Currently, ICs has been used in many audio amplifiers,especially small circuit. It is convenient to use transistors.But when you need to use transistors, it has several advantages, such as saving you can take old equipment come to made small circuits easier than the IC. Which may be difficult to find. Take a look at these circuits. Maybe you get the idea of it.
Power Amplifier OTL by AC176+AC126
Mr Somsak is my friend who like to make power amplifier so much. but he do not well electronic man. I so introduce he need make easy project before. This circuit is simple power amplifier OTL that mini watt output but is older circuit.
They uses transistors example number are AC176 , AC126 and BC109. which there has other a few components. They are used power Supply Voltage 9Volt only. I hope it will be once circuit so you like and well ideas.
Power Amplifier OTL Cassette Radio Booster by TIP41+TIP42
This is mini Power Amplifier OTL for Cassette Radio Booster. it have transistor TIP41 + circuits of TIP42 Drive speaker sound. Volt supply see in image.
Simple Amplifier by Transistor AC128
I find this in my old circuit electronics book. It is very a small power amplifier, but good quality audio class AB amplifier in hi-fi applications. The component capable of delivering 2W continuously an used the AC128 thansistor into a 8 ohm load and 5W peak. with the proper 9 volt unregulated power supply.
The circuit of VMOS 10 Watt Amplifier
Hello! This the circuit amplifies small-sized.it uses the equipment VMOS , number BD512 and BD522. which be pillar heart of the circuit. By it very the circuit is the character of OTL , make build easy and the price economizes. It is giving watt about 10W when , use force against 8ohm size loudspeakers and use a place turn on the power 33V sizes that the trend about 1.5A yes.