<=RS Illusion Updated 10.19.08

VAPP

VAPP - Volume Amplification & Pitch Preview
Hands free Volume Control for the Theremin

100% Radio Shack by RS Theremin

"This works excellent with any theremin that is pitch only."

*  *  *
Schematic (61k) PDF drawn by Don Parrish-Bell
.



LDR raw  vapp_board.mp3  (192k)  LDR reverb vapp_boardr.mp3  (192k) 

Undistorted Dynamic Range vapp_board1r.mp3  (246k)

No laughing, I am not a musician!

.LDR means Light Dependent Resistor

This technique of using an amplified LDR surpasses the control of the RCA hoop style hand capacitance method of volume control. The amplified LDR works excellent in normal room lighting without any external lenses or light focus. Use the lighting you can "read your music by" for excellent volume response.

As your hand lowers to cover or shadow the LDR photocell, the volume quiets. The resistance will increase to several mega-ohms. Greater than a  12" window of control from Full Volume to Total Cut Off is possible. 

This Illumination volume method is one step away from the "Future", polyphonic control and real time shaping of the vowel sound of the theremin voice.

 Using a volume control on a separate stand from the pitch stand solves the problems faced by left handed Thereminist. This also allows for better volume control positioning for playing those outside lower notes.

Features: 

 * On/Off LED indicator
* Mimic the RCA volume hoop control, no need to tune it!
* Completely distortion free across the volume range.
* Pitch Preview with a panel mounted volume adjustment.
* Line-Out with an adjustable level panel mounted pot.
* Mic-Out with an adjustable level board mounted pot.
* Mute Switch with no detectable switching noise.

Note: The two solder pads to the left of the R5 - 4.7k resistor are not used currently.

Easily use the full range of volume, play at full volume, melt to the quiet side or complete silence.  

This LDR setup works excellent in normal room lighting. You could mount the LDR sensor on the back side of the forward rim of an RCA style volume hoop and mimic RF hoop control with a more controlled response. The connecting wires can run inside the hollow volume hoop.

Your RS Theremin can have an adequate ground through the VAPP board connected to any amplifier using a three prong grounded wall plug.

You can adapt the Radio Shack 274-249 stereo jack by drilling 3/32" holes through the *large pads. The Tip connection uses a jumper wire to the board hole with the circle around it on the silkscreen. Fold down the center ring tab to match the back sleeve tab on the jack for mounting on the board.

The Mute contacts need a switch or jumper wire installed to pass sound to the Line Out jack. 
The Pitch Preview and Mic-Out "are not" muted.

* Preview Output - Audio is supplied to the Tip & back Sleeve of the stereo jack. Use an earpiece with a mono-plug or a stereo headphone for sound out one side. Panel mounted volume pot.

* Mic Output - Audio is supplied to the Tip & back sleeve of a stereo jack so it can plug directly into your computers Mic input of your sound card. Board mounted Mic Level adjusting pot.

  Line Out - Use connecting wires to a 1/4" mono jack 274-280, the tip connection is circled.

* Power Terminal - Use the standard two terminal 276-1388 for a Pos & Neg battery connection or use an adapted stereo jack 274-249 if you want to share Audio and Power with Switch on the same stereo cord with the RS Illusion theremin and separate volume stand. The Tip is +V, the center ring is Audio and the back sleeve is -V.
Home Depot  
has a package of two for $5    

R1 - LDR Photocell - remove it from any bathroom plug in nightlight, they worked the best. 

LDR Range is greater than
2.2K to 2.2Meg resistance.
Having the volume control separate from the pitch control base allows for better placement of the two controls.


The Radio Shack 5 pack of CdS cells 276-1657 are not effective. They do not have a wide Light to Dark response resistance.

<=RS Illusion