The Theremin Temple

I have not exposed myself in a while as I am unable to play a tune but I recorded this just now because she (enigma) had something to say.

Temple Spirits .mp3 210k

Perfect pitch field linearity has 900,000 reasons that it should not work and yet it does and a theremin voice has more reasons not to sound musical.

This is raw transistor with no acoustic enhancements like a microphone & speaker combo. Theremin direct to sound card. I think I have texture as I call it.

It may have noise which I can't hear cause I got wires running where they should not.

Christopher

RS,

I was a bit disconcerted by the ghostly "wheezing" sounds and other artifacts on the recording that, for me, interfered with the listening experience. 

Chris,

To me, the most interesting sounds were at the bass end - and unfortunately obscured by occasional bursts of something quite unpleasant.. The higher frequency sounds were, well, not particularly interesting or exceptional IMO - sine waves with some 2nd harmonics mainly.. But at the bass end there were both odd and even harmonics definately present - sounded a bit like a ramp waveform into a LPF.

The laptop I listened to this on has a fairly naff soundcard, and doesnt have my 'scope and spectrum analysis software on it either - to be honest, I never heard the "wheezing" peter mentions - sure I will get a better listen when I get to my lab and play the sample through my Tannoys.. Can also have a look at the waveform then.

But there was some really horrible loud artifacts which will prevent me from cranking the volume up loud !

Some info would be useful : What sort of mixer are you using ? (It sounds like a diode mixer with a too-big filter capacitor to me) and what frequency is your oscillator (aprox) ?

The "bursts" I heard and the "wheezing" Peter heard makes me think that you are failing to filter all the HF before it gets to your sound card - You REALLY need to get a good filter to eliminate everything lower than 40kHz before it gets to your soundcard - this needs to be right at the input to your card, so that HF doesnt get induced after the filter .. And also.. Put a 100pF capacitor into your plug or input socket, between signal and ground, for all channels...

IMO, (after the last time we explored the causes of the strange anomolies in you sounds, and determined that your sound-card was creating them) no "sound bite" you present can be "trusted" unless you make absolutely sure NO HF is getting into your card!

Fred.

Temple Spirits =  Ghostly Wheezing

I have always used single diode detection because I am not wise enough to know why not. I had a builder suggest using a shottky diode for this detection but I did not know why anything would change. Have them though.

The above sound byte was redone with careful observation of the oscilloscope and a spread out in Audacity. Before I had high impedance loose wires adding noise. Plus the computer needed a restart to free up system overloading. 100%

There is no RF in the audio and a nice mix of overtones.

100 Hz to 1150 Hz

I have found that putting field tension between the coils what ever that is, my lingo or feedback tension can add something but usually things get unstable.

My interest is a reproducible sound which this is.

Christopher

That new MP3 is much better - certainly better on my crap laptop anyway! ;-)

But more has changed than just a "cleanup" I think !  - higher frequencies now seem to have more harmonic content - (nice harmonics, IMO) - and I am sure the waveform (whatever it is) has a good spattering of both odd and even harmonics - I suspect a damped ramp type waveform.

On my lo-fi laptop, this sounds like a good basic waveform.. give it a bit of acoustic mudulation and you might even get it to sound like a Melodia ;-) -- Some "space blanket" stuck to your antenna, flapping about under the influence of loud audio might do the trick!

;-)

Fred.

ps - I should just mention that I discovered the connection between my laptop and the small external speakers waas a bit dodgy - it could be that the loud artifacts I heard on the original MP3 were a result of this.. whatever - they aint there now..

Fred said: "On my lo-fi laptop, this sounds like a good basic waveform.. give it a bit of acoustic modulation and you might even get it to sound like a Melodia ;-) -- Some "space blanket" stuck to your antenna, flapping about under the influence of loud audio might do the trick!"

Melodia? I want to sound like me. lol

In RF heterodyning it took me years to get a good sine wave which can then be tilted into a good ramp. I remember Theremaniac and Dominik were able to do this and mine was always hit and miss. For a newbie this must be considered a dark art as there is a balance and a light tickle, that must occur. I often thought of theremin circuitry and response as a Wheatstone bridge, doesn't really relate or does it?

To me the above sound byte sounds like the sadness in New Orleans today, I think enigma wanted me to express this.

My funny antenna can be a spring reverb inducing FM but I usually try and avoid that. That will be an experiment for someone else.

Christopher

Edit:  just made another byte called Spacial Sound .mp3  200k  Might not be as dry a normal transistor tone.

It may have noise as it is on the edge using Fred's FM feedback I believe, I call it feedback tension where by the audio re modulates the transistor base of the pitch oscillator. I think FM & AM are both introduced. Don't try this at home unless you live on the edge. The Null point does its own little beat so I stayed above it. lol

"The above sound byte was redone"  - RS Theremin

I'm hearing aliasing.  It's likely the anti-aliasing filter at the input of your soundcard isn't up to snuff, or you're pouring some intense HF at it (most likely both).

aliasing  (ā'lē-ə-sĭng)

1. Jagged distortions in curves and diagonal lines in computer graphics caused by limited or diminished screen resolution. Compare antialiasing.

2. Distortion in a reproduced sound wave caused by a low sampling rate during the recording of the sound signal as digital information.
   

Thanks dew, had to look that word up as I am not a musician. Well I can't see it on the scope or in an Audacity spread. Not only can I not play a tune I will never know when I have a good sound, you're all gifted.

The addiction will keep me moving forward. One day the right person will email me and the magic will be released!

My computer is ten years old 2.53 Ghz with XP 1 Gig ram. Wonder what I should buy?

Christopher

"aliasing  (ā'lē-ə-sĭng)
"

Ok - dont worry too much about the word.. you are not a scientist (sorry, but I disagree with Dewster on this - I do not think that one is a scientist automatically if one fiddles about with technology - That either makes you a user of technology, or a technologist / technician, or at best an engineer)..

Think of the word as a bit like the process you know - the process of two oscillators being mixed, and producing frequencies which are different to frequencies contained in the 'original' signals... No, this isnt what is REALLY happening, but its a workable fiction/factoid if one doesnt try to go to deep.

Changing your PC wont solve anything in its own right - except that a new PC MIGHT have a sound card with better filtering.

A far more reliable "fix" would probably be to get a USB "sound dongle" and build a small metal box (iron is best) which has enough space in it to house the usb "card" and a few components.

You want to bring the USB cable into the box, and you want a ferrite filter of some sort on this cable - You want sockets im the box for input / output of audio...

Take the audio from the sockets into a low pass filter with a sharp roll-off which starts at no higher than 20kHz - you want to attenuate all frequencies above 20kHz as much as possible.. You can buy filters specifically for this kind of application.. I suggest putting several of these in series to really squash the HF end, even if this means that audio signals above 15kHZ suffer some attenuation.

Take the output from the filter/s directly to the soundcard using as short a connection as possible.

The higher the sampling rate of your sound card, the better.. But increasing the sampling rate alone will not fix the problems - remember, a 96kHz sampling rate will produce aliasing with a 97kHz signal - think of them as a 96kHz "reference" oscillator beating with a 97kHz VFO - every signal and harmonic above 1/2 the sampling frequency has the potential to cause trouble.

Ground your metal box, and with filters and soundcard inside the box, and data transferred digitally between the box and the PC, the situation should improve greatly.

Fred,

Fred said: "A far more reliable "fix" would probably be to get a USB "sound dongle" and build a small metal box (iron is best) which has enough space in it to house the usb "card" and a few components."

Hi Fred and dewster,

At this stage of the game I am old and tired of soldering. Can you give me the name of a product and even an upgraded sound card? I now use RocketFish 5.1 without using their cheap Fx.

If you recommend something high end maybe I could transfer this to my new computer. I really want to get away from my box to a large laptop so I am portable.

Though I live on Social Security (just love the USA) cost is not an issue. Most of my work including hardware I buy is given away. <= To who you might ask? LOL

I would buy my student a Millennia STT-1 if I could compare a theremin before and after sound sample.

Thanks "everyone" on this thread as this has been positive feedback.

Christopher

Edit: I just checked my audio signal at 1 volt p-p and the RF on the audio line at 25 micro-volts p-p. Signal to noise I think is very low?