18W Audio Amplifier
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-- High Quality very simple unit |
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-- No need for a preamplifier |
Circuit diagram:
Amplifier parts:
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P1 = 22K |
Log.Potentiometer (Dual-gang for stereo) |
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R1 = 1K |
1/4W Resistor |
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R2 = 4K7 |
1/4W Resistor |
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R3 = 100R |
1/4W Resistor |
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R4 = 4K7 |
1/4W Resistor |
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R5 = 82K |
1/4W Resistor |
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R6 = 10R |
1/2W Resistor |
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R7 = R22 |
4W Resistor (wirewound) |
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R8 = 1K |
1/2W Trimmer Cermet (optional) |
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C1 = 470nF |
63V Polyester Capacitor |
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C2,C5 = 100µF |
3V Tantalum bead Capacitors |
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C3,C4 = 470µF |
25V Electrolytic Capacitors |
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C6 = 100nF |
63V Polyester Capacitor |
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D1 = 1N4148 |
75V 150mA Diode |
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IC1 = TLE2141C |
Low noise,high voltage,high slew-rate Op-amp |
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Q1 = BC182 |
50V 100mA NPN Transistor |
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Q2 = BC212 |
50V 100mA PNP Transistor |
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Q3 = TIP42A |
60V 6A PNP Transistor |
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Q4 = TIP41A |
60V 6A NPN Transistor |
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J1 |
RCA audio input socket |
Power supply parts:
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R9 = 2K2 |
1/4W Resistor |
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C7,C8 = 4700µF |
25V Electrolytic Capacitors |
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D2 |
100V 4A Diode bridge |
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D3 |
5mm. Red LED |
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T1 |
220V Primary, 15 + 15V Secondary 50VA Mains transformer |
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PL1 |
Male Mains plug |
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SW1 |
SPST Mains switch |
Notes:
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Can be directly connected to CD players, tuners and tape recorders.
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Don't exceed 23 + 23V supply.
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Q3 and Q4 must be mounted on heatsink.
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D1 must be in thermal contact with Q1.
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Quiescent current (best measured with an Avo-meter in series with Q3 Emitter) is not critical.
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Adjust R3 to read a current between 20 to 30 mA with no input signal.
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To facilitate current setting add R8 (optional).
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A correct grounding is very important to eliminate hum and ground loops. Connect in the same point the ground sides of J1, P1, C2, C3 &C4. Connect C6 at the output ground.
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Then connect separately the input and output grounds at the power supply ground.
Technical data:
Output power: 18 Watt RMS @ 8 Ohm (1KHz sinewave)
Sensitivity: 150mV input for 18W output
Frequency response: 30Hz to 20KHz -1dB
Total harmonic distortion @ 1KHz: 0.1W 0.02% 1W 0.01%
5W 0.01% 10W 0.03%
Total harmonic distortion @10KHz: 0.1W 0.04% 1W 0.05%
5W 0.06% 10W 0.15%
Unconditionally stable on capacitive loads
Title: 18W Audio Amplifier
electronic circuit
Source: www.redcircuits.com
Published on: 2005-02-01
Reads: 1924
Print version: 
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