Hello "iz oos",
normally a vogad, such as the SL6270 or similar, is used as a dynamics compressor for microphone input, obviously, with the appropriate checks of in / out levels and coupling impedances, nothing prevents it from being used even in a BF circuit to control the level output in the speaker or headphones, I just wonder if it's worth it, the cost will certainly be higher than a coupled LED / photoresistor that can give equally valid if not better results.
The advantage of the audio compression system that gives an LED / photoresistor circuit is the flattening of the dynamics practically independent of the input frequency (obviously within the limits of the LED's ability to react to high frequencies) on a much greater frequency spectrum than a chip vogad, this allows to keep the frequency response of the BF amplifier circuit intact.
Also consider the simplicity of the circuit (see the two attached diagrams), to add a LED / photoresistor compressor in the ?BITX just insert the circuit between the output and the negative input of the LM386 and that's it.
Best wishes from IW4AJR Loris
