It is best to keep Rin as high as possible as this sets the input impedance, and in most applications, the higher the better, preferably above 10K and Rf < 10M
But for maximum gain, you will get away with Rin=4.7K and Rf=4.7M.
The supply voltage generally ranges from about 9v to 28v
Shown right is a graph comparing input and output signals. The gain is set at -10 for better illustration
If the signal sounds distorted, it is likely that the wave is clipping. This is when the top and bottom of the sound wave are lost, clipped. This is because the amplifier cannot produce large enough output voltages due to the supply voltage being too low.
If viewed on an oscilloscope it might look something like the lower graph.
There are a few ways to get around a clipping output. Try one or more of the following:
- Increase the power supply voltage - but do not go above 28 volts.
- Reduce the input signal using a volume control (preset or potentiometer).