[quote=“Obelixx”]
As the FM-modul KST-MW004 offers Stereo, it would be great that there would be a notice in the assembly instruction how to upgrade it to stereo.[/quote]
Seems to me, if you copy the circuit of the left channel and connect it to the right channel out of the module you get stereo.
See pin 8 of FM module marked L-out on the diagram. Connect your copied circuit to Pin 7 marked R-out.
Don’t know if you have to tell the FM module to switch to stereo, as this would require to reprogram the PIC.
About the min and max voltage see datasheet of LM386, this seems to be the critical part since all other parts run of the stabilized 5V, the LM386 runs of stabilized input that means in case of 9V battery minus Diode voltage drop a voltage of about 8.4V.
Depending on the Model LM386(N) it’s capable of running on a range from about 5V through 12V. Note that if running from 12V the ua78L05 will get hot as it has to dissipate the 7V difference between 12V supply and the wanted 5V output.
If you decide to run on minimum(e.g. 5V) you must omit ua78L05 and you could run it from for instance USB.
On a side note: wanted to buy one of these kits myself; seems better to buy two… and experiment a bit.
Hope this helps.
Greetz Deekay