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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 resonates with the
Lev Antenna! 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 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?
| 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 theremin could become
one of the most treasured designs,
it dispels
13 common design myths.
The
new Phoenix Solid State is
even better!
Christopher
theremin@oldtemecula.com
August 15, 2011
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