New Mixer Topology

RE: Reply to Dewster, and rant about sharing information, and othe OT matters:

"If anything, the mystery shrouding a somewhat different seeming product piques curiosity about how it works, so anything unusual will just get reverse engineered that much faster." - Dewster

Usually, this is how things work, I agree..

With theremins, it doesnt seem to work like this - there are too few of them, and too few people who have the knowledge and access that are willing to disclose what they discover.

We have the Tvox, the Evox, the 91 series, the E-Pro, the Henk's all shrouded in mystery - and there are probably others..

And there is a load of pressure on anyone in the "developers club" to keep the wraps on anything one finds out..  (or at least there was when I was part of this unofficial "group")

IMO, it is time for a new "breed" of "developer" - Time to open the cans and expose the contents - Theres no real money anywhere in this "industry" and theres no real "glory" or "esteem" to be found in it either.. But its such a small pond that even a small fish can have delusions of grandeur.

Lets face it - Compared to the technology most senior engineers deal with daily, even the most competent engineer in our "pool" is nothing "special" ... Perhaps (and I speak for myself here) this is one of the atractive things about this "pool" - One could quite quickly get elevated to the status of "worlds greatest authority" on theremin technology - but not stand a snowballs hope in hell of attaining any serious recognition in any other specialism in electronics.

No chance of money, no chance of real fame or recognition (even iof one did rise to the "status" of "worlds greatest authority on theremin technology" anyone attaining this status would, unless deluded, know it was almost worthless) - may as well just open it all up and let everyone share whatever we develop or discover!

Added ->

I think the truth about many "undisclosed" theremins is that their design is "uncomfortable" for theremin engineers - Many (if not all) are not "true" theremins, some of the best loved and most revered use "digital" technology even in their audio path, and others do not use any kind of heterodyning at all in the audio stage (even if they may use it to generate control voltages or signals).

The reality of these instruments flies in the face of the mythology generated by generations of engineers - and many (most ?) are extremely unhappy about the idea of this mythology getting busted.

Even great engineers were "tarred" with this IMO, Bob Moog was declaring that the theremin was "not a synthesiser" at about the time he was producing a theremin which was nothing but a voltage controlled analogue synthesiser!

The idea that there is something "mystical" embedded in the theremins heterodyning tone generation is really deeply pervasive - That somehow, waveforms produced by heterodyning are superior to identical waveforms produced through "synthesis" ... Despite rational evaluation, this idea is attractive and seductive - And it has held me in its grasp - even now, although the grasp has loosened, I can still feel it.

Fred.

THIS IDEA AND THE SCHEMATICS ETC RELATED TO IT ARE UNSUITABLE FOR ANYONE WHO DOES NOT UNDERSTAND SAMPLE AND HOLD CIRCUITS, AND FOR ANYONE NOT  ABOVE BASIC ELECTRONIC HOBBYIST LEVEL.. YOU CANNOT EXPECT TO JUST BUILD THESE CIRCUITS AND HAVE THEM WORK WITHOUT UNDERSTANDING THEM AND DOING THE REQUIRED ADAPTATIONS TO FIT THE APPLICATION! << This warning was added on 3/29/2013 1:18:28 AM >>

RE: REPLY TO RS : Note - IMO this posting has LOW INFORMATION CONTENT - People with technical understanding will most likely be wasting their time by reading this!

"The problem is to just talk about producing this sound and writing things most don't understand is not helpful to me."

Sorry, thats not my fault or my responsibility.

"Give me a sound sample I can view in software so I know what the end result is of what you are talking about. I can compare to my single diode method and maybe learn something."

The sound out / waveform out, from my full circuit, is simply the waveform of the oscillator being "sampled" - Therefore the possibilities are infinite. Even with the simple circuit shown, put a HF (VFO) square wave in, you get a square wave out at audio frequency, put a sine in - you get a sine out, put a ramp in - you get close to a ramp out, put a complex shape in - you get the same complex shape out with a bit of "smoothing".

You are obsessive about samples - particularly with regard to me! - It doesnt matter how often I state my position, you return to your "theme" like a stuck sampler! ... I could post a sample from this sampling "mixer" - But what point would there be ??? What could you learn from it if you dont understand that the sample I chose to create could be ANYTHING - ?

If you dont understand, you could sit with the most sophisticated audio analysis equipment for the next ten years and still have no clue about how the sound was produced, because the sound TELLS YOU NOTHING ABOUT HOW IT WAS PRODUCED !  ... A few words of plain low tech english and a schematic with 3 components tells you EVERYTHING about how this "mixer" works!!!!!!!! 

"You have to bring it down to the layman's level."

No I dont! - This is a technical theory forum - If I kept everything to a level you could understand I would need to write all day and fill TW with tutorials starting at how to count, and going through basic school level science and core electronics - I dont have the time.. And even if I did have the time and did all that, you still wouldnt understand, because YOU DONT WANT TO UNDERSTAND!

Provide me with a calibrated "layman" against which I can judge whether my postings are above or below "layman's level." And I will see what I can do to meet your requirements.. However, some of my postings will be above the level that non-technical people can fully grasp, this is a fact of life - Most postings in the TECHNICAL THEORY FORUM are likely to be MILES above your comprehension, its just a fact of life.

Fred.

YOU need to accept that we have a comprehension gulf which is impossible to overcome - I am NOT willing to spend my time explaining anything to you anymore, its just too much effort and I dont feel you are worthy of this effort.

It is best if you understand this and avoid wasting your time reading my postings - they are above your head - just accept that, and spend your time more usefully playing with your diodes!  

RE: Reply to RS : **OFF TOPIC - "NITPICKING"**

" As soon as everyone recognizes there no longer is, if ever, a market for the theremin, the nitpicking non-sense ends." - RS

No, it doesnt -

The issues which cause the "nitpicking" are rarely anything to do with the commercial viability or money.

The issues which cause the "trouble" are many, but are primarily based on ethics IMO, honesty, integrity, stupid insignificant matters like that ;-) !

Also, attitudes towards the importance of information and the harm mis-information can cause, attitudes about the advancement of technology, about education - all those kinds of things.

Attitudes towards disclosures which may enlighten people " I think a little secret is a good thing as I was afraid Thierry was going to reveal all." - You want people (including yourself!) to remain ignorant - The more ignorance there is, the easier it is for the ignorant to be taken seriously! - So ignorance suits you fine, and you fear any kind of real advance in understanding.

And there are also the personal aspects - personal likes and dislikes, "justified" or "unjustified".. There are issues about comprehension, there are educational differences, there is intellectual lazyness, there are political perspectives, there are issues of pride and trust and betrayal and confidence, there are people who are decietful and want to mislead others or pass off their rubbish by using someone elses good name, there are trolls and vandals.. There will always be  at least "nitpicking" - Sometimes this may be better than full-scale flame war though! 

Deciding what is "nitpicking" and what is "important" is itself a matter where "nitpicking" will occur - there is no way out - the only time it will end completely is when humanity is extinct (or if we survive long enough to grow up and are all capable of understanding simple things - and those who are not capable dont need to pretend in order to get respect or esteem or money - they are supported and valued for who they are, and all the motivators for "wrongness" are removed from our psyche, and a new "Jerusalem" descends from the skies and the lion and lamb share a bed and the angels sing accompanied by a theremin orchestra... ).

Fred.

RE: IS THIS SCHEME THE SAME AS USED IN DSO's ?

"Moreover, the same method (stroboscopic sampling) is widely used in DSOs to transfer GHz waveforms under Nyquist frequencies." - Ilya

Having now looked at sampling technology in GHZ oscilloscopes,I do not believe that the "stroboscopic sampling" employed in these is the same as what I am doing.

The major difference that I can see between "my" idea and sampling systems I have been able to find, is that "my" scheme uses the frequency / phase shift between the oscillators to determine the sampling point, wheras sampling 'scopes operating in the GHZ have a synchronised sampling delay which increments the sampling point across multiple samples..

The "sampling frequency" is not, AFAIKS, a GHZ signal close to the frequency being sampled, and therebye producing a difference waveform - I see no similarity in this technology to what I am doing.

"My" scheme  achieves the function required for (my) theremins - that of generating an output which is the sampled oscillators waveform "downshifted" to the difference frequency.

I have not (yet) found any publication where this scheme is presented, or anything that is similar.. This is not (IMO) too surprising - Generating a difference frequency having the waveshape of one of the oscillators is not something I can see any wide use for - In order to work, the two frequencies need to be quite close - it wont work if either input signal deviates from the other by much - and certainly not by more than an octave (this is talking about the input frequencies, not the downshifted output frequency - the downshifted frequency can span many octaves) and loses resolution the further the oscillator frequencies are apart, so is of no use for most applications (and certainly no use for sampling oscilloscopes I think!).

However, for theremin application, the above limitations are no problem - one has only a tiny difference in frequency between oscillators.. usually less than 2%.

This scheme is absolutely ideally suited to theremins, but it is doubtfull in my mind whether it would be much use for anything else.

Fred.

RE: DOES THE HENK THEREMIN USE THIS SAMPLING SCHEME ? :

"The idea of using a kind of switching demodulator in a theremin is not new. Anthony Henk did it already in 1994: the signal from the ref osc is fed (2.5Vpp DC free) into the drain of a 2N3819 FET which acts as a variable resistor/switch (no DC between drain and source, both on ground level). The variable osc's signal is clamped through a capacitor with a diode to be between -3V and +0.7V and fed into the gate. The FET's source goes to 2 RC low passes in series before another FET will amplify the resulting audio signal in a ordinary common source circuit. I think that in this configuration the source and drain pins of the switching FET could even be reversed without any impact on the principle of operation..." - Thierry

"The variable osc's signal is clamped through a capacitor with a diode to be between -3V and +0.7V and fed into the gate."

This, to me (unless the variable osc's signal is a square switching betweem -3V and +0.7V) sounds like the FET is operating, at least some of the time, as a voltage controlled resistor.

If the FET is operating as a VCR for any significant period, then the Henk mixer is, in fact, a fairly conventional multiplying mixer.. Its could be a really nice mixer - particularly if the FET pinches off and one gets the resultant harmonics from the non-linearities in that area.

Unless use is being made of the sampling possibilities presented by "my" scheme, even if the FET is being used as a switch, the full potential of the idea is not being exploited and probably hasnt been realized - what is being done is probably no more than other FET based mixers IMO.

For "my" scheme one needs as sharp and clean and short a sample as possible - A FET operating as a VCR and / or being closed for any significant period of time completely undermines the operation of my scheme - so I do not believe (based on information given to date) that the schemes / "mixers" are likely to be the same or performing the same function.

Fred.

"The only thing I'm slightly concerned about is some company like Bheringer taking one of my designs whole and making it for $100 retail or something.  But I have a feeling the Theremin market is too small for them to really care about it, which is one of its beauties, actually." - Dewster

Yeah - its such a small pond, theres no space for any big fish!  LOL ;-)

The bigger worry to me is developing something but not patenting or publishing the idea - just going into production... Then some competitor reverse-engineering what I have done, filing patents on my ideas, and preventing me from manufacturing my product..

Fred.

"Then some competitor reverse-engineering what I have done, filing patents on my ideas, and preventing me from manufacturing my product.."  - FredM

Lately the intellectual property system seems to be mainly used by big fish to extract / extort money from other big fish.  The man usually only gets interested when some rival gang on his turf starts horning in on his take of the action (too many parallels between capitalism and criminal mob behavior!).  

Not that it's any great shakes, but I want my stuff out there helping others if there's a chance of it doing so, and electronic copies of code don't cost me anything.  And I'm probably an idiot, but this is why I don't put any ownership, copyright, or disclaimer text in my files: I wrote it but I don't know how original it actually is, anyone that really wants to use it will do so regardless, and the more money / clout they have the less power I have to stop them - just about any company could easily outspend me in court, making any rights I might have to a design rather moot IMO.

If it actually does come down to an honest court battle, if you publish openly you have some proof that you thought of it first, or at least before they filed their patents.  Engineering notebooks could give you some cover too I suppose. 

But IANAL!

RE: HENK MIXER.. ANALYSIS:

Based on the little information I have from Thierry, I have thrown together a hypothetical circuit to "test" the likely mode of operation for this mixer.. My primary interest is whether this is likely to be behaving as a "sampler" or as a "mixer"..

The test circuit is shown below - values selected will affect the output waveforms, but, in my view, the mode of operation will be primarily determined by the signal presented on the Gate.

It is my conclusion that this mixer is acting like a synchronous heterodyning mixer and is not behaving like a sampler, it is, IMO, completely different to what I have done... But quite similar to what I started doing which led to my "real time sampling" mixer.

 I like this mixer - it has a lot of similarity to dual FET mixers I was playing with re the Lev Clone, but its even better due to the synchronous aspect.

Waveforms shown for both oscillators having 2.5V p-p amplitudes:

Waveforms for situation where reference amplitude is increased to 6V p-p .. This produces a harder turn-off.

Waveforms shown with reference amplitude reduced - Fet spending more time in its "resistive" mode.

The above, to me, clearly demonstrates that the two schemes are in no way similar in terms of the "sampling" operation ... It also however demonstrates what a nice little synchronous mixer can be constructed with a single Fet!

It needs to be understood that the wave shapes and amplitudes will depend on the component values and fet charactaristics - There is much that can be done to make this mixer much more versatile - for example, adjustable level and bias to the gate would allow the wave shape to be altered substantially.

Fred.

Reply to Dewster Re: PATENTS ETC:

"If it actually does come down to an honest court battle, if you publish openly you have some proof that you thought of it first, or at least before they filed their patents.  Engineering notebooks could give you some cover too I suppose. " - Dewster

Publishing is the only security other than patenting.. All other forms of "proof" are meaningless.. You can actually have a product in manufacture for 10 years, have design documents going back 10 years, even have published the design is some obscure public paper somewhere, and still have the rights taken by soneone else and be prevented from using your idea!

The only absolutely safe way to publish - a way free from any chance of argument, is to publish via your patent office... This gets your idea classified and put on record in a way which cannot be disputed.. You dont need to persue the patent - publication in this way costs you about £100 total if you are in the U.K.

The next best is to publish in a place recognised as a standard source of information related to the particular matter you are disclosing -

"an honest court battle" LOL ;-)  .. There aint no such animal ! ;-)

"You can actually have a product in manufacture for 10 years, have design documents going back 10 years, even have published the design is some obscure public paper somewhere, and still have the rights taken by soneone else and be prevented from using your idea!"  - FredM

Employers sometimes offer incentives to their employees to get them to patent things.  I believe the con game works like this: You get some pocket change for your idea, the company gets the patent, and when you move on you aren't free to use your own idea anymore.