Gakken Theremin Kit Hack




About: My name is Randy and I am a Community Manager in these here parts. In a previous life I had founded and run the Instructables Design Studio (RIP) @ Autodesk's Pier 9 Technology Center. I'm also the author ...

Here are instructions to do some basic hacks to the theremin kit that you can buy from Make. True, there are already directions to do both of these things in the accompanying magazine, but what sets this how-to apart is that it is in English. If like me you can't read Japanese and unlike me, you couldn't figure out what to do from the pictures alone, this should help.

Basically, what I am doing is adding an audio out jack and also a bigger, sturdier telescoping antenna. This is a great improvement on the original.

Step 1: Go Get Stuff

You will need:
Gakken Theremin Kit (from Make)
A power drill
A mini screwdriver set
A mono jack with switch
Something with a telescoping antenna
A solder setup
Some extra wire
Assorted hardware

Step 2: Make the Kit

Before you can hack the kit, make it! See if it works. See how it works. Determine if you really want to make it better.

Alright, let's now assume that you do.

Step 3: Open It Back Up

Alright, lets make this thing better!

First thing is first, we need to open that theremin back up.

Remove the screw in the bottom and take the casing apart.

Step 4: Drill and Install

Drill a 1/4" hole in the back of the theremin just to the right of the speaker. This will be for mounting your audio out jack. I found holding the panel in place where it should be helped me to drill it on target. You should not do this. Always clamp things down and be safe when working with power tools.

Once you have your hole drilled, mount and fasten the jack in place.

Step 5: Wire It Up

Now is time to wire up the jack. This may require adding in a little extra wire.

First wire SP- (the wire on the right) to both the audio signal tab on the jack and the minus tab on the speaker (where it was just connected). Or, to put another way, wire the audio signal tab on the jack to SP- and the minus tab on the speaker.

Then wire the SP+ wire (the wire on the left) to the tab that connects to the big rounded metal bit on the back of the jack. Wire the + terminal on the speaker to the only other free jack (the tab that connects to the the little metal switch on the inside of the jack). This will turn off the speaker (break the connection) when someone plugs in an audio cable.

Step 6: Get a New Antenna

Take your "something with a telescoping antenna" and remove the telescoping antenna.

If it does not have a wire and piece of hardware on the end that will clamp nicely under a screw, you may want to attach one.

Step 7: Attach the Antenna to the Case

Insert the antenna into the case and secure it in place.

I drilled a small hole in the side and held it in place with a spacer and a machine screw.

Step 8: Wire the Antenna

Detach the old antenna by removing the screw and clamp in the new antenna in its place.

Step 9: Close the Case

Hot glue any exposed wires in place so that they won't touch anything and short out (and/or insulate them).

Also, chop off any part of the plastic inside the case that may interfere with it closing.

Once you have done all of this, close the case back up and reassemble it by inserting the single screw back into the bottom, putting in some batteries and closing it back up.

Participated in the
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    15 Discussions


    3 years ago

    What's the level coming out from the lead? I suppose it's speaker level and perhaps it is too high to plug it into a guitar effect pedal? Thanks!

    2 replies

    Reply 3 years ago

    I don't know. A roommate broke it years ago. It is long gone.

    You can add a potentiometer before the output jack as a volume knob. Connect the middle pin of the pot to the signal connection on the jack. Connect one of the outer pins to ground on the circuit board and the other pin to the audio signal from the circuit board.


    Reply 3 years ago

    Thanks! I've connected it with a guitar amp, and the level is too high even if I turn the input knob all the way down. I'll try to add two resisters as voltage divider.


    Reply 10 years ago on Introduction

    yeah, but i really like the sound cancelling headphones you used, where did you buy the sound canceling headphones ( without the speakers inside) wich store? or the web? thanks


    10 years ago on Introduction

    If you find the audio-amplifier circiut (should be a simple op-amp) you might be able to tap into the signal and get line-out voltages from this.

    2 replies

    Reply 10 years ago on Introduction

    It's just a 386. I considered doing that, but decided to just go along with illustration in the accompanying magazine and see how that goes.


    Reply 10 years ago on Introduction

    Always good to follow the instructions first, and then do your own after. Give you a better idea on what's going on.


    10 years ago on Introduction

    a pox on digital theremins! it's not a real theremin (though...that's obvious with this one)...the sound is never as good as an analog one

    theremaniacs make a nice analog single antenna model that's pretty cheap (relatively)...i got one of these kits for my dad and made my own case/mount/whatever for it out of a cigar box and a little bust of chairman mao...sounds great!


    10 years ago on Introduction

    Nice one, very detailed. One thing might be important, the output signal from the jack is very strong, its a good idea to use headphones with volume control like i see in the picture above. I can use Ipod speakers on it without turning them on. I didn't dare to hook it up to an amp, i think it might blow it. I'll build a mixer first.


    10 years ago on Introduction

    Nice! I think you did a great job modifying it. I have always wanted a theremin. Goes to waste money on one..