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use Ctrl-F5 to update this page
EtherWave
Standard Pitch Mod
- The Box
-
Go
to Timbre Adjust
Parts List Phoenix EWS
List is for a
Single Board 10.10.20
The
Complete EWS Build List
Extra Notes Found
Here
12.23.20 -
I still need to take a picture of the EWS three wire TRS connection -
- My
original theremin design is not easy... only because we are human and
make mistakes -
EtherWave
Standard Schematic
- This idea
is New as of 8.26.20, needs study -
Go
to Original 3.04.20 Board
.
The
Tuning Pot & Tuning LED will be on top, with the Electrodeum
Pitch Antenna mounted off
the side of this box. The tuning LED allows tuning without listening to
the pitch preview while Mute. This
Phoenix Mod connects to the EtherWave Standard using a single TRS jack, no
EWS board
removal
Voltage
is taken off both sides of the EWS capacitor C19
+12 TRS (tip)
-Neg TRS (sleeve) (ring) = Audio or Pin-7 as seen in right image. -
earth ground should already be on the negative rail or sleeve -
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This
approach continues to use the EWS volume
control like normal
Features:
Null-Tuning, Mute Switch, Pitch Preview, Adjustable
Timbre (sine to
vocal), using the Electrodeum Antenna/Electrode the Pitch Field
Linearity will be similar to the E-pro.
Pitch
Drift is suppressed with Pot-3, seen as blue Pot below.
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This is
the actual Pitch Board as of 9/19/20 - Breaks out of Null below 30
Hz Smooth
Click on
image to enlarge
Note:
On the 3.04.20
board the two opposite IF
Transformer pins
should be cut off or not soldered.
.
This ferrite cup type of IF
Transformer is a Must
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Box #1 is at Amazon
10.5" x
4" x 1.25"
$20
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Box #2 is at Amazon
9.7" x 5.5" x 2.7"
$14
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* I have a working
EWS to try this on. Ordered the Box
#2, now Box #1 seems prettier *

Red X
are parts not needed, Left side blue = R8-
3.3k, R20-3.3k, R25-
220, parallel C29 with a .1uf
capacitor
* The blue line under
the 555
on right side of board is a 100k resistor connected at R2-
220k
to top of R31- 33k (This
area will be modified)
C5- .1uf
lower right
needs connection relocated.
U2a is used as a 1:1
signal buffer for the Pitch Preview & Audio Out
unmod-pitch
- Press Ctrl-F5
to update
image to 10.30.20
-
.

- Click on image
for clear enlargement -

A few parts are not needed on this
board seen with the red
X.
Made a new parts list and will post a picture of board and what is needed when I get there.
Parts List Phoenix EWS
For this to work
you need to remove the EWS Pitch Antenna and then use an alligator clip
connected to the antenna threads back to ground through a .1uf capacitor
to block any dc path. (Ant-Gnd)
The
Electrodeum Pitch Antenna is used for ideal linearity, it is mounted on
the new box.
10.11.20
Notes
U4 bridge IC is not mounted on
the 3.04.20 board,
use its pads for the half wave dc EWS +/- power input.
* C6, C5- .1uf
& R7 becomes .1uf cap are
repositioned as per the blue lines. R38-100k added to the bottom of
board or enlarge hole near R32 to mount on top.
At long blue line mount a
220uf axial capacitor across for Pitch Preview signal at TRS J3.
A Mute Switch
could be added after the Line Out potentiometer. Doing
it this way will most likely cause a click in the sound if your hand
is not holding the sound quiet at the loop.
Once everything is
working good it would be more solid to solder parts directly to the
board that are in a terminal. The Oscillator Section would be most
important.
The Phoenix Electrodeum
board uses less than 35 ma. You want the least workable voltage across
the 7809 for it to still work properly 11.5v to 12v. This keeps unwanted heat
at a minimum in the box.
To accomplish this 11.5v to
12v use a 3 watt
150 ohm resistor on the EWS side female TRS jack Tip connection to
limit the voltage to 12 volts at The Box and for safety.
- See
this example -
EWS 18vdc/150R wire
wound 3 watt resistor to drop voltage to ~12vdc and for protection.

The
ideal Pitch Wave Shape, the droop is throaty, the upper skew
is even harmonics. The
Timbre Adjust below bends the wave form in many other ways.
Timbre
Latest
as of 11.03.20

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Here
are never done before Phoenix Theremin concepts
1. The Becker Electrodeum is a parallel tuned electrode
or Pitch Antenna for ideal Pitch Field Linearity.
2. The
use of L3 - 3.3 mh
choke with tickle wire is to sense the RF from L1 & L2.
This approach eliminates the need for buffer components with more
control over the final audio wave shape.
3. The use of
the VO618A opto-isolator driving the 600 ohm 1:1 transformer to add
brightness the sound.
4.
Thermal Drift Control - This is done with Pot-3 by balancing the
voltage drop across both transistors. Most drift comes from the PN
junction capacitance.
Latest Up
to Date Notes:
2.03.21
If using IF transformers the secondary is not used so the copper trace
to one of the pads
of the secondary
on at each transformer must
be cut so the
secondary does not short out the oscillator circuit.
2.03.21
The Pitch Board must use the recommended IF Transformers or you will not
get a frequency that breaks out on Null or Zero Beat below 30 Hz. These
IF are not necessary on the Volume Board.
2.03.21
There are two methods of creating a signal that properly turns off the
Vactrol which is normally On so sound can pass. The most sensitive
method is seen in this
video. The oscillators are more tightly coupled breaking out of
Zero Beat around 1 kHz with a 5 kHz range. This needs more explanation
2.04.21
Experiment: Replace
C17 & C19 with 3300
uh chokes in parallel with the IF Transformer to drop frequency down
to around 300 kHz and see if the Electrodeum Pitch Antenna works off the
third harmonic of the oscillator. This will further reduce thermal drift
and could have other benefits worth study.
2.04.21 A
device like
this could be used for remote Pitch Tuning when the theremin is
mounted in a sculpture or used in other applications.
2.09.21
It is best to have the Power
Supply components on
the Pitch Board for easy testing of the first board build. Also
this prevents any poor connection effects getting into the sound cause
by the board to board TRS jack connection.
- The
Power Supply is installed on one board only -
2.09.21
If Pitch & Volume boards are place in a EtherWave Standard box the Power
Supply needs to be on
the Volume Board so it does not get in the way of the EWS front panel
knobs.
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