Friday, 22 February 2013

Tannerin / Electro-Theremin

About 3 years ago I began thinking about making an electro-theremin (or Tannerin as some might call it) after Gakken released the SX-150 synthesizer kit. I finally got round to it this year.

Basically, I've just replaced the original resistor ribbon and touch pen with a multi-turn potentiometer of the same value (100K) and put it all together in a case. I disabled the pitch envelope as that wasn't needed and added a slider pot to the output in order to give volume control. This is sprung so it will always kill the sound unless held open. I wanted to have some kind of soft control over the volume - a bit like the controls on an Ondes Martenot.

The current set up has a 2 and a half octave range. I've printed out the keys for guidance. It would be nice to have them permanently marked out on the case but I'm finding their position can be prone to wander!

It sounds pretty awful - check the video below 


A cord from an old radio turns the potentiometer.


The cord wraps around pulleys and the tension is maintained by a spring.


The handle and slider - this runs up and down an aluminium runner and pulls the cord to turn the potentiometer.


Placing the thumb and forefinger on each side allows you to see which note you are 'hitting' in the space between.


The slider on the runner protrudes through a slot in the case.


This is the volume control -  a lever is connected to a nylon line that wraps around the slider pot and then to a spring. Holding the lever open controls the volume accordingly.


The controls.


Here's a video of it in action - I'm trying to play along to some simple backing.  It sounds truly awful but some delay and a little overdrive helps..

Thursday, 21 February 2013

Rotary Speaker mkII

This is my new improved rotary speaker - with foot pedal speed control. The foot control simply turns a potentiometer that's connected to a PWM circuit driving the motor speed.

This approach is similar to the treble horn of a Leslie speaker.

Rotary Speaker mkII

A piece of PVC duct pipe bend is rotated above the speaker. There's a paper cup (with bottom removed) wedged into the pipe to give more 'fling' to the sound.

early test

Here's what's inside - a motor and belt which are enclosed in the box. You can see the speaker below.

Rotary Speaker motor box

Foot Controller.

foot controller mechanism

This is the mechanism in prototype.

foot control construction

And the finished pedal.

foot controller

As usual I'm using a Ruby amp to drive the speaker:

Here's a video of it in action with guitar and then keyboards -no other effects.