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2 Watt Mini Audio Amplifier circuit diagram

2015-01-06 01:14  
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This circuit is inexpensive, easy and quite simple. This is general audio amplifier which can be used for computer, CD player or other devices which have headphone output.

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.

Schematic Diagram:

2 Watt Mini Audio Amplifier circuit

Components list:

P1 = 10KLog.Potentiometer
R1,R2 = 33K1/4W Resistors
R3 = 33R1/4W Resistor
R4 = 15K1/4W Resistor
R5,R6 = 1K1/4W Resistors
R7 = 680R1/4W Resistor
R8 = 120R1/2W Resistor
R9 = 100R1/2W Trimmer Cermet
C1,C2 = 10?F63V Electrolytic Capacitors
C3 = 100?F25V Electrolytic Capacitor
C4,C7 = 470?F25V Electrolytic Capacitors
C5 = 47pF63V Ceramic Capacitor
C6 = 220nF63V Polyester Capacitor
C8 = 1000?F25V Electrolytic Capacitor
D1 = 1N414875V 150mA Diode
Q1 = BC560C45V 100mA PNP Low noise High gain Transistor
Q2 = BC33745V 800mA NPN Transistor
Q3 =TIP31A60V 4A??? NPN Transistor
Q4 = TIP32A60V 4A??? PNP Transistor
SW1SPST switch
SPKR3-5 Watt Loudspeaker, 8, 4 or 2 Ohm impedance

Technical data:

Output power:1.5 Watt RMS @ 8 Ohm, 2.5 Watt @ 4 Ohm, 3.5 Watt @ 2 Ohm (1KHz sinewave)Sensitivity:100mV input for 1.5W output @ 8 OhmFrequency response:30Hz to 20KHz -1dBTotal harmonic distortion@ 1KHz & 10KHz: Below 0.2% @ 8 Ohm 1W, below 0.3% @ 4 Ohm 2W, below 0.5% @ 2 Ohm 2W.

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