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  • Theremin World - ChrisC
    for Builders Store Theremins and Kits Theremin Buyers Guide Recommended Effects Theremin Music Theremin Method Books Theremin Apps Accessories Theremin Books Logo Gear Auctions Forums Recent Posts Most Popular Topics All Forums search search ChrisC I m 55 years old Just fascinated with the ability to make sounds out of thin air About Location Hampshire UK Theremins 1 Moog Etherwave Standard plus ESPE01 Mk II upgrade module 2 UK designed

    Original URL path: http://www.thereminworld.com/user/ChrisC (2016-02-12)
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  • Theremin World - Topic: Let's Design and Build a (simple) Analog Theremin!
    are doing Simulation is rather different from what I m actually seeing voltage swings on the bench are lower with the base swing staying above ground LTSpice is here http www mediafire com download g8d3pq5accip5kt colpitts npn 2014 11 04 asc link Report Post Posted 11 5 2014 12 04 03 AM 4 dewster From Northern NJ USA Joined 2 17 2012 threads posts Exotic Oscillators Magic Antennas I m going to run counter to some thought here by stating my belief that there are no special oscillators out there with magical properties Oh sure you can stick an EQ coil on a parallel tank and generate all kinds of headaches along with some tunings that perhaps increase in linearity and or reduce sensitivity but in terms of single L oscillators they will all behave the same from a frequency deviation standpoint Lambda diodes push pull drive negative resistance quadrature sensing split tanks etc they re all the same in the pitch response department Some may play nicer with FETs or tubes or certain coils or give you nice things like high voltage swing or better absolute sensitivity deltaF deltaC and the like but that s it Similarly there is not a lot of difference in pitch response based on antenna geometry Make it 250mm long 500mm long it s going to have a little more or less capacitance but it s pretty much going to do the same thing and any linearity nonlinearity will still be pretty much the same Make it a spring and the capacitance will change a little when you stretch it In terms of absolute sensitivity the best antenna geometry is probably a small plate or petal shape livio pointed this out and I ve since done some rudimentary theoretical capacitive analysis of plates but most players are used to playing a rod which is probably more linear so here we are I state the above not to upset or inflame others but to spare beginners years of barking up fruitless trees Anyone finds an effect to the contrary I d be happy to listen but be prepared to describe it in terms that I can understand link Report Post Posted 11 5 2014 5 07 59 AM 5 xtheremin8 From zurich Joined 3 15 2014 threads posts dewster firstly thanks for starting it very good definitions of the goals it s like a back to basics i ll would like to follow this project like one who is complete new to the materia also to achieve a deeper understanding of simulation and construction of circuits but as a newt a not entirely wrong t h inker one get s quite confused when it comes to math physics and the basic electronics and the reading of electronic books is mostly dry as the sahara and not one ended up in a theremin as a first Spice user never did before and it s not the dreamer has awakened ohdear new to mac i think i ll have to download the mac version to follow through here but to have a go i tried a ipad version called multisim touch and spiced the oscillator above very easy to do like lego a bit i placed probes in the simulation on almost all possible points to measure voltages over a period of time pressed start and it seems to work all probes show voltage etc and on a diagram one can see how a wave starts to grow to a certain level didn t dig deeper but for a complete noob i need to know where is the oscillator output probing point and what should be expected a pb mark on further schematic would clear out all my questions i learn more by doing but i see my learning curve is steep so i try to keep my saucy nonsense by myself but hard trying to keep on tracks dewster you mentioned the use of plate antenna so why not use this for the volume side it s already aproved by them masters too technically and artistically link Report Post Posted 11 5 2014 3 43 06 PM 6 RoyP From Scotland Joined 9 27 2012 threads posts dewster thanks for generating this thread For me it is really interesting to see what thinking there is behind all of the stages required for a working theremin Afraid though that unless it is really a very simple problem then I m not going to be able to have much of a positive input into this project as my level of electronic knowledge is low albeit significantly more increased since I started looking into theremins Would it be fair to say that one would end up with a variant of the Melodia or Kustom design given that these seem to be pretty basic These seem to be pretty accessible constructions for beginners except the custom wound inductors Another thought or maybe the same one put in a different way given the aims of the qualities of this theremin starting from a ground up approach is it likely that what you d end up with is something pretty similar to the Melodia or Kustom link Report Post Posted 11 5 2014 4 19 05 PM 7 dewster From Northern NJ USA Joined 2 17 2012 threads posts xtheremin8 I m not sure if there are proprietary things going on with the LTSpice schematic files but I wouldn t be surprised PSpice in general uses a text based node and element list Were you able to open the LTSpice schematic in multisim touch or did you have to recreate it LTSpice is kind of clunky until you get used to it kind of reminds me of DOS or Win3 1 stuff But like everything I suppose once you use it enough it becomes second nature and it is free Output from the oscillator could be at the base or emitter of the transistor or even the collector if C4 is reduced

    Original URL path: http://www.thereminworld.com/Forums/T/30562/lets-design-and-build-a-simple-analog-theremin (2016-02-12)
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  • Theremin World - Topic: Antenna tuning.
    mixer circuit in between link Report Post Posted 4 28 2012 1 59 56 AM 3 nickexists From US Joined 8 17 2011 threads posts Ok thankyou Am I mistaken in thinking that the antenna capacitance and the antenna coils form a simple lowpass filter I have the circuit in a wood box so I ll try adding some more inductance Right now I have the antenna coils sitting beside eachother but still wired such that their magnetic fields will point the same way direction would it be better to have them all in a straight line The pitch oscillators are on opposite sides of the circuit board and I replaced the 330k resistors with 470k so hopefully coupling will be minimal Right now there is no antenna coil for the volume antenna and I would like to extend the sensitivity of the antenna can you recommend a good inductance value to place in series with a small 6 diameter circular antenna link Report Post Posted 4 28 2012 4 00 25 AM 4 nickexists From US Joined 8 17 2011 threads posts Nevermind about a coil for the volume antenna I fixed a bad connection and it works perfectly now link Report Post Posted 4 28 2012 4 04 16 AM 5 RS Theremin From 60 mi N of San Diego CA Joined 2 15 2005 threads posts Thierry said The principle is simple The coils in series with the pitch antenna and the static capacitance vs environment of the pitch antenna itself have to form a series resonant circuit which is tuned a little bit lower than the oscillator s parallel resonant tank circuit itself This is the first time you have made this comment worded this way did you discover something I am in total agreement with this aspect of your analysis Continue to take little steps and you might discover the rest of the story Why did you leave off the explanation of why the antenna circuit must be tuned below the edge of the oscillator freq How do you detect when this tuning relationship is on target Here is a non hack EWS 5 timbre fix that is so simple you could go to Radio Shack and have it working tonight Take the sharpness out of your theremin tone plus add two lower octaves this will create the illusion of better linearity Everything is simple once you have the answer I will leave it there link Report Post Posted 4 28 2012 2 14 45 PM 6 dewster From Northern NJ USA Joined 2 17 2012 threads posts nickexists thank you for the pointer to that construction article it s one I haven t seen before The author says this is a Colpitts and from the Wiki it appears to be a common base type but has some parallel capacitance across the coil which confuses me 1mH 680pF gives 193kHz I can t say I understand the 40mH total linearizing coil value This puts the

    Original URL path: http://www.thereminworld.com/Forums/T/28530/antenna-tuning (2016-02-12)
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  • Theremin World - nickexists
    Albums Theremin Videos Films Sounds and Audio Links Tech Schematics RCA Theremin Tech Keppinger Theremins Mods Software Resources for Builders Store Theremins and Kits Theremin Buyers Guide Recommended Effects Theremin Music Theremin Method Books Theremin Apps Accessories Theremin Books Logo Gear Auctions Forums Recent Posts Most Popular Topics All Forums search search nickexists About Location US Activity Joined Aug 17 2011 Last Seen May 10 2014 Forum Posts 25 Comments

    Original URL path: http://www.thereminworld.com/user/nickexists (2016-02-12)
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  • Theremin World - Topic: coil tuning
    with the fact that I always design with a view to production And the whole basis of DC control depends on the ferrite charactaristics And I cannot obtain the kind of technical data which gives me the assurance I need that these charactaristics are consistant The only way I will use staurable reactors is when I design the transformer myself and get it made But have been badly let down doing this Got a couple of perfect samples from China ordered production quantity these arrived and bore no resemblence to my samples Tiny changes in the linearizing coil will have much bigger effect IMO But I am not sure that there could be any problem with DC currents through this coil Perhaps at turn on for a few microseconds while the antenna is being charged but once this has occurred the antenna capacitance will be constant except for hand capacitance and no DC current will flow I suspect that the drift you are seeing may be more due to the active circuits power supply decoupling capacitors and semiconductor warm up than due to the inductors Fred Added In all my experiments circuits I use extremely stable band gap power supplies biasing oscillator transistors through the coils current is going to be dependent on the supply voltage therefore any variation in supply voltage due to temperature or whatever would change any DC offset current through the inductor resulting in drift link Report Post Posted 6 15 2012 2 01 56 PM 5 dewster From Northern NJ USA Joined 2 17 2012 threads posts And I cannot obtain the kind of technical data which gives me the assurance I need that these charactaristics are consistant FredM Yes tuning via saturation strikes me as being overly reliant on on ill specified parameters like BJT beta Tiny changes in the linearizing coil will have much bigger effect IMO But I am not sure that there could be any problem with DC currents through this coil Perhaps at turn on for a few microseconds while the antenna is being charged but once this has occurred the antenna capacitance will be constant except for hand capacitance and no DC current will flow I guess I was talking more about the amplitude of the AC voltage swing through the linearizing coil not any DC per se I suspect that the drift you are seeing may be more due to the active circuits power supply decoupling capacitors and semiconductor warm up than due to the inductors I suspect you re right The AFE relies on the CMOS threshold voltage to center and clip the LC sinewave Uh oh talk about design based on on ill specified parameters Surprisingly logic thresholds seem to be fairly steady things famous last words link Report Post Posted 6 16 2012 5 00 36 AM 6 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 threads posts Yes tuning via saturation strikes me as being overly reliant on on ill specified parameters like BJT beta Dewster Using a saturable transformer with a seperate winding for DC current to control the saturation one can simply use a variable current sink op amp BJT with emitter feedback ie voltage follower dumping current into fixed value resistor and getting this current through the collector which is connected to the control winding one can get precise control of saturation current The above works well My problem is that I cannot get data relating to the ferrites in the transformer Even when I specify the application and got samples made to my specifications there was huge variation between samples and production One can buy reactors but they are mostly for power circuits and they are all too expensive But I have found a few suppliers now who will make me some samples of what I want The reason I want to use this method is mainly for my voltage controlled heterodyning oscillators the object is to have a VC front end and implement a truly analogue register switching theremin But I also think there is a big application for these reactors in general theremins The best place to perform tuning is by changing the equalizer resonance Having a fixed reference oscillator and variable EQ inductance keeps the theremin tuned for optimum linearity The worst tuning method and most common is changing the reference oscillator frequency Reactors with several mH of DC controlled adjustment are quite possible and this also opens the possibility of having a MCU automatically calibrate for optimum linearity push a button put your hand where you want the null point and the control current is adjusted to set this null position whith optimum linearity regardless of the background capacitances etc Fred link Report Post Posted 6 16 2012 10 19 14 PM 7 dewster From Northern NJ USA Joined 2 17 2012 threads posts The best place to perform tuning is by changing the equalizer resonance FredM Sounds challenging When you say equalizer or EQ I assume you mean the linearizing coil Interesting way to tune a Theremin But wouldn t the tank resonance point as well as the fixed reference oscillator have to change too in order to preserve linearity link Report Post Posted 6 17 2012 2 05 06 AM 8 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 threads posts When you say equalizer or EQ I assume you mean the linearizing coil Dewster Yes I am talking about the linearizing coil or more generally about the series LC circuit which loads the variable oscillator But wouldn t the tank resonance point as well as the fixed reference oscillator have to change too in order to preserve linearity Dewster If one tunes the

    Original URL path: http://www.thereminworld.com/Forums/T/28592/coil-tuning (2016-02-12)
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  • Theremin World - Topic: Theremin and jazz?
    Drusilla of course will insist that it s a perfect fit because she wants to marry the prince Yes the theremin is a one trick pony but that trick is so spectacular and unique that it is quite magical when it is done well We do not do the theremin a favor trying to demonstrate its versatility by forcing it to do things it can t do On the contrary I think we do the theremin a disservice and end up marginalizing it even more than it already is LESS IS MORE I ve heard lots of theremin fans say that the theremin works beautifully in jazz but I have never heard a jazz fan say it link Report Post Posted 1 13 2012 2 09 42 PM 5 Amethyste From In between the Pitch and Volume hand New England Joined 12 17 2010 threads posts Peter you are a dream bubble popper lol But I do agree with you and clara that less is more That might be why the theremin somehow found me the genre i like to do is dream ambient and the theremin is perfect for this genre I do add some theremin to my music but I do it in a manner that is suiting to the theremin and doesn t sound like it is not blending at least i think I accomplish that If I cannot find the right effect or the results desired end up being not what I expected then I do not persue link Report Post Posted 1 13 2012 3 57 26 PM 6 Thomas Grillo From Jackson Mississippi Joined 8 13 2006 threads posts I think it s safer to say that not all jazz is playable on theremin If you ve not managed to master the art of crisp articulation then you re not going to be able to play medium rate jazz works I won t even think about the faster works I have found that if you avoid works like Dixieland and fast modern works you could actually do a decent job on the older slower works That s assuming you re having a go at works by 20th century artists works Copyright issues and not being able to afford licensures for all the stuff I d like to work with keep me limited to working on the works I ve been composing on my own or working with others on Keep it slow to medium and keep it within reason in the way of ability to tune with Some jazz works are so out there in the way of chord structures that it s impractical to add theremin to Not that I haven t at least explored it for my self I tend to stick to composing works that sound more like the slow to medium rate World War II era jazz I prefer more conventional chord structures which are more pleasing to the ear No not all jazz can be played on theremin but

    Original URL path: http://www.thereminworld.com/Forums/T/28437/theremin-and-jazz (2016-02-12)
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  • Theremin World - IanMcCormick
    Method Books Theremin Apps Accessories Theremin Books Logo Gear Auctions Forums Recent Posts Most Popular Topics All Forums search search IanMcCormick I work in therapeutic nonprofit and have worked with children adolescents and currently assist Veterans One of my hobbies is creating my own play therapy equipment and games to use with children Another of my hobbies is playing obscure board games I absolutely love the sounds of the Theremin

    Original URL path: http://www.thereminworld.com/user/IanMcCormick (2016-02-12)
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  • Theremin World - Topic: RCA THEREMIN
    Page 5 Page 5 of this topic link Report Post Posted 10 4 2012 3 19 13 PM 3 Chobbs From Brooklyn NY Joined 12 1 2009 threads posts from levnet today Rob and all What I was able to discern is that the RCA Termen designed oscillator is a modified Armstrong oscillator as you say But Termen took it a step further He biased the oscillator such as to not only oscillate at about 170 Khz but also pulsed like a blocking oscillator In effect he had two oscillators in one It is the supersonic frequency of the blocking oscillator about 20 Khz and its harmonics superimposed on the r f frequency that makes the sound unique at the mixer output I believe that Termen was influenced by the operation of the super regenerative detector which was an amplifier that also oscillated at a quench frequency of 20 Khz to achieve a higher gain Termen was not interested in the gain factor but the harmonics generated by pulsing the r f frequency for the harmonics that were generated Brilliant I would say so indeed Uncle Howie link Report Post Posted 10 4 2012 5 39 15 PM 4 Chobbs From Brooklyn NY Joined 12 1 2009 threads posts Also for further reference here is a clear and complete schematic of clara s theremin by Adrian Bontenbal he also built a Clara replica An evolved RCA the addition and location of variables pots and a cap are good indicators of where to tweak link Report Post Posted 10 4 2012 5 48 52 PM 5 w0ttm From Small town Missouri on Rt 66 Joined 2 27 2011 threads posts That explains the multiple resonance points Fred found Super regenerative design is not in my comfort zone Everything I ve played with has been superhet or direct conversion I did build a standard regenerative receiver once but it was a kit and I didn t take time to analyze it Time to hit the books link Report Post Posted 10 4 2012 6 05 40 PM 6 Thierry From Colmar France Joined 12 31 2007 threads posts I ve also studied the RCA and Rockmore theremin schematics for a long time thus it could be that Uncle Howie is right with his regenerative pulse theory but I am not at all sure about that And even if he is right I m mot sure about the post mixer effect of that I d really like to spend an afternoon with an oscilloscope and an RCA And I m still not convinced that it is possible to emulate the RCA sound with FETs and without audio transformers FETs act with a Uds Up as voltage controlled current sources as pentodes do But there are mostly triodes in the RCA which have a much greater output resistance which depends also on the plate voltage than any FET and thus behave more like voltage controlled resistors The mixer tetrode will behave in the same

    Original URL path: http://www.thereminworld.com/Forums/T/28796/rca-theremin (2016-02-12)
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