The theremin, a musical Instrument to challenge us all!

 
Tube/Valve Hybrid Lev Antenna

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The Vision . . ."True beauty is hidden in Simplicity"

My last project was to breadboard a hybrid Tube/Valve pitch oscillator and see if "Perfect Linearity" could be found. This would clarify if the phenomenon of LINKS and the Lev Antenna was unique to transistor oscillators or could it also be demonstrated using a tube/valve oscillator. 

The answer is Yes!  "Perfect Linearity" is possible with vacuum tubes!

Most of my theremin experiments over the years used Hartley Oscillators operating between 800 kHz and 1000 kHz. This higher frequency allows the design of the Lev Antenna to be more practical. I found that using hand wound air coils in the oscillators was a poor choice because it limited Perfect Linearity to just over three linear octaves and added to pitch drift. My original RS Illusion transistor theremin revealed that using High Q ferrite coils would give more than five linear octaves over the same air core coil setup.. 

A pitch oscillator between 875 kHz and 925 kHz Lev Antenna excitement!

This five plus octave range was also found in my scratch built tube/valve hybrid theremin which also uses ferrite inductors. Using tubes for the pitch and fixed oscillators has a much more subtle Null break point and a better symmetrical wave shape in the lowest notes of the audio sound, compared to transistors.

With my musical crudeness in a 18" pitch field in the sample below I will make a one octave jump by closing my fingers then rapidly opening my fingers within 1" of the pitch antenna. I will repeat this while moving midway back in the pitch field and then near the lowest octave. Each time the same hand/finger movement is used. This is one of the easiest methods of validating any theremins pitch field linearity. I am watching an on screen frequency counter.

Linearity Test.mp3 (200k)
Raw vacuum tube sine wave  
A linear 2400 hz down to 100 hz

Perfect linearity remains no matter what size intervals or octave widths you enjoy playing. This Lev Antenna phenomena once set does not need retuning. It's tuning bandwidth is broad and stable.

My scratch built hybrid theremin uses one vacuum tube for the pitch oscillator, one tube for the fixed oscillator. This hybrid theremin pitch field has Perfect Pitch Linearity and cost less than $200 to build plus seven years of learning the simplicity of how theremins work. My design does not need variable capacitors or exotic variable inductors. It uses simple solid state tuning I designed, the tuning knob can be twenty feet away.

My tube/valve pitch method is not available to the general public currently. 


Clara Rockmore is the #1 theremin virtuosa, but how did Lev Sergeyevich
 create her "authentic" natural golden sound?  

Sound of My Hybrid  mp3
Sine Wave  (188k)
<=Timbre Knob=>
Adjustment direct line-out
Finding The Voice mp3 (470k) 
Authentic No Processing!  
6.03.13    
If you would enjoy playing this harmonically rich theremin voice with its perfectly linear pitch field, then I will do my best to organize it as a "build it yourself" project costing less than $200 usd in parts. This cost includes dual tube/valve pitch oscillators and an independent RF volume control board with an adjustable 10" down to 2" shading area. Most of the parts you purchase from Mouser. At no cost make your own pc boards from my PDF's. In the future I will have commercially silkscreened and drilled printed circuit boards, this will add to the overall cost. Five Boards = 4 - 3"x 6" and 1- 3"x 3".

This RS Theremin could become one of the most treasured designs,
 it dispels 13 common design myths.
 

The new Phoenix Solid State design may be even better!

The Red Wire Connects to the Pitch Antenna

Above are two oscillator pc boards & Pre-Amp

On the forward right of these two 922 kHz osc boards you can see the small IF coils used! The entire hybrid pitch section is made from these three 3" x 6" pc boards . Power for everything including the independent volume control comes from the two pcb mounted osc board transformers. 

The chrome rod on the left is my independent RF volume control. The secret to rich theremin sound is the soft roll over of the tube/valve and "nothing" to do with big coils. As you can see I am using tiny IFT coils in 922 kHz oscillators.

I posted a list of 13 theremin design myths to TW once but the engineers got too upset for me to post it again. The forum host needed to delete what I suggested, it did not support the engineer models? In theremin design you must allow the theremin to guide you as she will show you most often what does not work and that most methods have an un-musical sound. Modeling relies too much on GIGO which does not encompass all the circuit influences found in analog oscillator design. That is why engineers and their models rarely if ever post any sound bytes. They insist modeling saves time. o-;  

Most theremin engineers spend most of their time trying to overcome the negative issues they created for themselves. She (theremin) has attitude and if you're not invited she will make you suffer.


Lev Antenna Spring Coil

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