Analog Devices VCA ???

[R.G. Keen]

> I have not tried the 2018 in the panner mode so I can't offer 
> first hand experience. If you plot a graph of the outputs
> in this mode vs the control voltage it looks pretty wierd, due 
> to the (g-1) term.  To get an easy to use pan function you 
> would be much better off using two vca's with a control voltage 
> inverter.  I can't provide any "electronic images" at present 
> but if you want more info' I can mail a suitable control voltage 
> circuit to you.

I have designed control voltage generators, but thank you for offering
anyway. 

The 2018 appears to be the ideal voltage controlled panner, which is 
what I was really after. I've made dual control 13600 based panners,
and the inversion of control voltage complicates things a lot. This 
is actually going into a guitar effects pedal, and every additional
package drives the size of the box up. Worse, the volume range of
linear VCA's is not very pleasing, and the exponential characteristic
of the 2018 looked very good. I don't need the accuracy of a synth
vca, but I do need small, and powered by a 9V battery.

Are there any tricks to getting the thing to work well? The data sheet
mentions compensation often enough to make me think that the 2018 is 
prone to it. Is layout critical?

Is it fussy about power supplies? I intend to use a 
9V battery and invert it to give me +/- supplies in the 7 - 9VDC range,
and the supplies are usually not going to be symetrical. As a backup, 
I would go to 78L06/79L06 regulators, but that adds another $1 to the
cost, and another bit of circuit board to place, etc.

R.G.