Low Noise Preamp
A low noise amp must be
constructed to reduce the amount of "hiss" that is generated by a
standard preamp.
Construct the preamp as shown and connect it to the audio amp, if it
hums when you touch it you did good.
If the amp does not work it is most likely that your bias is off (or the polarity of one of your
capacitors is backwards) , put a
oscilloscope / or multimeter on the "to audio amp pin".
Remove the 1.5m resistor and check where the bias is on the
oscilloscope / or multimeter and add a replacement value for the 1.5m
ohm that creates exactly 1/2 that voltage on the audio amp side.