How much does the amp/speaker/post-processing affect the sound compared to the waveshape?
Is it all about the harmonic content? If so how much room is there for achieving musical sound if harmonic content differs to professional devices?
How much does a good player affect the musicality of the sound? Even a bad piano player is clearly making music but it seems easy to make noise with the theremin - perhaps because there are not discrete notes but a continuous spectrum of pitches.
How much does the amp/speaker/post-processing affect the sound compared to the waveshape?Is it all about the harmonic content?
If so how much room is there for achieving musical sound if harmonic content differs to professional devices?
How much does a good player affect the musicality of the sound?
Even a bad piano player is clearly making music but it seems easy to make noise with the theremin - perhaps because there are not discrete notes but a continuous spectrum of pitches.
As to the first question, it depends, in a flat response amp & speaker (acoustic guitar or keyboard combo, PA, powered monitor), and with no or little effects processing in between, the waveform and brightness control on the theremin will for the most determine the sound. Instrument amplifiers, speaker cabs and combos that more impose their own coloring on the sound (guitar/bassguitar amps), and when you use the tone controls/equaliser on a flat response system will contribute, and contribute more to the voice when the frequency response differs more from a flat response. With effect pedals and modelers there is a range of possibilies from subtely modifying the sound to extreme changes.
The harmonics and their ratios to the fundamental tone is what make up a timbre/voice.
The player totally affects the musicality and with the theremin more perhaps so than with many other instruments.
I do think that to a certain extent something of a players sound is in the hands and in the individually unique ways of movements, timing, subconcious micro-movents, and how the dynamics of playing also contribute to the shaping of the waveform. Two different thereminsts could play a certain theremin with the same basic settings and still sound distinctly different in many ways.
The space control touchless interface poses special challenges, having to tangible or visual clues, it all depends on the developement of free/dynamic proprioception to get to the point of being transparent and it becoming more like singing after a lot of practice and then some more...
I had to chuckle how Dorit Chrysler said it in het presentation on the Amsterdam Dance Event, that the theremin is remarkable in how easy it is to make it sound terrible. 
Can someone diagnose all the reasons this:
https://soundcloud.com/adenf/pitch-and-volume-variations/s-ZMGjMv6565I
doesn't sound like this:
http://www.oldtemecula.com/theremin/tw/ews-enhancer-mic.wav
One sounds whinny and like a whistle while the other sounds full.
innominata, it sounds to me like the output is being clipped, with very little bass, and that the pitch field is erratic, entering the null point quite a bit. It also sounds like the volume field is more or less on / off, with no middle ground.
"That is why most digital designs prefer the basic sine wave whistle." - oldtemecula
That's total BS.
You make an interesting point with clipping. I assumed the speaker struggled to output bass because of the equal loudness contour so I increased the amplitude at the lower frequencies by amplifying voltage. If the clipping being heard is due to this then it would be better if I did the opposite. Why wiuld the speaker cause the signal to clip though?
The pitch field is good when a speaker isn't connected. See, https://youtu.be/yhNB3Lm3AC4
Here I can control the lowest tones pretty precisely.
It may be the speaker can't output low tones or it may be the speaker being a magnet is interrupting the whole circuits operation.
The volume range is imperceptible at higher frequencies but apparent at the lower frequencies, the high null point masks this and makes it appear as though the control voltage isn't changing much at all.
"I assumed the speaker struggled to output bass because of the equal loudness contour so I increased the amplitude at the lower frequencies by amplifying voltage. If the clipping being heard is due to this then it would be better if I did the opposite. Why wiuld the speaker cause the signal to clip though?" - innominata
It probably needs an amplifier between the Theremin and the speaker.
The signal shown in the YT video works well for a clean audio signal, because of the clipped sinusoidal or impulse form here with many overtones. The other soundcloud sample with volume control is completely distorted, a proper signal-to-noise ratio cannot be seen. I suppose, the problem is rather within the volume control unit. Which circuit is used?
The signal shown in the YT video works well for a clean audio signal, because of the clipped sinusoidal or impulse form here with many overtones. The other soundcloud sample with volume control is completely distorted, a proper signal-to-noise ratio cannot be seen. I suppose, the problem is rather within the volume control unit. Which circuit is used?
How look this signals before and after the volume control, measured with the oscilloscope?
It definitely gets more squared at the lower tones but honestly I don't think it's the VCA because using the spectroid app I was able to look at the frequencies coming out of my speaker and the entire 0-500Hz range is missing. When the waveform pitch is at the lowest frequencies eg 0-200Hz, the speakers output in the 2kHz range more than in the lower range - seriously!
This is a video of what the VCA does, basically exactly what I expect. https://youtu.be/hXPcDzrCX2s
There is a slight problem in that the 0-300Hz signals have a more squared shape, one would then conclude that the following is happening:
1. VCA introduces distortion on lower frequencies
2. Frequency spectrum of lower frequencies, due to distortion, have introduced high frequencies components
Therefore VCA induced clipping, case closed.
HOWEVER
Linear signals and systems tells us a square wave is made of series of higher frequency components with falling amplitudes, the characteristic frequency is always the highest.The high frequency overtones should have a lower magnitude than the low frequency characteristic frequency so VCA distortion doesn't explain to me why high frequency components are heard over the low frequency components.
If you remove the VCA altogether and throw the signal into the speaker you get similar but less buzzy sound behaviour.
My own conclusion are:
1. The VCA is introducing coupling because it gets its power rails from the voltage source before regulation. Why would that cause coupling? I don't know but it explains the low frequency shape change - but nothing else.
2. The bass dropout is entirely due to the speakers used. Bass dropout is also causing the theremin as a whole to sound whiny.
If the circuit can be adjusted to allow direct speaker drive with some trash like this then great: https://www.jaycar.com.au/76mm-all-purpose-replacement-speaker/p/AS3006
If it can't then I'll have to return to the speaker issue when I have better audio equipment.
You must be logged in to post a reply. Please log in or register for a new account.
