Andrew wrote:

I did see the kit, but wanted to see if I could make something myself first.

There was a suggestion to us a microcontroller, and I am now considering the
use of the analogue comparator on an AVR microcontroller that will be being
used in the project.

It seems that most VOX circuits boil down to comparing a microphone voltage
to a threshold reference. I am not really to experienced in audio filtering
and amplification, so I would have to find some web documentation on making
a circuit to handle the sound in portion. I suppose it would even be
possible to have one of the PWM channels on the microcontorller set the
reference voltage, and in this way it would be adjustable.

If anyone has some tutorial sights on sound handling hardware (filter,
amplify, etc) please suggest.

cheers,
andy


A VOX is a simple circuit - no need for microcontrollers
or filters for a basic VOX. I made one with a 555 which
I triggered with a voltage created by the audio. Feed
the audio out of an amplifier to a diode & capacitor.
When there is an audio signal, the diode and capacitor
develop a voltage that triggers the 555. You don't need
a 555 - that's what I had on hand - you can use a
Schmidt trigger IC like a 4093.