Audio002

                                          

2 Watt Mini Audio Amplifier
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Schematic design of 2W mini audio amplifier
Part Components of Mini Audio Amplifier:
Capacitors	Resistors
C1,C2 =     10μF / 63V Electrolytic C3      =   100μF / 25V Electrolytic C4,C7 =   470μF / 25V Electrolytic C5      =     47pF / 63V Ceramic C6      =   220nF / 63V Polyester C8      = 1000μF / 25V Electrolytic Transistors Q1 = BC560C Q2 = BC337 Q3 = TIP31A Q4 = TIP32A	P1      = 10KΩ Log.Potentiometer R1,R2 = 33KΩ ¼W R3      =   33Ω ¼W R4      = 15KΩ ¼W R5,R6 =   1KΩ ¼W R7      =  680Ω ¼W R8      =  120Ω ½W R9      =  100Ω ½W Trimmer Cermet Others SW1 SPST switch SPKR 3-5 W Loudspeaker; 8, 4 or 2Ω impedance D1 = 1N4148
Notes:
This amplifier was designed to be self-contained in a small loudspeaker box. It can be feed by Walkman, Mini-Disc and CD players, computers and similar devices having line or headphone output. Of course, in most cases you'll have to make two boxes to obtain stereo. The circuit was deliberately designed using no ICs and in a rather old-fashioned manner in order to obtain good harmonic distortion behaviour and to avoid hard to find components. The amplifier(s) can be conveniently supplied by a 12V wall plug-in transformer. Closing SW1 a bass-boost is provided but, at the same time, volume control must be increased to compensate for power loss at higher frequencies. In use, R9 should be carefully adjusted to provide minimal audible signal cross-over distortion consistent with minimal measured quiescent current consumption; a good compromise is to set the quiescent current at about 10-15 mA. To measure this current, wire a DC current meter temporarily in series with the collector of Q3.
Technical Data
Output power: 1.5 Watt RMS @ 8Ω, 2.5 Watt @ 4Ω, 3.5 Watt @ 2Ω (1KHz sinewave) Sensitivity: 100mV input for 1.5W output @ 8Ω Frequency response: 30Hz to 20KHz -1dB Total harmonic distortion @ 1KHz & 10KHz: Below 0.2% @ 8Ω 1W, below 0.3% @ 4Ω 2W, below 0.5% @ 2Ω 2W.

Source : Electronics Lab