Forbe Tube Theremin for sale

Posted: 12/7/2009 8:26:22 PM

From: Brooklyn,NY

Joined: 12/1/2009

I need to raise some root for the Keppinger tube theremin that I want to build, so I'm parting with some of my old toys.
This theremin is built from Doug Forbes' circuit, found in the schematics section of this site. In addition to a 6x4 rectifier tube, the design uses four commonly available 12au6 preamp tubes. Small chassis mount tuning coils form the heart of the oscillators. The steel chassis is mounted in a hand-made mahogany cabinet with matching turned mahogany knobs. The pitch and volume antennae are made from hollow brass tube closely resemble the shape and size of RCA. The tone is very rich, much sweeter than my etherwve clones.
I built this a few years ago and after getting it running made some improvements:
I wound a large coil and added in line before the pitch antenna. This greatly improved the instrument's linearity.
I also added a mechanical srting and pulley system from a radio tuner. This gears down the tank cap rotation and allows the player to more finely and acurately tune the pitch.
This piece come with lots of extras: tubes, coils, full documentation of schematics, parts lists, ...everything I have for it.
This is very cool theremin. Its obviously unique, beautiful, and it deserves a good home. The simple design and layout make this theremin an excellent platform for further modifications and experimentation.
Check out pictures here:
forbestheremin (

volumeloop (
Feel free to contact me with any questions.
The estimated value for parts alone is about $250
please make a fair offer. I will ship but due to weight and sensitivity, I would reccomend that it is picked up in person. I live in Brooklyn, NY
Posted: 12/7/2009 10:27:40 PM

From: Brooklyn,NY

Joined: 12/1/2009

here are some more pictures. You can see the added pitch coil and the tuning mechanism inside the cabinet
inside (

inside2 (
look through my flickr photostream...
There are more photos of this and other theremin that I built on pages 4 and 5, the rest is mostly artwork.
Posted: 12/8/2009 4:40:03 AM

From: Miami & Paris 50/50

Joined: 8/7/2008

Please contact me :

Best, Marc
Posted: 12/8/2009 8:31:57 PM

From: Toledo, Ohio United States of America

Joined: 2/22/2006

I must say that the Theremin you have created is an electro-mechanical work of art! Your skill is humbling! I bow to you!

I just wish that all in Theremin World could hear it's voice.
Please, set some sound file links on this forum page, so that all here may adore it's dulcet tones.

Good Luck!
Posted: 12/8/2009 10:45:19 PM

From: Brooklyn,NY

Joined: 12/1/2009

thanks so much.
as for that sound clip... im working on it.
while i may have been able to build this thing, the documentation stuff i find a little tedious and daunting. It should be recorded through an amp by a mic. I have a multitrack recorder, but i gotta relearn how to use it. sigh... so you see where im at.
Posted: 12/13/2009 1:19:48 PM

From: Brooklyn,NY

Joined: 12/1/2009

This item has just been sold and is off to Paris.
Thank you, Marc.
Posted: 12/15/2009 4:04:08 PM

From: Colmar, France

Joined: 12/31/2007

That's fine!

So I will have the occasion to see and to play it one day since Marc asked me recently if I would be ready to look after his theremin collection in case of technical problems. I naturally agreed! ;-)

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