Synthrotek 1U Stereo Output Mixer - DIY Build

If you are like us and have multiple modular racks in your studio, there comes a time when you end up with a row of 1U. We didn’t have one until we purchased a lunchbox case from the gang at Synthrotek.

With 44hp to spare in our 1U slots, we opted for 2 modules that will fill up the space completely and be very useful. The first module we bought was the Synthrotek 1U Stereo Output Mixer.

This module not only made sense, it was to be our go to for all audio leaving the case.

Considering we have built many modules prior, we didn’t expect to have any issues building the 1U module (PulpLogic format), so let’s get on with it. 


Start with the  diodes and mount them according to the PCB silkscreen. Solder them into place and then clip the leads. Diodes are polarized components so you must match the black stripe on your diodes with the white stripe on the PCB silkscreen or the module will not work. 

IC Socket

Place the IC Socket by aligning the notch with the notch graphic on the PCB Silk Screen.  Turn over on a flat surface and solder into place.

Synthrotek XFD - Time Lapse Build


The resistors have to be installed in a standing up position. Simply bend one leg over and place the resistor according to the BOM. Since these are non-polarized, you don’t have to worry about which leg you bent and which leg you didn’t.

Just make sure you mount them in the correct position. We like to go through and solder the bent leg so that when we turn the module over, we only have one leg to complete and the component stays in place. When you are done with these (there are quite a few), it’s time for the caps. 


Tack down the non-polarized caps by bending the legs to keep them in place when you solder. Next, make sure you orient the electrolytic capacitors in correctly.  The longer lead needs to be inserted into the hole that has the “+” marking near it.  Turn over to solder and clip leads. You are done with the caps and its time to move on. 

Power Header and Pin Headers

Next add the 10-Pin Eurorack power connector in place by matching the key notch with the key indicator on the PCB silk screen. Turn over and solder on a flat surface. Place the 3 PIN jumper header pins in place.  Turn over on a flat surface and solder into place.

Synthrotek 1U Stereo Output Mixer - Build Gallery

Jacks and Pots

Time to flip the module over and place the jacks and pots into their spots. Do not solder anything yet, as we have a bit of wiring to do. Grab the stereo jack (1/4”) and wire it according to the data sheet.

Mount this jack to the backside of the panel of the module. It will be the only thing there until you flip over the panel and gently place it over the other jacks and pots.

Use a few nuts and hand tighten them down over a few of the jacks or pots. This will hold everything into place as you flip the module back over and tack everything down. 

IC and Knobs

Remove the panel nuts you previously placed and grab the IC. Make sure the legs are bent 90 degrees and mount the IC according to the layout on the PCB. (There should be a small indicator at one end of the IC that will match up). After this is complete, place the panel back on the module and tighten it down.

Place the knobs and then pat yourself on the back, you just completed the build. 

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Where do you get all of these wonderful toys?

Synthrotek has a couple different options when it comes to purchasing the 1U Stereo Output Mixer module. The prices is excellent and the quality of this build is way worth it!

If you are interested in buying the kit or the assembled module, click on the links below and you will be redirected to their site to purchase! Make sure and tell the gang at SR that we sent you!

Main Control Board Connection

Connect the main and control boards together by aligning the header pins and sockets and then screw in the screw into the standoff.

Our Final Thoughts

You can’t go wrong with the Synthrotek 1U Stereo Output Mixer in that it does its job. It mixes audio and even adds a little gain to the output per the user preference. The build was a basic to intermediate build and we would suggest having a few other builds under your belt prior to taking this one on. This is just due to the fact that there is some tight soldering spots and you need to have a gentle hand when doing so.

We can sum it by saying that this module is exactly what we needed for our lunchbox case and we are glad we picked one up. 

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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