Synthrotek Power Pak, Adapt 1/4 and Stereo Buffered Mult - DIY Builds

In the vast world of modular synthesis, one has to have many tools at their disposal to get the sounds they desire. Synthrotek has recently released a set of modular tools (modules) that have small footprint in ones case, but provide a big impact to some common simple issues. 

We picked up the Stereo Buffered Mult, the Power Pak as well as the Adapt 1/4 (Quarter); an adapter module that allows you to mix and match cable types/sizes. If you would like to jump to a particular build, use the quick links to the right.

For the most part, these builds are quick and any novice builder could tackle these as their first DIY projects. The panels are the standard black with a green PCB and of course the gang over at Synthrotek provide a printed BOM with each kit. Relatively inexpensive, you can purchase them below or directly from Synthrotek. 

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Module 1: The Stereo Buffered Mult or S. MULT

Everyone needs multiples in modular synthesis. The S.MULT is a stereo buffered multiple that has two channels. How does it work you ask? A signal plugged into Input 1 will be available from all 6 outputs. Break the chain by adding a second signal into input 2; signal 1 comes out 3 outputs and signal 2 is available at the remaining 3. 

If you are concerned about mono signals, no worries! The Synthrotek S. MULT can still be used for mono signals! With a mono input you can use both mono and stereo outputs at the same time, but will only get a signal on the left of the stereo outputs.

You can also plug mono or stereo patch cables into the outputs and they won’t interfere with each other; the mono output will be the left of the input. Pretty cool eh?

The Build (Intermediate)

This is a quick build with a few diodes, 2 values of resistors, some ICs/sockets, power header, cable and some jacks. Panel and PCB are also included in the kit or you can just buy them separately and outsource the parts on your own. 

Upon starting the build, place the diodes and note their polarity. The black stripe needs to match the silk screen on the PCB to ensure correct functionality. With resistors, polarity doesn’t matter so you can just pop them in and tack them down.

After these two components are done, place the IC sockets but not the IC’s. Flip the board over and solder the sockets into place. While you are here, tack down the power header and call that done too. Lastly, we will mount the input/output jacks and complete the module. 

Synthrotek Stereo Buffered Mult - Time Lapse Build

Play Video

Stereo Buffered Mult - Build Gallery

Completing the Modular Build

Carefully place the jacks onto the PCB and then place the panel over the jacks to hold them all in place. Hand tighten the nuts on the jacks and then flip the board over and tack everything down.

Once you have completed this part of the build, you can insert the IC’s making sure that the legs are straight and not bent and you match the notch with the PCB silkscreen. Pat yourself on the back, you have completed this module! 

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Module 2: The Quarter/Adapt 1/4 (Beginner Build)

The Synthrotek Quarter or Adapt 1/4 is exactly what you think it is. It converts 3.5mm jacks to 1/4 (quarter) inch jacks. You can choose between 3.5mm, banana or even RCA L/R input options, while all output jacks are 1/4 inch.

Ours is configured as 3.5mm stereo to 1/4 stereo and our left and right channels are the same. Since we don’t use RCAs or bananas, this made the most sense to us. Let’s jump into the build… 

Synthrotek Adapt 1/4 (Quarter) - Time Lapse Build

Adapt 1/4 (Quarter) Build Gallery

The Build and Completing the Module

Quite literally, this is a simple build. Mount the 3x 1/4 inch jacks to the PCB as well as your input jacks (ours were 3.5mm). Next place the panel on the jacks and make sure everything is lined up. Hand tighten the nuts on the jacks and flip the board over to solder everything into place. You have completed the Adapt 1/4 (or Quarter) by Synthrotek. 

Note: If you are using banana jacks or RCAs, please make sure to refer to the BOM that is included in the packaging to make sure you hook everything up correctly.

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Module 3: The Power Pak (Advanced Build)

The Synthrotek Power Pak is probably our favorite module in this write up, due to its versatility and ability to think outside the eurorack box.

As with most builds, start with the diodes ensuring that they line up with the silkscreen. This is due to the fact that they are polarized and they need to be facing a certain direction when placed. 

White Synthrotek Logo

Regulators…. mount up…

The 9v regulator and the 2 pin header are next. If your case already has a 5v rail installed, or if you purchased the version of the kit WITHOUT the 5v regulator, you DO NOT need to populate the 2 Pin header.  We went ahead and did placed it and left the jumper off since we have 5v rails in our case.

When you install the 9v regulator, notice that it has a dot on the side to mark pin 1. Make sure when populating it that you match that dot to the dot on the PCB or things could go really south. After everything is in its place, flip the board over and tack everything down, trimming the leads afterwards. 

Resistors and Fuses

Next up are resistors. Since these are non-polarized, you can mount them in any orientation you would like. Make sure you are mounting them on the backside of the PCB and then after soldering the leads, trim them off like other components.

Flip the board over and place the 3 resistors on the front mounted vertically and trim their leads as well. 

As for the fuses, there are only a couple and they are like the resistors in that they are non-polarized. You can place them in their homes, tack them down and trim the leads. 

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Synthrotek Power Pak - Time Lapse Build

5v Regulators

Similar to the 2 pin header, if you already have 5v in your case, or you purchased the version of the kit without the 5v regulator, you can skip this step The 5v regulator is polarized, so when you are populating it, make sure to line up the vertical pcb part of it with the line on the PCB, and the side with the large black box facing towards the fuse. Once you have it in there, carefully flip your project over and solder it in place.

Front Panel Placement and LEDs

Due to the size of this design, we will need to install the front panel temporarily to solder the LEDs in place. Go ahead and populate the 4 DC jacks, and the three LEDs, making sure to follow the BOM. Since the LEDs are polarized, care needs to be taken to ensure they are oriented properly.

When populating them, insert the longer leg (anode) of the LED through the hole closer to the little ‘+’ symbol on the PCB. Once everything is in place, set the front panel down over the top, and tighten the dc jack nuts so that it holds the front panel in place.

When you flip the project over to solder everything, make sure that the LEDs are pushed up against the back side of the front panel fully, and that they are all even. Also double check to make sure all the DC jacks are fully seated and the two boards are parallel. When everything looks good, solder everything in place and clip the leads. 

Power Pak Build Gallery

IMPORTANT: Because the LEDs solder points are behind the power jacks (once installed) you will need to clip the leads as close to the PCB as possible. It is recommended to immediately reflow the solder points for the LEDs, just to ensure there aren’t any cold solder joints. You will not be able to get to them once the project is completed. 

Power Headers

The Synthrotek Power Pak also has 2 power headers that will be used in tandem when powering the module. This is to ensure that you have enough power for distribution. Match the notches on the header to the silkscreen and flip the board over to solder everything into place.  Make sure you try to get them as flat as possible but don’t fret if they aren’t perfect due to the LED solder points. 

Wrapping it all up…

Next up are the USB jacks on the front. Insert them into the front panel first, and then insert the front panel assembly into the PCB. You will need to slightly bend the two case pins (the bent ones) on the USB jacks to get them through the front panel, and then bend them back out (once in) so that they fit into the PCB. Take your time with this as it can get very tricky to line things up. 

Once you have everything fully seated, go ahead and put the nuts back on the DC jacks, and make sure everything is nice and flat. When it looks good, flip the project over and solder the USB jacks into place. You have now completed the Power Pak by Synthrotek. 

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Where do you get one of these badass modules?

Synthrotek has a couple different options when it comes to purchasing the the Power Pak, Adapt and the Stereo Buffered Mult modules. The prices are excellent and the quality of this build is way worth it!

If you are interested in buying the kits or the assembled modules, 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!

Purchasing Links

Our Final Thoughts

After completing these kits, it is easy to tell why they are so important to ones system. The Adapt 1/4 lets the user customize their output, the Power Pak allows the ability to hook up different types of devices and the S. Mult is just that… a stereo mult.

All of these modules serve a purpose and it is very apparent when they are in the rack and being used. Build levels range for these modules and caution should be taken when building/testing external devices with the Power Pak. The modules are aesthetically pleasing and they match their brethren kin produced by Synthrotek.

With all of the different modules out there, it is important to not forget about the basic utility modules. Head on over to Synthrotek and pick them up today!

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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