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The
resistor/capacitor input values are 1uf & .22uf capacitors for a 15 hertz rich low frequency response.
A complete solid state
theremin can be built using two of my identical
pitch/volume circuit boards with a sound like the Sample 1 below or various other timbre. Start
by making the Pitch Only board first and attaching 12v
power to the
right side diode and 7809 9v regulator (No Vactrol
needed on the pitch only board).
Sample
1 .mp3 280k
When
used
for Pitch: Change the Pitch
Oscillator board C17 & C19 to 47pf to move the
operating frequency closer to 900 kHz, away from the lower volume osc
freq. Then while tuning the coils move the frequency as
close to 900 kHz as you can. This is Lev Antenna range.
A phenomenon unto itself!
For the
smoothest sound add a jumper wire on the Pitch Only Osc RF
section at Jmp 2.
This grounds the coil's shield. Don't do this on the Volume
Control board where a sharper wave shape is preferred.
Take the line level audio output
from the Audio Out on the right side of the pitch board at A or B
(each have their own sound character) and
connect it back to the pitch board stereo-jack terminal # 2 solder pad. Now
use several feet of 1/8" stereo cable with male plugs to connect the
Volume Control and Pitch boards together. Having a separate
volume & pitch allows you to position the theremin anywhere around
you.
When used for Volume Control
this is stand alone, independent of the pitch board, only
connected with a stereo cable between them for power and audio
signal. C17 & C19
are 100pf for a frequency of 740 kHz which was
measured at the base of the Q2 & Q3 transistors.
Mounting the full length volume pcb to the back of a
3' standing hardwood panel is also clean and ideal look. The
volume hoop can mount securely to the top of this wood panel. You can also cut
to your wood panel to your proper height or mount
your volume pcb on a 10" piece of thinner
material so your control knobs mount through properly and then
use one of those 1/4-20 flat head T-nuts in a glued on block of
wood so the overall volume control can mount solid off of a camera
tripod with their swivel head positions. Female mic
hardware is also available for using a mic stand.
The stereo jack
with its attached cable is
the
connection from the above volume control board to my separate theremin hybrid pitch section.
The cable
also brings power and the tube/valve theremin audio to this volume
board. Listen to the amount of volume shading
possible you can achieve from the above volume board. My tube/valve
sound method in this sample is currently not available!
tube/valve sound .mp3
135k
My tube/valve pitch method is not available to the general public
currently. If you have a strong electronic background, engineer
or hobbyist and have interest in my theremin hybrid project the enigma,
email me your project background. Maybe we could trade
your good schematic drawing of each board, then I will send you
silkscreened and etched that particular board you have drawn.
You would drill your own holes. Here is a sample of past
schematics engineers have drawn for me. My original RS
Illusion Schematic.
As
a Volume Control: Install the V1 Vactrol at the bottom of
Volume Control board. The Vactrol is an isolated variable
resistor using a PWM LED driving a CdS Cell. You could add slight
modifications (37k resistor) to create a variable proximity Control Voltage
output level (0-9 volts) but that is a discussion
for another time. The Vactrol resistance swing in this circuit
with the indicator LED 1 on (max freq) is about 15k up to 15 meg with
the Vactrol internal LED off at the Null point. The new Rev N
or later board has a volume hand motion-reversing switch with no retuning!
The volume control
Vactrol Analog Input works best at 3v p-p or less. The
controlled Audio Output is to the left of the Vactrol from the
output jack.
If using this board as
pitch board the
signal drive level to your amplifier can be
ideally adjusted using Pot 2 on the Pitch board where the audio originates.
LED 1 in the lower right corner of the Volume Control
board turns on when the Osc heterodyning
breaks out of Null. This indicator LED 1 is driven by a 9 volt
PWM Schmitt
Triggered square wave output from pin 3 of the TLC555. This
is a great tuning and response indicator for the silent volume control board.
The advantages of a
stand
alone volume control are that you can place it anywhere. If left
handed move it over. I like to play standing
sideways so I place the hoop opposite the theremin or behind to
my left side.
Move it away from the theremin for better access to the lowest notes and full range.
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