at the component mark on the leg and they will fit perfectly into the PCB. 

Once everything has been placed, whip out the old trusty iron and get to soldering. We used a top-down method which made tacking things down quick and easy. After completing your first run on the top of the PCB, flip the board over, cut the legs and touch up any points that need it. You can now move onto step 2. 

Erica Synths Mixer II - Time Lapse Build

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Caps, IC Socket and the resettable fuses…

Polarity does not matter with any of these components except you need to be aware of the orientation of the IC socket. If this one is mounted incorrectly, it could fry your board or IC. An easy to mount the socket is to place a small dab of solder into one of holes on the PCB. Gently, push on the IC socket as you apply heat to the underside of the PCB and the socket will just “clip “ into place. Once this has been completed flip the board and complete the soldering on the socket. 

After placing the caps and the fuses, flip the board and solder the legs. It helps here to bend one or both legs on the caps to help keep them in place when you flip the board. This is due to the different sized components on the top of the PCB. Upon completing this part of the Erica Synths Mixer II, it is time to move onto the electro caps and power header. 

Power that baby!…

The next stage in the build process is the power header and the electrolytic caps. We started with the power header and to be honest we were unclear about its orientation when we first looked at the BOM and Assembly Guide… it just wasn’t clear. We utilized the “Component Placement Guide” provided by Erica Synths to help us out. If you look in the photo to the below, the “notch” in the header faces down towards where the jacks would be. If you mess this part up, you will have a paperweight on your hands… so pay attention here. 

Treat the mounting of the power header like the IC socket by placing a small dab of solder over one whole and then heating up the solder from the other side while gently pushing the header into place. Once it snaps into place, finish up tacking down the rest of the header to call it done. 

Erica Synths Mixer II - The Electro Caps…

The electrolytic caps are next on the list and it is VERY IMPORTANT that you mount them correctly. Each one has a long leg and a short leg. The short leg is the same side as the “white” stripe on the cap. Make sure that you mount these with the white stripe facing out (lined up with the white silk screen line. Flip over the board and tack them down. Time to move on.

Wrapping it all up…

The jacks and pots will be placed on the opposite side of the board. Do not solder anything down after placing the parts though. Wait until you have the panel hand mounted so that everything lines up where it needs to be. You can tack down the long pin on the jacks to just hold them in place and still allow movement. We do this all the time. 

Place the panel and hand tighten the nuts on the jacks and pots. Once its all lined up, flip the panel/PCB over and start to solder all the parts that need it. Be careful here… as it can get really tight in some places when you are soldering. You do not want to leave the heat pressed up against other components for very long at all (seconds). After you complete all of the soldering of the jacks and pots, it is time to tighten the nuts on the front of the panel and move onto the knobs and testing. 

Knob, knobbin…

Knobs are funny. People have certain likes and dislikes when it comes to knobs. The knobs on the Erica Synths Mixer II are actually perfect size and height. Just use the little set screw to tighten them onto the pots, making sure that they line up accordingly with the pot turned all the way clockwise. When you finish this, place your IC into the IC socket and head over to your test rack. 

Calibration … nah son!

Mixer’s are easy to test and calibrate. To test our mixer module, we simply plugged it into our Synthrotek TST module and made sure everything fired up correctly. No smoke, so we were good to go.

After testing, one usually calibrates a module, but with the Erica Synths Mixer II, you don’t have to calibrate anything. Just plug in your inputs and pipe your outputs to your DAW or computer and you are good to go. 

Erica Synths Mixer II - Completed Module

Features and Specifications


  • Three AC coupled audio inputs
  • Two outputs
  • Skiff-friendly design


  • Width: 6HP
  • Depth: 30mm
  • Current draw:
    • +12V: 4mA
    • -12V: 4mA
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Erica Synths Mixer II - Purchasing Options

Synthrotek offers a several options when it comes to purchasing the Erica Synths Mixer II module. Their prices are excellent and the quality of this build is way worth it! If you are interested in buying the kit, the assembled module or just the PCB/Panel/IC, click on the images below and you will be redirected to their site to purchase! Make sure and tell the gang at SR that we sent you!

Assembled Module
Panel/PCB Combo

Erica Synths Mixer II - Documentation

Our Final Thoughts . . .

We have multiple mixer modules in various cases. We were interested in this one because 1, it was only our second Erica Synth module and 2, it was DIY. The Erica Synths Mixer II is a quick and easy build for intermediate and advanced builders. If you are new to the DIY world of modular, take your time with this one… there are some tight spaces on the PCB. 

The dark black panel and the knobs bring together the aesthetics of the module and the low price makes this mixer hard to pass up. Whether you are recording, performing or just jamming into your DAW, the Erica Synths Mixer II can get the job done!

Comments or Suggestions?

If you have questions about the build process or suggestions/feedback about this article, feel free to let us know by contacting us  We look forward to hearing from you!

Until the next build … 

~ f i N

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