Made another drawing:
Mind you all, this circuit has not yet been tested!
Some things that might need looking after are the resistors R5 and R6 for instance, these might need to have a bit different value, maybe they are not needed at all.... The point of them is to keep the transistors in a state they are supposed to have when there is not current supplied to their base. Some transistors can go in a sort of limbo state, or even are latching (keep the state they last have been actively put in)
You may prefer using little mosfets like 2N7000 series as these have better base (gate) to collector/emitter (drain/source) isolation. I'd say first put it all on a breadboard to see if/how it works and then place it on a perf board or something...
These circuits are very basic rugged and yet effective discrete delays etc. based upon very basic NPN transistors. Many other kinds of NPN transistors will work just as well. The circuit will also basically work on any of the amplifiers as long as you keep an eye on the operating voltage. Delays can also be adapted by either increasing the C values or decreasing/increasing R values.
On other amplifiers pins may have other names, I name HMUTE before, but the TA2020 doesn't have that pin, it uses the FAULT pin for just about the same logic function (protection or fault indication purposes)
Good luck and if you have any questions just ask!
Last edited by V-bro; 04-Aug-12 at 11:52.
Pics can help a lot to diagnose something from any place on the globe...