September 18, 2023

This volume control was designed by oldtemecula and developed from the research of elektrouwe at Theremin World & Kulturgüter-Schuppen  Volume section add-on by Christophe S Becker  (oldtemecula)

3" x 5" or 76mm x 127mm

Left side of board above schematic - Down below is the right side schematic of the above volume section -

Wires:

Green must be installed so ground is available to all parts of the board.

Yellow is for connecting to the Volume Control section. 

Another build could use the left side of this board without the volume parts for a rough theremin & sound. 

Gray is only used when interfacing with the Theremin Phoenix board using a short TRS cable board to board.

Pitch Preview remains On in sound. Sound is at the Tip-5 & Sleeve-1 of the bottom TRS jack.

The white circles indicate where terminals can replace TRS jacks.

Iron-on PDF - printout PDF for home board making.  (found in this Iron-On folder)

There are many YouTube videos demonstrating how to use PDF's to make PCB's. Like this one. 

Gerber Files - for a commercially made Volume Control 3 x 5 board, always check the date for the most recent. 9/16/23 (found in this folder)

Mouser Parts - List is about $25 of stuff. On the list for $4 more are two drill bits. .033" & .052" 

I used the LM2907 configuration on page 15. Circuit design may need to be modified.

Datasheet

A TRS Jack is used so a break-out cable can be used. Plug the TRS side of the cable into the board and one mono plug into the sound source and the other end into an amplifier. A resistor in placed in parallel with the Amp side of the cable to eliminate high impedance hum or hissing when the sound is quieted

Breakout Cable  3.5mm to 1/4"    -       Breakout Cable  3.5mm to 3.5mm ebay

Terminals can be used in place of TRS jacks.

  Features:

  Mute switch.
  Pitch Preview Jack.
  Volume direction reversing switch.
  Null Point LED indicator, great for tuning when mute.
  
Optional - C9 Blue is a 5pf or 10pf variable capacitor added to the board for easier fine tuning from Amazon or ebay

Optional - C9 trimmer capacitor .4 - 6pf ebay

If using a variable capacitor then use the two 390uh choke/coils. The two IF transformers are then not used as they might not work anyway! 

The 390uh coils have a very low resistance (1.28 ohms) and are shielded which is better for this circuits operation. 

Pitch Board - If the design is used for this then change C1 & C7 - 47pf with the two 75pf capacitors (yellow) on the parts list. My goal is ~900khz so this pitch circuit might be used to drive the Electrodeum pitch antenna for ideal pitch field linearity. This change also separates the Pitch & Volume frequencies so they do not interfere with each other.

Vactrol VTL5C1 found at ebay. The higher numbers are too slow. Like 5C2 & 5C3.

The way I understand things switching ground, yellow with green wire determines if approaching the volume loop Volume goes from On to Off or else Off to On.

The green LED should be On at Null or no signal as sound can pass through, LED dims when the sound is reducing.


I make no claims you will succeed as it’s a theremin, you must be invited.

This project was fun for me and I wish everyone the best of luck. 

Christophe S Becker (oldtemecula)  (RS Theremin)

Used TinyCad to create the schematic on the left side for the add-on Volume Control parts.

The sound sample below is what the Volume Control along with the proper Theremin Phenomenon design gets you, pitch & volume is about $100 in parts.

The swan song is a metaphorical phrase for a final gesture or performance given just before retirement or death.

The Swan Song 

Performed by Valery Shamarin using the Theremin Phoenix - Christmas 2020

- The Phoenix Pitch Board is $70 in parts -

There is a spiritual aspect to the Theremin Phenomenon and this is why most engineers are unable to figure it out.

- So they go with digital imitation where they lose something, never hearing or understanding the difference -

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- Let us not forget the true Theremin Phenomenon -
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chris@oldtemecula.com
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The Phoenix 2020 Pitch Board Website Download
160 meg Zip file

- Save this info to dig through for Future reference -