Pitch Field Linearity II

Posted: 8/3/2020 4:48:23 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014


My observation in Analog Theremins is that ideal linearity is a natural tuning phenomenon in how radio frequency energy leaves the pitch antenna. Observing those neon plasma glass globes reveals exactly what is going on. Touch your finger to the globe is the same as touching the Pitch Antenna.


- Looks like Corona Virus -

Early on I referred to this as Radiation Resistance and it upset the digital people so I changed my term to Pitch Field Conductance. This is why playing bare foot or well earth grounded stretches the pitch field musical note spacing. The capacitive loop concept is cute but makes little sense. When you say no earth ground is necessary I do agree with you but for different reasons. RF will still find a way to escape the source controlled or not.

We talk about hand capacitance but the energy flowing in the pitch field is still RF something the digital people do not grasp so do not mention in conversation. RF is the elephant in the room along with the changing capacitive reactance of the tank circuit. Yes this change is extremely small but that is part of the theremin phenomenon.

Linear is the best word I know of for what we are talking in the musical note spread, it does not have to be perfect, Thereminist adapt. The goal after the ideal response is understood is that all theremins should one day have this same theremin pitch field response from model to model. This way muscle memory can be fine tuned which is what every Thereminist is searching for along with a better sound or even their own sound. It is better to demonstrate than throw around lame mathematical equations all day.

The Moog E-pro and the Becker Electrodeum meet this requirement. In my video this is why Master Thereminist Valery Shamarin of St Petersburg Russia adapted so quickly to the pitch field right out of the packing box.

Christopher   
www.Hwy79.com

The E-pro results arrived around the same time I also found them but we accomplished ideal Playable Pitch Fields using a different approach. Next to the antenna/electrode will always compress a bit, normal physics. Above G7 Classical Musicians do not care, only misinformed engineers.
.

Posted: 8/5/2020 10:27:10 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014


IMHO: In Analog Theremin design hand capacitance and earth ground has little effect on linearity as it stands on its own or separate as a tuned RF pitch/electrode.

In a tuned Pitch Antenna Electrode the voltage across the vertical design is distributed. At any given point the RF energy is a “fraction” of the total RF voltage. Un-tuned Pitch Antennas have the same total Pitch Oscillator developed voltage at any point on the vertical length rod. This overly pulls on the pitch oscillator capacitive reactance Xc in the near field.

Tuning the Pitch Oscillator slightly higher than the resonant frequency of the antenna circuit is where ideal linearity of the theremin circuit occurs. The Pitch Antenna circuit with inductors will have maximum energy here and it will be distributed energy. You tune the Pitch Oscillator above Antenna resonance because you do not want frequency crossover from the effects of hand capacitance. If cross-over happens the Pitch Field will have an obvious flat spot in the Pitch Field response.

On a tuned theremin pitch antenna hold your palm facing the antenna then bring your other hand up behind it. Now slide it to the side at the same distance and the so called capacitor plate is now twice as wide and the pitch frequency almost remains the same. Pop just a finger forward and the pitch goes up. There is a little more going on. If I say what it is now the TW monitor will get upset.

All future theremin designs need to take basic RF tuning into consideration, try a single coil and tune to that. Modern theremins should have similar Pitch Field responses between models, which is ideal.

Properly tuned Pitch Antennas allow the EtherWave Standard, the Moog E-pro and the Phoenix Electrodeum to have very similar ideal Pitch Field responses. Perfect linearity is not necessary as in any musical instrument rather needed is similar consistency between models in Pitch Field response.

Christopher


Posted: 8/6/2020 4:49:06 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014


The people that say the theremin responds to a magnetic field are just as correct as those that believe in the hand capacitance model.

If you tell people the same thing over and over it eventually becomes their religion if they know no better, whether it is true or not. They back up their belief with endless formulas or even Bible quotes. Some seek friends on social media that have the same belief to reinforce their own lack of common sense.

Hand Capacitance: The hand is not a metal plate, it does not have an alternating positive/negative charge on it and there is no mystical wire leading back to the theremin to complete the circuit.

What is actually going on is the electro-magnetic energy or RF emitted instantaneously from the Pitch Antenna circuit seeks the path of least resistance, just like the plasma globe and your finger. This has influence in shifting the capacitive reactance Xc of the variable Pitch Oscillator circuit. The Xc is the tuning capacitor referenced against another oscillator at the same frequency (heterodyning) that determines which musical note you hear. This is a very small change which the theremin concept is good at enhancing, a minuscule change of less than 1:100,000

Think of the energy around the Pitch Antenna as infinite rings of energy pushing out, where the circumference of the next ring out has less energy on the same line from the Pitch Antenna as it is expanded over a greater area than the inside ring. It is your finger reaching through these infinite rings that increases the current flow in the Pitch Antenna circuit which shifts the Xc of the Pitch oscillator, Xc is our mystery < 1pf variable capacitor.  An Xc change of just .888 pf is a sweep of over 7 musical octaves using a 330 uh inductor in the variable Pitch Oscillator LC at 900 kHz.

The higher the p-p voltage on the Pitch/Electrode Antenna the farther out the EMF is detectable. Use an analog AM Radio tuned to the Pitch Antenna frequency and listen to the heterodyned audio to know how far out you can in theory interact with the electro-magnetic field or RF of your theremin's Pitch Field. This can crudely work as a Pitch Preview.

Christopher

- This imaginary image shows why two hands side by side do not change the pitch much, yet a single finger forward is a new musical note -

Posted: 8/10/2020 3:45:35 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014


I have never been against digital vs analog, each has it's own proper application. Here is an outstanding digital approach released on video yesterday when the theremin does not meet your need. Digital can be really good but it will never touch what is naturally beautiful.

Peter Pringle brought this to our attention in LEVNET.

Christopher


Posted: 8/10/2020 5:56:38 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"Digital can be really good but it will never touch what is naturally beautiful."  - oldtemecula

I know you have an irrational loathing of all things digital (because you understand it even less than you do analog), but it's more the controller than the sound source here.  Keyboards don't have the expressive ability to do very many things well, and they particularly suck when coupled to continuous pitch instrument voices.  It's kind of too bad that piano type keyboards are the default synth input device.

Posted: 8/12/2020 3:57:32 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014


dewster you always follow my posts with nastiness and the "world is watching". You mention you do not like a limiting interface yet the keyboard works wonders on the piano. The bow on the cello sounds really nice while both are vibrating strings in a different way.

Drums or kazoos produce sound by a vibrating membrane, the pipe organ or oboe produce sound by vibrating columns of air. You have this notion you can improve the sound and response of bells & whistles if you could do them all hands free?  You are trying to fill a need that does not exist?

Have you ever got an unbiased outside opinion on your research? If all else fails and I know it is difficult, you need to take serious your mentioning Kruger and Dunning’s.

Christopher

Posted: 8/12/2020 7:22:16 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"dewster you always follow my posts with nastiness and the "world is watching"."  - oldtemecula

Just stating the facts.  You obviously hate digital sound synthesis, correct?  And Theremin fields clearly only consist of the "electro" (capacitive) portion of "electromagnetic" (RF).  Nothing personal, but the information in this thread is complete nonsense.

Posted: 8/13/2020 1:27:15 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"My observation in Analog Theremins is that ideal linearity is a natural tuning phenomenon in how radio frequency energy leaves the pitch antenna."  - oldtemecula

It's not RF, it's capacitive.

"Early on I referred to this as Radiation Resistance and it upset the digital people so I changed my term to Pitch Field Conductance. This is why playing bare foot or well earth grounded stretches the pitch field musical note spacing. The capacitive loop concept is cute but makes little sense. When you say no earth ground is necessary I do agree with you but for different reasons. RF will still find a way to escape the source controlled or not."

It's not RF.  Even when fully insulated, your body will always form one side of a capacitor with the universe.

"We talk about hand capacitance but the energy flowing in the pitch field is still RF something the digital people do not grasp so do not mention in conversation. RF is the elephant in the room along with the changing capacitive reactance of the tank circuit. Yes this change is extremely small but that is part of the theremin phenomenon."

It's not RF, it's capacitive.

"Linear is the best word I know of for what we are talking in the musical note spread, it does not have to be perfect, Thereminist adapt. The goal after the ideal response is understood is that all theremins should one day have this same theremin pitch field response from model to model. This way muscle memory can be fine tuned which is what every Thereminist is searching for along with a better sound or even their own sound. It is better to demonstrate than throw around lame mathematical equations all day."

Good musicians can adapt to anything, and there is a case to be made re. consistency, but whether the typical cramping of an analog Theremin is "ideal" or not is not demonstrated.  I personally find non-linearity to be a hindrance, and so a source of anxiety when playing.

"The E-pro results arrived around the same time I also found them but we accomplished ideal Playable Pitch Fields using a different approach."

There's only one approach and it's capacitive.

"Next to the antenna/electrode will always compress a bit, normal physics. Above G7 Classical Musicians do not care, only misinformed engineers."

Compression of the pitch field at the antenna is not a fait accompli.  My D-Lev is ruler flat all the way to the antenna, and this was accomplished via some fairly simple math and thoughtful engineering.  With the relaxed note spacing I prefer, it's easy to end up at the antenna when reaching for a high note, and other than my vibrato smacking the antenna it's no different than playing anywhere else in the field.

Posted: 8/13/2020 1:51:06 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"In Analog Theremin design hand capacitance and earth ground has little effect on linearity as it stands on its own or separate as a tuned RF pitch/electrode."  - oldtemecula

It's not RF, it's capacitive.  And every Thereminist knows that hand capacitance and earth ground have a huge effect on playability.

"In a tuned Pitch Antenna Electrode the voltage across the vertical design is distributed. At any given point the RF energy is a “fraction” of the total RF voltage. Un-tuned Pitch Antennas have the same total Pitch Oscillator developed voltage at any point on the vertical length rod. This overly pulls on the pitch oscillator capacitive reactance Xc in the near field."

It's not RF.  Xc is capacitive reactance.

"On a tuned theremin pitch antenna hold your palm facing the antenna then bring your other hand up behind it. Now slide it to the side at the same distance and the so called capacitor plate is now twice as wide and the pitch frequency almost remains the same. Pop just a finger forward and the pitch goes up."

The reason for this is capacitive.  Your hands are relatively far away from the antenna where intrinsic C dominates, so doubling the plate area doesn't have a lot of effect.  Moving a finger towards the antenna does because more field lines are able to terminate on the hand.

"All future theremin designs need to take basic RF tuning into consideration, try a single coil and tune to that. Modern theremins should have similar Pitch Field responses between models, which is ideal."

RF is only a factor for LC Q, which I believe is the limiting factor for antenna voltage swing, as well as environmental noise rejection.

"Properly tuned Pitch Antennas allow the EtherWave Standard, the Moog E-pro and the Phoenix Electrodeum to have very similar ideal Pitch Field responses. Perfect linearity is not necessary as in any musical instrument rather needed is similar consistency between models in Pitch Field response."

The Phoenix has an ordinary simple Theremin pitch field response.  The Moog Etherwave and Pro employ an EQ inductor, so they can achieve flatter pitch response at the antenna when properly tuned.

Posted: 8/13/2020 2:07:59 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"The people that say the theremin responds to a magnetic field are just as correct as those that believe in the hand capacitance model."  - oldtemecula

The fields are capacitive.

"If you tell people the same thing over and over it eventually becomes their religion if they know no better, whether it is true or not. They back up their belief with endless formulas or even Bible quotes. Some seek friends on social media that have the same belief to reinforce their own lack of common sense."

We're talking science here (well, at least I am) and there's only one reality.

"Hand Capacitance: The hand is not a metal plate, it does not have an alternating positive/negative charge on it and there is no mystical wire leading back to the theremin to complete the circuit."

The body is a big bag of salt water, so it is somewhat conductive, and standing on the ground forms a capacitor or resistor to ground, completing the capacitor if the Theremin is grounded.  The currents involved here are quite small and alternating at a sufficient rate, so the series impedance doesn't affect them much.

"What is actually going on is the electro-magnetic energy or RF emitted instantaneously from the Pitch Antenna circuit seeks the path of least resistance, just like the plasma globe and your finger. This has influence in shifting the capacitive reactance Xc of the variable Pitch Oscillator circuit. The Xc is the tuning capacitor referenced against another oscillator at the same frequency (heterodyning) that determines which musical note you hear. This is a very small change which the theremin concept is good at enhancing, a minuscule change of less than 1:100,000"

It's not RF, it's capacitive.

"Think of the energy around the Pitch Antenna as infinite rings of energy pushing out, where the circumference of the next ring out has less energy on the same line from the Pitch Antenna as it is expanded over a greater area than the inside ring. It is your finger reaching through these infinite rings that increases the current flow in the Pitch Antenna circuit which shifts the Xc of the Pitch oscillator, Xc is our mystery < 1pf variable capacitor.  An Xc change of just .888 pf is a sweep of over 7 musical octaves using a 330 uh inductor in the variable Pitch Oscillator LC at 900 kHz."

The energy isn't "pushing out" - it's an oscillating voltage field.  Xc isn't measured in Farads, it's an equivalent impedance measured in Ohms.

"The higher the p-p voltage on the Pitch/Electrode Antenna the farther out the EMF is detectable. Use an analog AM Radio tuned to the Pitch Antenna frequency and listen to the heterodyned audio to know how far out you can in theory interact with the electro-magnetic field or RF of your theremin's Pitch Field."

This is an SNR thing, a larger signal is detectable over a larger distance before it ends up in the noise.  And the signal is capacitive, not RF.

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