Passive Multiples - DIY Quick Builds
In the world of modular synthesizers, multiples are a staple in any system. While there are many different manufacturers of multiples, their primary function remains about the same. They are used to duplicate a signal to send it somewhere else in your system. The most common type of multiple is known as the passive multiple, or quick multiple being that it does not require power to function. They are basically a bunch of jacks wired together with no circuitry between them. You plug in your input in one jack and it sends to a series of outputs. It is that simple.
Passive multiples not only come in a modular form (1U, 3U, 5U etc) but they come in other shapes and sizes. Jumper cables (or stacking cables), passive stars or trees are also other types of multiples. One of our featured previous builds was the Catwalk Series from Waveform Magazine. This was a very unique take on the passive mult being that it did not take up any space in our rack. It simply mounted on top of any other module to act as a quick bridging module. It is definitely one of our favorite passives to utilize. Basically, a passive multiple can be anything that can output to more than 1 output jack that takes no power.
~ Pure simplicity at its finest ~
Now, with all this talk of passive mults, there are some downsides to using them. Since they are not powered, unwarranted results could occur with internal circuitry or with throughput to other modules. Some modules have circuitry that is internally buffered and if you patch to one or more outputs, the output voltage could ultimately change causing a drop in signal or wave shape…. but we aren’t going to get too much into that.
In our quest to bring modular DIY builds to you, our audience, we decided to take on a couple builds of passive modules. These modules are a quick and easy build with 3 main parts. A panel, a PCB and a set of jacks. Sometimes you will even find passives without a PCB being that they can just be directly soldered together.
One might find 1×8, 1×9, 2×3 passives, whereas the first digit represents the number of inputs and the latter represents the number of outputs. Some manufacturers also give you the option to decide which input/output numbers you want by simply soldering a jumper wire or two.
NCMC LODI and SR Passive Mult - Time Lapse Builds
Now, one may ask, besides the output configuration option, what is the difference between the modules? The answer is not much except for HP (rack space) and jack nut types that we used. The Passive Mult by Synthrotek uses standard hex nuts (our preferred) and on our Lodi Mult we used Thonk type jacks with knurled nuts (not our fave). The Synthrotek Passive Multiple is 2HP whereas the North Coast Modular Collective Lodi mult is 3HP. Not a lot of difference there, but if you are struggling for room in your case, you will want to pick up the one with a smaller footprint. Let’s get on with the build shall we?
North Coast Modular Collective - Lodi Mult
As you can see from the time lapse video, we started with the Lodi mult. It’s white panel and and green PCB arrived in about a weeks time of purchasing on the North Coast Modular Collective Etsy page and set us back about 16$ for the panel/pcb combo. Since we had THONK jacks sitting around, we utilized those (ugh). Begin by lining up the jacks onto the PCB and solder the ground pin on the jack moving from one jack to another. Use top down soldering to help with stabilization.
Once you get all of the ground pins soldered to the PCB, place the panel on top of the jacks making sure to line everything up accordingly. Next, hand screw down the nuts on the jacks so that the panel stays in place when you flip the module over. Finally, go ahead and solder the rest of the jack pins on the back of the PCB and you are done. A quick tighten of the nuts on the jacks and you have just built your first passive.
Synthrotek - Passive Mult
The Synthrotek Passive Mult is next. As another relatively inexpensive module, the footprint of this one is slightly smaller which makes for a more cramped soldering surface area. The workaround for this is to just take one jack at a time. Starting with the top jack and working down, place the jack, solder the ground pin and move onto the next one.
After you complete all of the ground pins, place the panel over the jacks and hand tighten the nuts just as you did on the Lodi. Flip the module over and solder the rest of the pins on the jacks. We utilized our Synth DIY tool set to tighten down the nuts and wrap up the build. Pat yourself on the back, another passive mult build is complete.
Wrapping it all up...
Since there is no circuitry in the modules, you can take it over to your system and put it to work. We actually use our passive multiples to test our modular LED plugs that we manufacture in our shop.
Being that we can pop a SINE wave into the input and then either output to 7-8 other outs, it lets us see that our plugs are ready for shipment. Call it a simple tool for quality control… (ie. another useful purpose).
Synthrotek Passive Mult - Purchasing Options & Quick Links
Synthrotek has a couple different options when it comes to purchasing the Passive Mult module. We wanted to keep it simple by just placing images of the options and linking out to the direct purchase. The prices are excellent and the quality of this build is way worth it! Head on over to SR and tell them we sent ya!
North Coast Modular Collective - Purchasing Options & Quick Links
As it states on their main site, “North Coast Modular Collective exists in order to expand the skill, knowledge, and accessibility of the electronic music community through the development of music, instruments, and community resources.”
They have several eurorack modules available to purchase over on their ETSY page which you can find the link below. Tell them that we sent ya while you are there!
Our Final Thoughts . . .
In the end, the passive mults come in a lot of different shapes and sizes. They are a pinnacle utility tool in ones modular systems. When we asked one of our friend hhnoi what his favorite module to use was, he simply responded with “a mult”. The easiest way to think of a passive mult, is to think of it as a patch bay of the modular system. With so many configurable and unlimited patching options, it’s easy to see why you will have more than one in your rack.
Their low cost and lack of power make them a must have for any artist. The Lodi Mult and the Passive Mult from Synthrotek are excellent choices for DIY kits as you can see above. They are quick and easy builds with little to no extra skills needed to build. We highly recommend picking up one if not both modules. (we have 2 of each and intend on using every last jack when we need it).
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 …