Electrical – Speaker BJT Amplifier – very low gain

amplifier

First of all this is not related to a HW or anything; I just wanted to build an audio amplifier and test my skills.
I really don't see why my design is not working as intended, without the speaker load it amplifies the input signal just right but when I connect the speaker load (4 Ohm) the power of the speaker is limited to microwatts. Can anyone help?
Sorry I didn't sketch the circuit in the editor since I already had drawn it in LTspiceamp circuit
P.S. I actually have built the circuit but I can barely hear something coming from the speaker when I blow on the mic.

Best Answer

The gain of the last stage is approximately equal to: $$Gain_3 = {{R8}\over{R4}} = {{4}\over{2200}}=0.001818$$ You must use a push-pull emitter follower. Transistors desirable to take a large gain. With such a supply voltage using two stage voltage gain enough (\$Gain=1000 \div 5000\$) output and push-pull emitter follower (gain approximately equal 1). The last stage can be done on a single-ended power transistor with the radiator cooling. But modal current in this case is very high.