[sdiy] THeremin - tweak C28 and C31

[Buck Buchanan]

> I feel compelled to dis this circuit every time it comes up since I
> bought one, built it, it worked like crap, I tweaked it like crazy, it
> still worked like crap, 

Hi all,

It's funny this topic should come up as I just finished my Theremax
based Theremin controller... at least the first stage of it.

I too was dismayed by certain areas of it's performance - WAY too much
cost reduction IMO.  However, especially if its purpose is to be used as
a synth controller only, I found that tweaking C28 (pitch side) and C31
(volume side) allows one to customize the antenna response (well, not
acutally but it has the *effect* of doing so).  It may have been
something to do with my case and antenna set (not stock) but I found the
volume CV output very nonlinear and didn't really work well until my
hand was close.  Very low diference frequencies weren't making as high a
CV I thought they should.  But making C28 = .0047uF and C31 = .0056uF
really improved response when further from the antenna.  My values for
these parts may be a little extreme (specially volume side) - your
milage may vary.  Either way, this gives the integrators something to
work with at low frequencies.

Oh, also, the tip from the Paia web page in increasing coupling between
sense and local oscillators seems to be a good one for the pitch side
especially. 

Take it easy,

buck