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

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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

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

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

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

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.

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.

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

Another theremin phenomenon I have often noticed as a designer is when a theremin is angry rather than a happy. To go with that, though I am not a musician, she tells me a beautiful sound is much easier to play as if she needs to sing.

I just wiggle in the pitch field nothing more but in this sound byte she wants skilled hands to express something. I try and fake a bass walk and then she comes alive, this is all natural from nature, no reverb or post processing, imagine what that would add?

If the pitch field were not linear the upper notes would not be just as distinct as the lower notes. My texture knob changes the sound to edgy.

Christopher   

When I began my theremin journey I had never heard of Lev Sergeyevich Termen or Robert Moog, not being a musician. It was Brian Wilson who introduced me to the theremin. Stubborn as I was I would design it my way without looking how anyone else did it. That is why my design is original, invent it? No I discovered it, I let her guide me. To develop my skills, as I had never worked in the electronic field, my first design was done completely using parts I could only purchase at Radio Shack, a popular store in the states at that time. That is why my first avatar was RS Theremin.

Why I dig this up?  I barely remember a simple circuit I discovered back then that would compensate for any thermal drift. You can see at the top of the board the date is 2008. Not sure how it worked but now have the period to review what I was doing. It is about circuit balance more than monitoring, I could adjust the pitch drift to go up or down with temperature rise so somewhere in the middle is balance through counterbalance.

The magic discovered at 900 khz I now realize is a phenomenon, that just happens to be where the parts tuned in at, like she was waiting for me.

My biggest frustration on my theremin journey was I wanted advice from electronic engineers but she would not allowed it.

Notice the board used an 358 & 555 back then... just like now, little did I know how much was hidden in this basic approach at the time, but where did this design come from? I will tell you... Mania.   

Christopher

If the theremin did not have a natural linear pitch field then it would not have been embraced as a musical instrument.

The perfect linearity of the theremin matches the musical scale which is a man made creation. If I adjust my pitch field so every musical note is about ¾” wide the note spread matches the piano exactly. 

The inline series tuning method of bringing the pitch electrode into linearity is like twisting her arm.

The parallel method of tuning I use is like scratching her back, an exchange of pleasure.

In this early model of mine the pitch antenna is within the bamboo and you can see the tuning knob below the dolphin. I am new to the theremin at this time, in my first year, and did not know that my perfect pitch field linearity the theremin was revealing was unusual.

The musical notes are where the graphic shows them, this is when I learn a visual aid takes away from the fluidness of theremin play.

If you want to play notes perfectly then play a piano, why twist her arm?

Christopher