ok - we now know its an XOR (Logic) mixer, and therefore know that this "soft" waveform is the core waveform.
I could well be wrong, but I suspect that there isnt a true VCA in this theremin - Having two VCA's in a low cost theremin did seem a bit unlikely to me (and having two independent waveforms out each being controlled by the same volume CV would require 2 VCA's) .. I suspect that the PWM from the XOR and other logic (to produce the "harsh" waveform PWM) are switching a couple of CMOS transmission gates (4066) or changeover transmission gates (4053) which are being fed the volume CV prior to integration / filtering.
[Edit] -> Just seen that both VCA and VCF are said to be in the box - Sorry, but I find it hard to believe there's a VCF in there.
It really wouldnt surprise me if a simplified version of the scheme I presented here and on Element 14 has been employed.
All fine and good - but if the above is true, then IMO its really sad - because with the addition of one potentiometer and a few cheap components, the "harsh" waveform could have been fully adjustable from triangle to ramp - giving a huge tone palette.
[Edit] -> It looks like there is a tone adjusting preset that does just that! ;-)
The critical test (possible volume interaction) and the fear that there may be problems in this area, have not been cleared away with these samples.
So until assec has more time and can deal with the matters raised in this thread, I would be extremely cautious before risking buying this theremin.
Fred.
Have linked the following to make life easier ...
more technical informations bellow:
http://assec.pl/details.gif
http://assec.pl/pureout.jpg
http://assec.pl/harshout.jpg
mp3 samples (direct from nano theremin output):
http://assec.pl/pureout.mp3
http://assec.pl/harshout.mp3