EWS Box Mod

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EtherWave Standard Pitch Mod

- The Box -

Go to Timbre Adjust

Parts List Phoenix EWS
List is for a Single Board 9.26.21

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

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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 -

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.

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 IF Transformer, the side with two pins, one pin should be cut off & not soldered
or it will short circuit the oscillator.
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This ferrite cup type of IF Transformer is a Must

Box #1 is at Amazon

10.5" x 4" x 1.25"

$20

Box #2 is at Amazon

9.7" x 5.5" x 2.7"

$14

* I have a working EWS to try this on. Ordered the Box #2, now Box #1 seems prettier *

12/01/21 - I am studying a fascinating modification, pitch tuning with a 10 ohm/10 turn potentiometer below L4

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.

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

Succeed you will have something better than this theremin sound priceless! Modern engineers avoid analog and want to make everything digital because that is what they know.
The Oscillators A new design for theremin	The Audio Enhancement under construction
Special Pitch Electrode Electrodeum Pitch Antenna
phoenix-oscillator-theory.pdf	how the pitch field works.pdf
Parts List Phoenix EWS List is for a Single Board 9.04.20	Project Schematic PDF Update Coming Soon

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.