> I know I can use a pic with an A/D for measuring a voltage
> but how would you have a pic generate a frequency?

Use a timer interrupt. There is code at www.piclist.com for
setting the interrupt period. If you can generate a triangle wave
with a D/A, this circuit

http://home.clear.net.nz/pages/joecolquitt/tri2sine.html

will convert it to a pretty good sine wave. You can send this to
the audio amp to drive the speaker

I hoped to follow up on using a PIC pin a voltage source, which
would have been handy for the +/-12 and -5 needed (in this and
other analogue circuits), but perhaps you can derive them from
your amp PSU unless you already have a suitable one

> The frequencies needed are in the audio range from 1hz to about
> 20khz.

20kHz is OK, that's 250 instructions/hertz (at 20MHz) to approximate
a triangle wave

> If it hasn't been done already I have a schematic of the manual
> test setup using a freq generator and dvm to do the test manually.
> I could scan and send the schematic if anyone is interested

You could host it on your own page at PIClist, one of the admin
can help you do that

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