Goals for a TW Theremin

Posted: 10/4/2012 5:23:34 AM
w0ttm

From: Small town Missouri on Rt 66

Joined: 2/27/2011

It looks like a transistorized RCA will be the first prototype.

I have a day off Thursday and was hoping to get at least an oscillator running, if not a working pitch only theremin. I'm winding the oscillator coils only because I don't want to wait for store bought ones.

I thought I had suitable FET's, but due to an old eyeball error, I don't. Radio Shack usually stocks them, but my local store was out today.

I'll try another store tomorrow.

I'm very seriously excited about this....Rob.

 

 

 

Posted: 10/4/2012 5:48:38 AM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

I'm somewhat amazed at how quickly this is coming together!  You folks rock!

Posted: 10/4/2012 8:06:36 AM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

"But it seems like we are all keep bringing up all our same pet concepts. Id say, lets build a theremin that sounds like an rca/claras, to the performance specs i mentioned if there is no objections (minus the timbre, mostly there i was thinking of, i believe, the paia theremin, that suddenly goes from violin-like to suddenly flute like which is awful) and to the interface specifications, which fred should probably propose, in whatever the best way possible, with open minds. Its an interesting challenge." - Nieradka

I think the "disharmony" of requirements will always be there - there will always be those (and I count myself among them) who want a "modern" instrument with more sonic possibilities.

I think the "RCA Clone" is more an "ofshoot" from the main "TW Theremin" than the TW Theremin - And to me, the real excitement comes from the understanding I am gaining - the "peek" into the "Mind of Lev" if you like - This is why I am into electronics, its what fires me up - I get more of a "buzz" from looking at an awesome simple design ond having those "eurika" moments when the scales fall from my eyes, than from looking at some "amazing" super complex processor "designed" by a crowd of unimaginative engineers plugging blocks together with a CAD..

As I see it, this "RCA Clone" (if it really comes together - but please remember, at this time it is only a simulation ) could be built as a stand-alone, single board theremin.. I do not see it as the basis for a modular theremin, although useful sub-circuits could possibly be 'extracted' - I think that "compliance" with the "as close to an RCA as possible" possibly limits its potential in terms of being part of a modular.. Also, its limited number of playable octaves will make it unatractive to many who want a "modern" theremin, and this cannot be changed without losing the RCA qualities*.

Once I have fully understood the RCA, I will examine any data I can find on Levs other theremins - Clara's etc, and see what I can find in these - Anyone having any technical information on these, I would love to see it.

*it can be, but I cannot share how.

Fred.

>> As I see it, the TW Theremin needs "Goals" and "Specifications" etc - A RCA Clone has these already defined - it is simply to design a theremin which is based on available solid state and other easily available, not-too-expensive components, which is not too complex, is reasonably easy to construct and tune; - But, over-riding all other requirements, must sound and behave and "be" an RCA theremin as closely as possible.

 

Posted: 10/4/2012 12:57:37 PM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

" the interface specifications, which fred should probably propose " - Nieradka

Thanks for your vote of confidence, but I must decline..

I am walking on an extremely thin tightrope at the moment, trying to balance my interests with my passion for moving theremin development forward.

I do not want to talk about it - both for commercial reasons, and because I have so often in the past spoken of my developments and been unable to deliver - But I must declare a possible conflict of interests.. I will briefly describe what I am doing, and why there is a potential conflict - but please understand that I cannot discuss anything which I say here any further, so no questions here or by email from anyone, please!

I have developed a modular theremin - this theremin has a front-end which provides adjustable linearity and sensitivity, and allows register switching.. from this front-end, and has a master mixed-signal theremin voice (I have published schematics for this voice on TW previously). One can plug in analogue (and mixed signal) theremin "slaves" - These are complete theremins, containing their own analogue pitch and reference oscillators, mixers etc - the only thing they dont contain is the circuitry for the pitch or volume antennas* this is for simplification / economics - Theremins whose tone depends on antenna circuit interactions can have these fitted.

I have developed a way to lock these slaves to the master frequencies generated by the common front-end, and the interface also allows the slaves to be detuned WRT the master - precisely detuned, in semitone steps, with tracking accuracy of better than 2 cents - they can also (optionally) be detuned with a potentiometer over one octave and each 'slave' has an independent register switch giving +1 octave, normal (tracks master) and -1 octave .. the tuning switch gives one octave of 1  semitone steps down from the selected register, or this switch can be replaced with a potentiometer giving 1 octave of detuning. - These theremins are free phase with respect to each other, but frequency locked to within 2 cents. The interface circuit which controls the theremins acting as 'slaves' can be applied to any theremin - one could take a tube RCA, fit it with the interface, and drive it from my front-end. As each 'slave' can be independently detuned, "polyphony" is available - But it is not true polyphony, as there is no simple way to control the "slaves" independently (there would be if theremins were played by an octopus - its the control mechanism and physical factors which are the limit, not the electronics) - I can, however, independently vary the volume mix of 2 slaves "sets" using hand (x axis) movement on the volume antenna, and could possibly extend this to 4 by also using 'y' axis movements.

I cannot undertake an interface specification - because I would need to limit this.. What I have done above is actually extremely simple, and the TW theremin could easily do everything I describe above - All it needs is one simple idea, one Eurika moment .. If you come up with it by yourselves, well, I would have mixed feelings (in fact, if you go over all my past postings [LOL - take a week off work ;-] you may just catch the idea) - but at the moment I cannot give it to you.. If my deal falls through, I might!

I also wish to declare that I fully intend to use the "RCA Clone" being developed here, as a "slave" module, and sell such a module if my above development comes off.

Fred.

Posted: 10/4/2012 1:03:51 PM
AlKhwarizmi

From: A Coruña, Spain

Joined: 9/26/2010

I have no idea of circuits, schematics, etc. but I just wanted to drop by to say that, if you manage to design a theremin that sounds similar to the RCA theremin for a decent price, and sell it in a "finished" way so that we don't need to assemble anything or have technical knowledge, I'll buy it like there's no tomorrow.

Posted: 10/4/2012 1:26:54 PM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

"I have no idea of circuits, schematics, etc. but I just wanted to drop by to say that, if you manage to design a theremin that sounds similar to the RCA theremin for a decent price, and sell it in a "finished" way so that we don't need to assemble anything or have technical knowledge, I'll buy it like there's no tomorrow." - Alkhwarizmi

Yeah - Im sure many people would..

And I think that this happening is now inevitable - The RCA's main secret is probably out now, it may just be that its operation is being understood for the first time in many decades -

And the possibility for commercialising this will be obvious to every theremin developer and many "wannabe" developers, and theres nothing to stop them.

And I think this is great! - I would never have looked at the RCA again, had it not been for my respect for Uncle Howie.. I would never have bothered re-simulating my original schematic (which was incorrect, based on incorrect assumptions everyone had made, and incorrect component values derived from how people believed the RCA worked, rather than by measurement) if it hadnt been for Hobbs pushing me on this point and quoting Uncle Howie again.. Then Rob (w0ttm) voiced a possibility I had seen (series LC) but was not able to embrace because it was so "stupid" LOL ;-), and quickly calculated thev real tank inductance values..

Yeah - This is everyones! Its one of those rare moments of Synergy (strangely, the name of my new theremins - I registered SynergyTheremins.com a few weeks ago) which make life exciting!

And I am buzzing ;-)

Fred.

Posted: 10/4/2012 7:31:55 PM
w0ttm

From: Small town Missouri on Rt 66

Joined: 2/27/2011

A sort of side note....

I've been sharing some of what we found on levnet, and when posting about Lev's oscillator, I missed putting a space between "Termen" and "oscillator".

The ever brilliant Chobbs caught this and called it "The Termenator"

That name will be proudly emblazoned on the instrument I build.

Thanks, pal...Rob.

Posted: 10/5/2012 1:33:26 AM
Amethyste

From: In between the Pitch and Volume hand ~ New England

Joined: 12/17/2010

I want one too... please :)

 

Posted: 10/5/2012 3:05:09 AM
w0ttm

From: Small town Missouri on Rt 66

Joined: 2/27/2011

Amey, that's a promise :)

Left handed, of course.

Posted: 10/5/2012 8:17:29 AM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

Been here before -

Folks, Please dont get too excited - dont set your expectations high, dont think the process can be rushed..

All that has happenned so far is that:

(1) A clearer understanding of the RCA's operation has been gained by me and some others, and the exploration is continuing.

(2) A Simulation of a fet based oscillator has been run, with interesting results, and a fet mixer has been designed and simulated..

The above DOES NOT prove ANYTHING! - We do not know how close either of the above modules are to producing the sound of an RCA.

I believe we WILL get there.. But I think we may have gone only about 5% of the way on this journey -

I really dont want to see something "come to market" which claims to be a "RCA Clone" design, but isnt.. As it stands now, the fet designs produced to date could probably be part of a reasonable starter theremin - but to get a true RCA "sound and feel" alike is going to take a LOT more work!

Fred

 

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