Building "Linearity" into a Tube Theremin

Posted: 12/16/2023 7:45:57 AM

From: Anacortes, Washington

Joined: 5/5/2009

Does anyone have a circuit design additive for the TUBE theremin that is at least equal to Clara's Tube theremin? I am building a Clara-RCA tube theremin and am a newbie at vacuum tube technology and design.  Nevertheless, I am very good at following schematics instructions. I need PICTURES of a circuit (not verbal technical terminology) that I can ADD to the circuitry to make linearity better spaced. My tube theremin high octave close to the antenna squeezes down to tight, and is almost impossible to play.
If anyone has any ideas, work off of John Polstra' schematics or Clara's - Author Harrison's.
This will help very much.
Please reply with ideas and some pics. 
Volume sensitivity.
Anyone got a circuit design that can be added to the volume circuit in a Tube Theremin?
Take for instance, Clara's Theremin schematics analysis done by Author Harrison and see if it can be modified
to play volume quicker for better staccato.
I want to make a tube theremin play as close to the Moog Big Briar 91A as possible.
See what I mean =

Posted: 12/16/2023 4:48:50 PM

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014

Ross . . .The sound of a tube theremin can be duplicated or made even better in solid-state. JPascal & I myself have demonstrated this. Everyone has their own taste in what sounds good. A beautiful theremin sound comes through a very narrow window in design which is not easily accomplished. Not all tubes have the affect on sound as you might hope for.

What I can help you with is ideal pitch field linearity. In this video below my friend Valery Shamarin & Peter Theremin in St Petersburg were able to play my design right out of the box. One of the mysteries of the Theremin Phenomenon is ideal pitch linearity beside a beautiful natural sound. I use to call it perfect linearity but that upset the cynics around here.

If you operate your tube theremin pitch side around 900 KHz then use the same antenna method seen in the video above. It is parallel tuned to the main oscillator which is “much more forgiving” than the EWS series tuning.

Perfect Pitch Field Linearity is either on or off, there is no almost linear.

Lev Sergeyevich Termen referred to the pitch antenna as an electrode so my antenna circuit design is called the Electrodeum.

The webpage could use an overhaul but you will get the idea.

Merry Christmas


Posted: 12/16/2023 10:18:13 PM

From: Anacortes, Washington

Joined: 5/5/2009

Hello; Ross here. I have some questions and a few requests.
[UPDATE: I found my Keppinger Schematics!!!]

I have what I remember is a Mark Keppinger Tube theremin (chassis') that uses the 

6sn7s, 6J5, 6H6, 5Y3, 0D3, and 6V6 tubes.

The tone sound is as close to Clara as I will get at the moment- it's acceptable.

[Am also playing with building an RCA that I use to play that the Bellingham Sparks Radio Museum under John Winters.]
BUT my "Keppinger?" chassis linearity is horrible - maybe something got wired wrong? Low octaves are nice but can get too extended. The high pitch octaves are impossible to play the closer you get to the pitch antenna.
Q. Does anyone know tube circuitry enough to supply a additional circuit or repair to extend the octaves and space the linearity out more evenly on the Keppinger chassis?
I like to play Classical pieces and am struggling to play this thing.
I would appreciate any help you all can give, short of a free shovel and grave plot. :o(
We know enough here to modify the chassis but are not circuit designers.
Any "DRAWN schematics" can be interpreted- I DO NOT know how to read "verbal" vacuum tube circuit technical language.
I can easily READ any visual schematics.
Please if anyone can help send some PDF schematics?


Posted: 12/16/2023 10:23:25 PM

From: Anacortes, Washington

Joined: 5/5/2009

Ross . . .The sound of a tube theremin can be duplicated or made even better in solid-state. JPascal & I myself have demonstrated ... Sergeyevich Merry ChristmasChristopher

Thanks Christopher.
For now I am stuck with messing with tube theremins.
Mine is a Keppinger.. can you help me with the following post on Keppinger questions?

Posted: 12/17/2023 12:20:43 AM

From: Northern NJ, USA

Joined: 2/17/2012

"We know enough here to modify the chassis but are not circuit designers."  - weirdvideos

Aye, there's the rub.  You need to know enough about electronics in general to figure these things out on your own, a journey everyone has to take.  It requires perseverance to discover there was no holy grail in the past, don't get trolled by those who claim to have found it.

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