super nice transconductance amplifiers

[POLARIS at VAX1.Mankato.MSUS.EDU]

{I presume a lot of people are familiar with the CA3080,CA3060 and the
LM13700/LM13600.  Does anyone know of any OTA's that have GOOD signal
to noise and have linearizing diodes like the 13700's?}

Midwest Analog Products (http://Prairie.Lakes.com/~map/compons.html#quick)
is selling SSM2024 quad VCA chips.


Also, has anyone tried using 4-quadrant multipliers?  I just got some
Analog Devices 633JN low-cost multipliers ($6.20), and they couldn't
be simpler to use - they have two differential multiplication inputs,
plus a summing input.  The chip can run off of standard +/-15V supplies,
and can do multiplication, division, squaring, and square root.  I used
one with a joystick as a modulation controller.  When the pot is centered,
there is zero volts to the multiplier (which has the LFO as its other
input).  When you bend the pot up, you get positive LFO depth, when you
bend down, you get negative LFO depth (inverted polarity).  This is good
for unipolar LFO's, where positive waveforms bend pitch only upward, as
is the case with string vibrato, and negative LFO's take the pitch 
downward.  With the 4-quadrant multiplier, you can have either depending
on which direction the pot goes from zero.  The 633 also makes a nice
ring mod, BTW


Dave