Below is my constructed audio amp and graphs that corresponds to the voltage at the collector of Q1 and the emitter of Q2. Everything works great until I add the capacitor to protect the speaker (8Ω). Then for some reason the emitter voltage becomes cut off. This is my first design so I am a newbie. I expected the capacitor to just act like an open circuit at the high frequency..?
Then for some reason the emitter voltage becomes cut off.
When the signal at the collector of Q1 is high, Q2 (an emitter follower) is a good source of current into the 8 ohm load (via the 330 uF capacitor, C2) but, when the signal at Q1's collector goes low, because the load (8 ohms) is such a low value AND C2 is charged-up, all you have in the circuit is the 500 ohm resistor (R3) trying to discharge the 330 uF capacitor and it just isn't man enough for the job. This is one reason why we use push-pull stages to drive loudspeakers.
You could try lowering R3 in value and see the situation somewhat improve but then you'll find that the circuit's quiescent current rises quite high.