LM-380N-8 Audio Amplifier Stage
I started this project with a purchased module that had an integral volume control soldered to the board and had a threaded nut so that the assembly simply screwed on to the front panel. What I bought (regrettably too hurried before I clicked Buy It Now) had some TDA device that accepts a stereo input and provides a setero output.
It was like bringing a knife to a gunfight and was woefully underpowred and meant I likely would need a pre-amp stage ahead of it. So I just moved on and built a pre-amp stage and an output stage on a single board. It is now robust enough to amplify weak signals.
The Pre-Amp stage is the same design as the Microphone Amplifier (2N2222A) and the output stage is a LM-380N-8 which needs only three additional components; one 2.2 Ohm resistor and a two 220 Uf capacitors. That is it! The 10K volume control connects the Pre-Amp electronics with the LM380N-8 output stage.
Voltage is applied to Pin 7 via the 2.2 Ohm bypassed with the 220 Uf. The output is taken from Pin 6 via another 220 Uf. Pins 3, 4 and 5 are grounded and Pin 2 is the Input via the Center Wiper of the 10K pot. Pins 1 and 8 are NC. The Plus side of the 220 Uf output cap is connected to Pin 6 .
For those who don't read: THE SAME AMP IS USED FOR THE MIC AMP AS WELL AS THE AUDIO PRE-AMP ! The Plot Data for the 2N2222A is the same for either one.
I tested the Mic Amp in Transmit using audio tones at 200 Hz, 1000 Hz and 3000 Hz. The output is FLAT so your signal will have Presence!
You have heard how it sounds from some of the embedded you tube videos and this is a keeper module!