Quote Originally Posted by Luciano
Hi,

If you are interested, I can post a circuit
based on the TBA820M audio amplifier.
You can use this circuit for the headset tester.

IC TBA820M (8-DIP).
Digi-Key Part Number: 497-3025-5-ND
Price: USD 1.35

Circuit description:

Input: Electret microphone. (Phantom powered).
Output: 4 to 600 ohm.

Used components:

One IC TBA820M
One 9V battery
One on-off switch
Six resistors
Seven capacitors

* * *

Let me know and I will post the schematic of the circuit.

Best regards,

Luciano

I grabbed the datasheet. I'll see what happens.
JDG