What is Theremax?

Theremax is an entirely new and unique way to interact with a modular synthesizer. Theremax is a three dimensional control interface designed for Eurorack modular system. It senses the location of a hand over its face and outputs a signal proportional to position for each axis: x (left and right), y (up and down), and z (in and out). So, you can control three things at one time, like turning three knobs all at once by moving your hand through the air. The possibilities are truly infinite. You could control the amplitude of a sound with the x axis, the pitch with the y axis, and the modulation of that sound with the z axis. By moving your hand slowly over the surface, you can create subtly evolving, changing and dramatic sounds. With quick movements, you can generate bursts of dynamic audio.

To provide feedback, Theremax has LEDs ringing its active sensing area. These LEDs light up according to the location of your hand. It lights red for the z axis and blue for the x and y axis. As you get closer to the surface, the red LEDs get brighter. As you move closer to a location on the x-y axis, the blue LEDs in that region get brighter and those farther away get dimmer. This makes Theremax visually stunning, brilliant for live play and, excellent for dark spaces.

Theremax can also recognize a number of simple gestures. It recognizes swiping gestures as well as circular motions over its surface. These gestures can be used as trigger outputs and for interacting with the built-in looping feature. Theremax provides a menu system that uses gestures to change the system behavior.

Theremax can record up to 30 seconds of position and gesture data for looping playback. Simply press the large illuminated switch to start the loop and release it to end it. The loop plays back immediately. The loop can be retriggered with swipe gestures or by external signals from a module with trigger outputs. Theremax records as long as the switch is held down, so long rhythmic sequences can be recorded by moving a hand in an out of the active area. The loop switch can also be used as a sample and hold control. When pressed quickly, it freezes the hand position to lock in the output. The loop playback can be sped up or slowed by using circular gestures, clockwise for faster, counter-clockwise for slower. The loop recording can also be triggered externally. One pulse starts the recording and the next pulse ends it. Using external triggers to start and stop recording as well as to synchronize the playback, you can make perfectly synchronized loops.

Design Story

We are all familiar with the vision of the future where we interact with computers by moving naturally in free space. Well, it has arrived. As soon as the gestural technology behind Theremax was announced, I knew that I wanted to explore the possibility of employing it to bring futuristic interaction to the audio hardware world. I began by envisioning a standalone device with a deep feature set, but decided to limit the scope of this design to the core functionality. This allowed me to focus on developing a device using this central technology, leaving the synthesis aspects to proven designs for the time being. I developed a breadboard prototype with development boards and learned the technology.

I’ve been consistently amazed with the accuracy and fluidity of the interaction, losing hours of time, just playing with it, but I decided to add more performance elements, like the looping feature, and a visual element with the LEDs.

These are the killer features that push the design from novel interface to unique sonic tool. For the studio user, Theremax provides an avenue for quickly creating dynamic sounds. For the live performer, Theremax makes tweaking parameters a visual performance event. Turning knobs gets the job done, but moving glowing hands makes it a performance!

How does it work?

Theremax works by generating an electrical field and sensing changes in it causes by the proximity of your hand. Think of it as a smartphone screen with an added dimension of depth four to five inches from the surface. The system uses six electrodes to form the active sensing area. The sensing electrodes are part of the circuit board which lays just behind the piece of acrylic.

Theremax contains an ARM Cortex-M3 microcontroller which decodes the position information and relays the decoded information to digital-to-analog converters which pass through analog circuitry on their way to the outputs. These outputs are scaled linearly corresponding to the sensed hand position with one output for each cartesian coordinate: x, y and z.

Theremax contains thirty-six LEDs which ring the perimeter of the active area to generate an enclosed lighting space. Each LED’s brightness is individually controlled to provide the visual feedback.

Theremax includes the necessary hooks for future directly-connected expansion modules with features like: MIDI, synthesis, filtering, and more. This Theremax module will form the basis for a new line of products. The first planned system expansion module will be MIDI with MIDI-over-USB. It will allow for sending the position, gesture, and gate information over MIDI.

Detailed Features

Resolution: 16 bit Sensing and 16 bit Digital to Analog Conversion

Outputs:

X Position – 0-8VDC corresponding to hand position
Y Position – 0-8VDC corresponding to hand position
Z Position – 0-8VDC corresponding to hand position
Left-Right Swipe Gesture Trigger – 0-5VDC alternates with each gesture
Up-Down Swipe Gesture Trigger – 0-5VDC alternates with each gesture
Gate – 0V when no hand is present, 5VDC when a hand is present

Inputs:

X Gate – 0V turns off X Position
Y Gate – 0V turns off Y Position
Z Gate – 0V turns off Z Position
Loop Sync – Retriggers the loop during playback, start and end loop during record mode

Switch:

Loop switch – High quality feel illuminated switch for controlling the looping feature

Power Supply:

+/-12V, digital voltages internally regulated

Eurorack Width:

36HP Prototype (Production Goal: 32HP)

Feature Requests

The video and pictures show a fully functional proof of concept. But, the final circuit board has yet to be completely laid out. There’s time left for your input and feedback. We can still integrate a whole host of desired features before the design is set.

We’ve already received a number of feasible feature requests that depending on popularity will be implemented in these units:

Loop Storage and Recall
Variable or Different Voltage Output Range (+/-5V, 0-2V, +/-2V)
Quantized or Scaled Output

Schedule

Taking your voice into account, we’ll be working on the boards while the project is running on Kickstarter. We’ll wrap them toward the end of the project. At that time, with the funds from Kickstarter, we’ll order the components and get manufacturing set up and ready to go. Given component lead times and minor delays, we should be able to hit the following schedule:

Kickstarter Project – December 10th,2013 – January 10th,2013
PCB complete and Tested – January 31st
Order Production Components – January 31st
Components Received – April 15th
Production Begins – April 15th
Shipping Begins – April 30th

Where Do the Pledges Go?

The pledges will support final development costs and prototyping, the purchase of components for the units, and the cost of manufacturing.

Kickstarter link to support the project!

Reader Writes: Hi, I wrote some code that easily and cheaply allows audio of any frequency from sub audible to ~8khz to control an LTC1799, or really anything that uses resistance to change a parameter. It’s also able to be controlled by internal 8 bit wavetables. Documentation of that will follow as well. I implemented this with just two chips-an Attiny85 and also an MCP41100 digital pot.

In this configuration, it also doubles as an 8bit DAC. It’s also possible to sequence relays from incoming audio to have tempo controlled sequencing of bends. I’m planning on adding midi code once I start working on the vanilla Arduino port of this.

Here are some examples of this idea in action.

[youtube]http://www.youtube.com/watch?v=B-kf_KLScnQ[/youtube]

[youtube]http://www.youtube.com/watch?v=YP-feTIyPcU[/youtube]

[youtube]http://www.youtube.com/watch?v=NK5NYTSTIOw[/youtube]

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