Grounding

I have actually jumped while playing to see if taking myself off the earth completely would break the ground. Now, I understand why the theremin kept right on playing. My body really is the ground.

Here's another mystery that was answered recently. The space station makes electricity with solar panels, and stores the power in batteries. Equipment on the station needs a ground in order to work. If the station is in orbit, how is a ground established when it's haulin' tail around the earth at 17,000 miles an hour, and 200 miles up?

The answer is, they ground to the solar plasma which fills the entire solar system.

So, I'm guessing a theremin should work on an orbiting space station, airplane, or just about anywhere.

How big do you have to be to become a ground/earth?

If a very small person walkes by and not supposed to make an effect, how small does the person have to be?

If anything smaller, like for example a cat walkes close to the antenna what happends? How does the cat react?

I have to get a cat...

The capacitance of objects in the vicinity of the antennas modifies the resonance of the oscillators' tank circuits. Does not matter if the object is grounded -- if an object has capacitance, then it will effect the resonance of the circuit.

Small objects will effect the frequency however such objects must be close to, or touching the antennas. For example, once when rehearsing outside a June bug flew into the pitch antenna and during the split-second that it contacted the antenna the pitch changed drastically (an octave or more??) I wish I had a recording of it -- kind of a "zzzzzinnnggg" sound.

Now, the grounding of the theremin itself will have a pronounced effect on the pitch. And, yes... if the grounding is a problem, one can connect a wrist strap from a ground point on the theremin -- in effect, using one's body as a ground. This really doesn't effect one's body capacitance in any way that I've noticed.

How can you tell if there is a grounding issue? The easiest way is to touch a ground point on the theremin -- if the pitch jumps significantly then there is a grounding issue and you may have to resort to the wrist strap. The major symptom of a grounding issue is when a Theremin that normally tunes ok will not tune regardless of the setting of the pitch knob (that is, zero beat cannot be set).

Another solution to grounding problems, is to use a ground-lifter plug. One of those little adaptors that goes from 3 prongs to 2 prongs.

I was wondering what whould happen if a bug landed on the antenna.

Hum i didn't read it all (it is possible that somebody already mentionned this), but I remember that an artist used birds on stage with a wide range theremin, to make strange and random sounds, using the birds flying nearby the theremin, obviously without any contact with earth... I don't know if it's a legend or a show that really happened..

You can try with a bird you own... a bug would be too small I think...

As KKissinger mentioned, the bug is so small it would have to touch the antenna, or fly within a fraction of an inch to have any affect on pitch.

I've tried throwing small metal objects like a pencil, finger nail clipper, and a paper clip by the antenna while I was standing in the zero beat zone, and there was a noticable change in pitch as the objects flew by the antenna.

Now, here's the big question. I was standing within the control zone, and I'm grounded, so throwing something near the antenna while I'm standing near the instrument would be as if I'd moved my hand close to the antenna. True? False?

So, would there have been a change in pitch had nobody been near the theremin while an object was dropped, or propelled near the antenna?

Somone's going to have to try this in a very large room, becaues I've tried it in a 15 foot room, and did notice a change, but only when objects hit the antenna. I had to be near the antenna to notice a change when object passed near the antenna.

Tough question. Where's a good physicist when you need one.

[i]Another solution to grounding problems, is to use a ground-lifter plug. One of those little adaptors that goes from 3 prongs to 2 prongs.[/i]

The ground plug on a power cord is an important safety feature and I would recommend against the use of a 3-to-2 prong adapter.

Two particular grounding issues are important to electronic musicians. One is the issue of so-called "ground loops" that occur when multiple paths from a device to ground exist. The other issue is a faulty/non-existant ground connection.

The wrist-strap solution addresses the faulty/no-ground condition (as far as the theremin is concerned).

The ground-lifter solution addresses the ground loop condition -- however, a better (safer) solution would be to lift the ground from the audio patch cord rather than to lift the power cord's ground. A device such as the Ebtech hum eliminator is an effective tool to break ground loops.

The ground loop is created because the device (the theremin, for example) is grounded via the power cord's ground AND completes another ground connection via the shield on the audio patch cord.

If all the equipment (say, a theremin and its amplifier) are plugged into the same power source then there shouldn't be a ground loop problem. The problem occurs when the theremin is plugged into one power source and the amp is plugged into another. Though both devices are grounded, their paths to ground may have unequal resistance setting up symptoms of ground loops (60hz hum).

I have run into this issue with the Theremax -- for the Theremax uses a "wall wart" power supply and utilizes the audio cords shield as a ground connection. This arrangement has not always been successful for me and I have had better luck to lift the ground via the Ebtech device and, in turn, use the wrist strap as a ground point for the Theremax.

OK, why the safety concern? Well, electrical current always takes the path of least resistance. The case ground (that third ground lug) is there in case the device develops a short or problem that allows dangerous voltage levels to reach exposed case parts. Better for the voltage to pass through the ground lug than through your own body.

He's absolutely right! Forget what I said about the L-cheapo 3-2 adaptors. I'm getting some ebtechs ASAP, and tossing out the 3-2s.

Stupid me, we used those ebtechs when I was in commercial radio a quarter century ago. I forgot all about those things.

Thanks Kevin.