I designed an audio amplifier that can be made from general-purpose transistors (not needing VHF transistors that might cost more money) that are used for audio applications. You can make audio amplifiers with power amplifier ICs (integrated circuits) or operational amplifiers. However, most of those IC (integrated circuits) need voltages of at least 4.5 V. 

You can make basic transistor amplifiers with:

1. Fixed bias.

2. Stabilised bias.

3. Feedback bias.

I tried the first and third biasing methods.

I made this circuit with BC559 BJT (Bipolar Junction) PNP transistors.

The only difference between BJT NPN and BJT PNP transistors is the direction of current conduction.

You can use the following NPN transistors:

- BC337, 2N2222, PN100

PNP transistors:

- BC327, 2N2907A

I included a small orange ceramic capacitor (about 10 nF) for the second transistor amplifier to filter high-frequency noise.

Step 1: Design the Circuit

I have drawn the circuits in PSpice simulation software student edition version 9.1:

My circuit is useful for microphone and Line In amplification, will cost less money, and will last longer because I increased the resistor values to reduce the power dissipation.

Step 2: Simulations

I used the old PSpice software to simulate the circuit.

Frequency domain simulations:

Step 3: Build the Circuit

This photo is showing my transistor amplifier made with BJT NPN transistors:

I increased the Rc values to 10 kohms. I used a USB oscilloscope to test my circuit. Increasing the Rc values has increased the circuit gain but reduced the bandwidth to just 1 kHz due to transistor stray capacitance. I included a small orange ceramic capacitor (about 10 nF) for the second transistor amplifier to filter high-frequency noise.

Conclusion

Also, keep in mind that BC547, BC548, BC549, BC557, BC558, and BC559 are listed in the bad components project due to very low maximum power and maximum current ratings. Thus I suggest that you use other types of transistors.