Every synth-nerd needs multipliers. If you don't have a multiplier it is like missing salt in your kitchen. It is not that sophisticated, but it is very important.

However, almost every multiplier available is a boring sheet of metal with a couple of jack sockets screwed on it. Since it is a very simple circuit to build, why don't we make it a bit more interesting?

For this reason I created the "Human Multiplier". Its shells are parts of the human body that we could also use as natural jack sockets, but unluckily they don't work.

The amount of available inputs/outputs can vary, and based on that also the part of the body will change.

Step 1: What Is a Multiplier?

A signal multiplier is a circuit that takes one signal as an input and replicates it in many outputs. In this case it is a passive one, which means that it doesn't need a power supply.

It's basically the copy and paste tool for audio signal, and works in the same way as the audio splitters that allow to connect two or more earplugs to the same iPod for more people to listen to the same music.

If used with analog synthesizers, it takes one voltage and copies it many times.

The circuit is very simple, and consists of a certain number of 3.5mm jack sockets connected together in line. It usually comes in the Eurorack format, which is a standard sized plate that can be screwed on a bigger case with all the other modules.

Step 2: First Designs

As a starting point, since I wanted this product to be 3d printed, I kept the design as simple as possible.

I designed a simple profile and extruded it, resulting in very simple shapes. This way, 3d printing these models wouldn't take an excessive amount of time, and could be achieved without supports.

After some testing I found out that the perfect dimension for the holes was 6mm, so no further drilling/finishing is needed to screw the jack sockets in them.

I designed both a vertical version and a horizontal one. The former could stand on the table or on top of the synth, the latter could fit under the synth structure and kept in place there.

Also, in the horizontal version I added secondary functions, such as trays to place things on top of them.

Step 3: 3D Printed Prototypes and Circuit Test

After designing the first two versions and understanding the correct dimensions I 3D printed some of them to check if everything was correct.

The overall design however didn't turn out as expected, and resulted a bit boring and "flat", which is what I wanted to avoid in the first place.

Regarding the circuit I did a test with a metal sheet as a case. I drilled four 6mm holes in it and screwed the sockets in place.

Then I soldered both sides of the sockets in line with some soldering tin, and it worked just fine.

Step 4: Human Multiplier - Models

After realizing the former designs were not exciting enough, I started again from scratch and I came up with the idea of the human multiplier.

I took as a basis some 3D models of a nose, an ear and a mouth. Then I drew some 6mm holes in them in Rhino, and I edited them so they became an empty shell in the back.

Since it is parts of the human body, it could also be possible to use one's own nose/mouth etc. as a shell, after 3D scanning it and editing the model with a 3D software. However, this implies that you have access to a 3D scanner and some 3D modeling skills.

So I decided to give a basis and some information to begin with, and then if someone wants to use their own human components he/she is free to do so.

Step 5: Human Multiplier - Final Product

Putting such an organic and familiar shape next to these hyper-technical machines definitely catches the eye, and has a quite ironic effect.

I rendered some of the models I created to give an impression of how it would look like.

I would definitely say that it is at least a bit more exciting than having another plain grey metal sheet attached to your synth.

Step 6: Human Multiplier - Website

This is an hypothesis of how the website to sell these products would be.

I decided to keep 3 designs available as a default, and they change based on how many inputs/outputs you want. For example, if you need 1 input and 3 outputs you will get the nose, whereas if you just need 1 input and 2 outputs you will get the ear.

This way the range of objects could be potentially expanded with many other designs, that all depend on the number of outputs needed.

Additionally, another feature could be to have the option to upload your own body's 3D scan and create one on your own.