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On behalf of ExpertVillage.com my name is Mark, and we’re going to talk about What
makes a Theremin sound special? Something discussed very little in the Theremin circles
is what makes the sound special. What we hear is it’s the tubes; it’s the transistors,
it’s this and that. What is the physical wave shape? Now if we listen to different
sounds that are produced by different wave shapes we can here a distinct difference.
A square wave will give a real raspy, buzzy sound, almost brassish. A flute will give
a pretty much a sign wave that’s a fairly pure sound without harmonics. A triangle wave
will give us a little bit of a stringed instrument sound. Well which one is a Theremin wave?
The traditional Theremin was made by beating two frequencies together and we ended up with
a signal that looked like an AM modulated signal, which is exactly what it is. Where
we have the carrier frequency in the middle and in the outer is the modulated audio signal.
Now when we detect that signal through the 6H6 dual diode what we get out of it is half
of a sign wave. What we do is remove the bottom half, so now we have what looks like the four
humps, but we still have the radio frequency signal in between. So we filter that out and
we get a signal that is a full, rectified sign wave or a full wave haversign that is
a Theremin wave form. Now the circuitry can do a little bit of clipping, distortion that
would give it a little bit more of whatever characteristics desired, but this is a true
Theremin sound.