capacitance effects and philosophy

livio I need you to stay around as TW gets really stale without fresh blood.

Though analog, I have my own ideas I want to share with you over time, maybe I will move some of my other posts here.

I have mentioned the RF factor in the past as I believe hand capacitance describes the pitch field, but not all of what is going on. Oscillator loading also changes the Xc of the circuit though small, this affects linearity also. I have a perfectly linear pitch field but no one has mathematically figured out why.

It would be great to get back to the hobbyist enjoyment and perspective of the Theremin

dewster is on a mission, he must keep his focus that is what he was saying. He will chime in here.

11 meter antennas at 5/8 wave always fascinated me.

Christopher

Christopher, that's an interesting way to temperature compensate!

I swear the horizontal antenna is easier to play with human arm movement as it also eliminates right left drifting. I am working on a volume control right now so can't test but my guess is that horizontal will eliminate interference from side by side Theremins also. It is mystical I tell you! Ok maybe practical.

This is what will be tested by the PP recommended Thereminist in Los Angeles.

Christopher

I will use the neon globe 25kv as an interference noise source and measure the narrow off the tip end and broad field which a normal theremin pitch antenna is.

Fred the South Bank Art Centre event was a major accomplishment. It is well known the theremin invites those that accomplish things and the rest will have more reasons to fail than to succeed. You had sixteen times success and just as much STRESS. I can’t get one successful build completed as the theremin is a never ending project of evolution. It would be best to leave it there as in the path of my theremin is found EMpathy, a human trait.

Christopher

Edit: Now I am in detention or is it segregation? Theremin Classic vs. Theremin Faux

"I swear the horizontal antenna is easier to play with human arm movement as it also eliminates right left drifting."  - RS Theremin

I assume your horizontal pitch antenna is placed higher than the volume antenna?  It's interesting but I think it might be a tough sell, particularly to Thereminists who have spend years on their vertical antenna playing technique?  Due to livio's suggestion I'm currently looking into at a round plate for the pitch side which might be a bit less of a tough sell (but who knows).

On your web site you talk about keeping the power supply and other warm stuff away from your pitch side, which makes a lot of sense, but this can be quite limiting in terms of boxing the thing up in an enclosure and declaring victory.  I imagine the IF transformers you use for your oscillators are the most heat sensitive components in there due to the ferrite - have you tried/considered hand wound air coils?

"I can’t get one successful build completed as the theremin is a never ending project of evolution."  - RS Theremin

Amen brother!  ;-)

"...and since 2010 I have gone nowhere other than nowhere. - those lost months becoming lost years."  - FredM

I'm generally OK during the day, but I'm starting to get these nights were I lay there thinking "what in the hell am I doing with my life?!?"  I think a lot of it is not having a vacation for a couple of years, and the steady grind of trying to decrypt research paper fluff into working spreadsheets.  But it's happening more and more and it's not a pleasant feeling.

I guess my main fear is losing focus, momentum, and above all losing interest.  I'm hoping the Theremins I eventually make will be easier to play than say the EW, thus pulling me into that side of things more.  But I'm more at home on percussive polyphonic musical instruments like the guitar. 

That, and production tends to be no fun compared to the design / implementation wind up to it.  So the order of the day is: keep it simple to build, and stick it in an off-the-shelf enclosure.  Aim for being able to assemble one per day without automation.

~dew  (better copy this)   They let me out of detention so I could walk the prison grounds.

You are like the Anti-Theremin but these are really good questions I will answer for other theremin explorers.

My volume control can be placed anywhere, I prefer a sideways stance right arm to the pitch antenna and the volume control on the other side where my left arm is. The body is in between. Volume or pitch can be at any height relative to one another because of this setup.

My design can be played exactly like the RCA but sounds much better =>       Listen.mp3 460k

It's interesting but I think it might be a tough sell, particularly to Thereminists who have spend years on their vertical antenna playing technique? 

If a person needs a vertical rod to aim at, a plastic one can be stuck in the proper place. I have said many times there is no theremin market, I have nothing to sell, I give everything away. You owe me $50

Due to livio's suggestion I'm currently looking into at a round plate for the pitch side which might be a bit less of a tough sell (but who knows).

My volume antenna is a 4" long #26 gauge wire "only" which connects to the pcb. It's response is played in the one to two feet area above it with an analog tapered volume field with most response in the outside loud field and a wide shading window in the inside field. This is accomplished using primitive PWM.

On your web site you talk about keeping the power supply and other warm stuff away from your pitch side, which makes a lot of sense, but this can be quite limiting in terms of boxing the thing up in an enclosure and declaring victory. 

This is one reason my pcb snaps apart, the oscillator section can be in its own compartment with natural air.

I imagine the IF transformers you use for your oscillators are the most heat sensitive components in there due to the ferrite - have you tried/considered hand wound air coils?

~95% thermal drift comes from PN junctions. In dual LC oscillators the minimal coil characteristics cancel one another. My tube/valve design uses standard IFT coils with warm vacuum tubes nearby and it has "no" drift. I have only tested it over a 10 degree F window. My wanting to try the 100 uh chokes as coils is due to coil current concerns.

My present design, and there have been many, is with vacuum tubes in your famous 4 x 4 vinyl post open on both ends for ventilation. Volume and pitch enclosures are 24" long, mounted on a mic stand.

The final appearance of everything is a tall slender instrument with "no" antennas but played in a more ergonomically correct manner. My pitch field is linear right up next to the antenna, the Thereminist hand is rarely less than 10" from the antenna. Inside 10" is more for higher octave effects playing.

There are no exaggerations on my webpages just 10 years of hands on demonstrated research.

Christopher

"You owe me $50"  - RS Theremin

Can I pay you in bitcoins?

"In dual LC oscillators the minimal coil characteristics cancel one another."

No argument, just a comment that this works best when the magnetics of the two oscillators are somehow tightly thermally connected.

I hope you don't think I'm saying you're doing the wrong thing by using IF xfmrs.  It's just that air coils are super easy to wind and I'm wondering if you have experimented with them at all? 

dew said:

No argument, just a comment that this works best when the magnetics of the two oscillators are somehow tightly thermally connected.

Why would both coils not be at the same temperature?

I hope you don't think I'm saying you're doing the wrong thing by using IF xfmrs.

In practice I do not have any coil issues, my tube/valve theremin lights up the florescent tubes in my kitchen when switched on. (-' The tiny IFT have 5 ma dc passing though them. Lord knows what the oscillating current is.

It's just that air coils are super easy to wind and I'm wondering if you have experimented with them at all? 

You should know, I use to wind air core on pvc and found the 100 uh ferrite chokes used as coils made for a happier theremin. Every builder knows what an unhappy theremin sounds like. Also in analog theremins you want to shield the independent oscillators from sharing uncontrolled "EM" interference or you will get unwanted distortion in the audio waveform which is the very thing that allows an AM radio to work as a preview. This is why big coils are a disadvantage, the coils can talk too loud to one another through static and magnetic coupling. This is why some theremins shriek! This is a very difficult thing to over come once poorly designed.

Christopher

Edit: This is only one oscillator, the other coil is mounted a distance away. 30 gauge wire RS

Clamps at Lowes

Got my volume control back together, theremin has a deep throaty purr in the background, I am home again.

"Why would both coils not be at the same temperature?" - RS Theremin

There can be temperature differentials in anything, so unless you stick things together with thermal paste or similar you can't guarantee they'll be drifting the same way.  Though of course in practice they may be fine, particularly if you don't have them dissipating too much power or place them in a thermal gradient environment.

"This is why big coils are a disadvantage, the coils talk too loud to one another through static and magnetic coupling."

You could likely minimize this by splitting that coil into two equal turns windings, one wound CW, the other CCW, with some space between them on the same form.  You would need a bit more wire to do it, but not that much.  It looks like you are using a fairly hefty wire gauge.

Where did you get those pipe clamps?