I have attached a schematic of my audio amplifier circuit. The circuit is meant to run off of a 5V supply, and drive a 4ohm speaker. I want at least a gain of 15, with as little distortion as possible.

The circuit works fine in simulation. When I built the circuit it operated properly when not under load, but when I attached the speaker the signal was severely distorted. The entire top half of the signal was clipped.

I would appreciate advice on how to correct this from people who have some experience with this sort of circuit.

Any help is appreciated.

 

The string with R4 looks wrong. I see 4 ma going through a 1 k resistor, 2 transistors, and 2 diodes with a 5 volt supply. Not enough voltage to run that string of parts.

Anybody else is free to point out if I'm wrong.

 

The string with R4 looks wrong. I see 4 ma going through a 1 k resistor, 2 transistors, and 2 diodes with a 5 volt supply. Not enough voltage to run that string of parts.

Anybody else is free to point out if I'm wrong.

That's what I see. The output transistors should be smoking. I'm guessing that Q8 is already dead, which would explain why the top half of the signal is clipped.
The unballasted output transistors are prime candidates to burn out while that issue is being corrected.