This project  is based almost directly on the typical application circuit in the National Semiconductor specification sheet. You can also use the TDA2050 , which has almost identical performance and the same pinoutssource

This is Modular Audio Preamplifier,high quality, discrete components design with Input and Tone Control Modules.The circuit consists of two module:Main module and tone control module.Features:

Main Module Input sensitivity:
250mV RMS for 1V RMS output
Tone Control Module Input sensitivity:
1V RMS for 1V RMS output
Maximum output voltage:
13.4V RMS into 100K load, 11.3V RMS into 22K load, 8.8V RMS into 10K load
Frequency response:
flat from 20Hz to 20KHz
Total harmonic distortion @ 1KHz:
1V RMS 0.002% 5V RMS 0.003% 7V RMS 0.003%
Total harmonic distortion @10KHz:
1V RMS 0.003% 5V RMS 0.008% 7V RMS 0.01%

source

This is 3- 5 Watt Class-A Audio Amplifier circuit.Behaves like a one-valve operated amplifier,simple circuitry,no cross-over distortion.The circuit was usually implemented by means of a multiple type valve, e.g. a triode pentode ECL86.Common features for those amplifiers were: Class A operation, output power in the 3 – 5W range, input sensitivity of about 600mV for full output power, THD of about 3% @ 3W and 1KHz.source

Mini-box is 2W Amplifier circuit.It is designed for self-powered 8, 4 & 2 Ohm loudspeakers with Bass-boost switch.This amplifier was designed to be self-contained in a small loudspeaker box. It can be feed by Walkman, Mini-Disc, iPod and CD players, computers and similar devices fitted with line or headphone output. The circuit was deliberately designed using no ICs and in a rather old-fashioned manner in order to obtain good harmonic distortion behavior and to avoid hard to find components.source

This is 10W Audio Amplifier circuit with Bass-boost,High Quality, very simple design,No preamplifier required.This design is based on the 18 Watt Audio Amplifier, and was developed mainly to satisfy the requests of correspondents unable to locate the TLE2141C chip. It uses the widespread NE5532 Dual IC but, obviously, its power output will be comprised in the 9.5 – 11.5W range, as the supply rails cannot exceed ±18V.source