Build an Analog Theremin that Rivals a Modern Day Classic for about $100

Posted: 9/25/2018 8:37:40 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014

We need some new entertainment

Few know what a classic theremin sound.wav was, today they settle for a thin whistle toy or worse yet the sound of a kazoo.

Originally when people listened to the authentic classic theremin in the 1930's some people would pass-out from fear, would your theremin cause that experience. Many modern day theremin designs are giving up this quality... turning the instrument into a gimmick. Is it for profit or out of ignorance?

Here is an analog theremin sound I call "The Angel of Death" passing over Egypt.  (an acoustic trick, don't focus on the noise in the recording)

What makes my theremin more fun the volume control can change the spot light intensity shining up from the floor on the thereminst for drama.

Christopher


Posted: 9/26/2018 5:49:58 AM
gerd

From: Germany (Black Forest)

Joined: 11/25/2017

Hello Christopher,

what about a hybrid-Theremin with tubes for the oscillators & mixer and modern semiconductors for the rest?
There are small and energy saving Russian low voltage tubes eg. the 1SH24B or 1SH29B. The are sold on ebay for about 100$ per 100 pieces.
The 1SH24B needs only 1.2V and 13mA for heating.

gerd

Posted: 9/26/2018 1:31:33 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014

Hello gerd,

If I was in a competition to produce the finest classic theremin sound without the use of post processing or any use of reverb to mask a cheesy sound then definitely my first choice would be vacuum tubes on the front end. Here are my main reasons why from practical experiments.

A vacuum tube is thermal drift resistant, in my designs I could set the pitch on middle C before I went to bed and in the morning when the room was 15 degrees cooler the theremin was still on middle C... barely.

All I need for the theremin effect is two RF oscillators that are clean and do not stall out. When using vacuum tubes they must be shielded (high impedance) or they will pick up noise.

And now the magic of a vacuum tube and it may not be what you think. Used in a RF oscillator I think of them as sluggish which gives that deeper vocal sound. I call it the slower roll-over of the sine wave whereby a transistor is snappier in an oscillator. Even using the same vacuum tube but exchanged with another one I will not always get this effect. I never figured out how to detect the best tube for sound other than trial and error. I do have a very nice tube tester I purchased in 1970 for TV repair.

I was always happy using a 1N914 silicon diode for mixing RF following tube or solid state oscillators. I also tried germanium with no significant improvement. The ideal sound begins with the RF oscillator and the wave shape changing as it passes through diode mixing which adds a bit more distortion; this is where the even harmonics can really develop, why it sounds alive.

After that point everything should be solid-state as that is most practical.

This characteristic is what a digital front-end usually does not capture and why it will sound like a toy making beeps or whistling. C3P0 or R2D2 
IMHO

Funny, I always accused Paul Tanner of making so many believe a theremin was supposed to sound like a whistle and he never played a theremin.

You touched my theremin sweet spot, ok short answers from now on.

Christopher

Posted: 9/27/2018 4:39:19 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014

When I say before Clara I mean not the classic theremin sound which is not a whistle, violin or cello, those would be design flaws along with the RCA buzz on the low end. This is an early build by one of my students. Dana Abbott (RIP). The sound of Clara would develop in my next Phoenix model.

Christopher


Posted: 9/29/2018 2:41:38 AM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014


Hope I am not boring - This is not my tube design but it was the vacuum tube that first demonstrated to me what was special about theremin design. The classic sound was difficult to capture in follow up builds. I knew I was missing a piece of knowledge and around ten years into my theremin journey a TW member had drawn a rough schematic of a simple circuit that I call an emitter follower. Using that I could more easily get the classic theremin sound, sometimes better than others and do it with 100% solid state.


People use to pass out in the audience, thought the spirits were being channeled, could your theremin cause that to happen?

I always accused Paul Tanner of making so many believe a theremin was supposed to sound like a whistle and he never played a theremin. His invention was the turning point when many began to call anything a theremin including cell-phone Apps. Paul had brought more awareness to the theremin than anyone had before him. Expect more from your theremin than R2D2 on a kazoo. As a programmer I do enjoy digital in the proper applications.

I found another video of someone building one of my earlier theremin designs which is before Clara, the below sound recording is poor.

Christopher

My first designs did whistle... but it was a fat whistle. Also Dana is using my Auto-Vibrato circuit. You can see the Pitch rod is a tight coil on a wood dowel for perfect pitch field linearity which is one of several theremin phenomenons waiting to be discovered.


Posted: 9/29/2018 4:16:51 PM
ILYA

From: Theremin Motherland

Joined: 11/13/2005


Christopher,
is it seems to me, or in the last video my ear hears a ghost tone (in minor third, approx.)?


Posted: 10/7/2018 4:34:32 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014


If I wanted a realistic Cello Sound I might go with an acoustic resonator1 .mp3 or resonator2 .wav off the output of an EWS... Link

* * *


If you find this sound byte interesting here is one way you can get there. I have mentioned over the years that Clara’s voice was a gift to me. I have a few of these boards available. Each build requires two boards, one for pitch and one for volume. Single sided PCB, also make your own with an iron-on PDF is available. Notice the lack of reverb to mask nasty, how gentle and intimate the tone could be in good hands. I can only fake playing.

Christopher
Hwy79.com

The Theremin is a Simple Concept - Here I am adding power to oscillator section for testing.

There is no magic in using specially wound coils or old parts from the past, that is theremin myth.


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