Open Theremin V3 sounds very weird

Hi all,

So I've built an Open Theremin V3.  I grounded it by making and wearing a copper wire "bracelet" and attaching alligator clips from the bracelet to the grounding pad of the theremin.  I then sat about 18 inches away, put my hands on my lap and ran the auto-calibration.

After doing all this, I recorded what my Open Theremin sounds like here:

https://soundcloud.com/desmond-rivet/open-theremin-range

If you listen, you can hear that the lower frequencies are very..."noisy"?  I don't really know how else to describe it. Basically, there seems to be a cutoff, roughly halfway through the physical playing field, where the sound will suddenly change in a very obvious way (it happens around 6s, 12s, 17s, 22s, 29s, 35s).

Admittedly, my speakers are very cheap, but this happens even on better speakers.

Is my theremin broken?  Could I have accidentally zapped it with static electricity?

Any insight is appreciated!  Thanks in advance.

Desmond

As you told, you are at lowest register. Your device should be able to produce some clean bass. 

The noisy part corresponds most probably to infra-bass lower end of the open theremin range. It sounds normal. 

Cutoff zone seems less normal.

Something is probably filtering lower notes somewhere between open theremin's output circuit and loud speaker.

Remains to understand what...

Hi,

I listened to the sound with better speakers and I played the same sound on my OTV3 to compare.

On mine, the "motor" sound in infra-bass is not so strong and I have a softer sound elsewhere.

You said in your other thread about calibration: "Everything is set to default. The register and timbre knobs are all the way to the left.  The volume and pitch knobs are at 12:00." I guess that you have not changed sample tables.

So, normally, you should also have a soft sound (close to a sine wave).  But your sound seem to have more harmonics compared to mine. 

The strange sound that you have could be due to some distortion. 

Remenber that output signal of the OTV3 is very strong. It could saturate amplifier input resulting in some added hamonics (richer sound).

The richer is the sound, the more clearly you will hear a "motor" sound in infra-bass (in fact you hear the higher harmonics).

The softer is the sound, less motor sound you will have in infra bass.

Maybe you could try to attenuate signal between OTV3 and amplifier (a 10K pot or a Volume pedal would do).

Thanks for the reply again.  I have updates.

I had forgotten that I had connected the theremin to the speakers via a ground loop isolator.  I removed that, and the result sounds like this (everything the same as before)

https://soundcloud.com/desmond-rivet/open-theremin-range-improved

That sounds much better, right?  Perhaps it's not broken after all. 

Thanks for all the help!

Desmond

Hi,

Yes, the sound seems correct now.

Enjoy your theremin !

Vincent