Audio008

                                          

10 Watt Audio Amplifier with Bass-Boost
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Schematic design of 10W audio amplifier + Power Supply
Part Components of 10W Audio Amplifier:
Capacitors	Resistors
C1,C8 = 470 nF / 63V Polyester C2,C5 = 100 μF / 25V Electrolytic C3,C4 = 470 μF / 25V Electrolytic C6      =   47 pF / 63V Ceramic or Polystyrene C7      =   10 nF / 63V Polyester C9      = 100 nF / 63V Polyester Semiconductors IC1     = NE5532 Q1      = BC547B Q2      = BC557B Q3      = TIP42A Q4      = TIP41A D1      = 1N4148	R1          =   820Ω ¼W R2,R4,R8=   4K7Ω ¼W R3          =   500Ω ½W Trimmer Cermet R5          =   82KΩ ¼W R6,R7     =   47KΩ ¼W R9          =     10Ω ½W R10        =  0.22Ω 4W wirewound P1      =   22KΩ Log.Potentiometer              (Dual-gang for stereo) P2      = 100KΩ Log.Potentiometer              (Dual-gang for stereo) Others J1       = RCA audio input socket
Part Components of Power Supply :
Capacitors	Resistors
C10,C11 =  4700 μF / 25V Electrolytic Others T1 220V Primary, 12 + 12V Secondary 24-30VA Mains transformer PL1 Male Mains plug SW1 SPST Mains switch	R11    = 1K5Ω ¼W Diodes D2 100V 4A Diode bridge D3 LED (5mm. Red)
Notes
High Quality, very simple design and no need for a preamplifier. 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. As amplifiers of this kind are frequently used to drive small loudspeaker cabinets, the bass frequency range is rather sacrificed. Therefore a bass-boost control was inserted in the feedback loop of the amplifier, in order to overcome this problem without quality losses. The bass lift curve can reach a maximum of +16.4dB @ 50Hz. In any case, even when the bass control is rotated fully counterclockwise, the amplifier frequency response shows a gentle raising curve: +0.8dB @ 400Hz, +4.7dB @ 100Hz and +6dB @ 50Hz (referred to 1KHz).   Can be directly connected to CD players, tuners and tape recorders. Schematic shows left channel only, but C3, C4, IC1 and the power supply are common to both channels. Numbers in parentheses show IC1 right channel pin connections. A log type for P2 ensures a more linear regulation of bass-boost. Don't exceed 18 + 18V supply. Q3 and Q4 must be mounted on heatsink. D1 must be in thermal contact with Q1. Quiescent current (best measured with an Avo-meter in series with Q3 Emitter) is not critical. Set the volume control to the minimum and R3 to its minimum resistance. Power-on the circuit and adjust R3 to read a current drawing of about 20 to 25mA. Wait about 15 minutes, watch if the current is varying and readjust if necessary. 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 C9 at the output ground. Then connect separately the input and output grounds at the power supply ground.
Technical Data
Output power: 10 Watt RMS @ 8Ω (1KHz sinewave) Sensitivity: 115 to 180mV input for 10W output (depending on P2 control position) Frequency response: 30Hz to 20KHz -1dB Total harmonic distortion @ 1KHz : 0.1W 0.009% 1W 0.004% 10W 0.005% Total harmonic distortion @100Hz:  0.1W 0.009% 1W 0.007% 10W 0.012% Total harmonic distortion @10KHz:   0.1W 0.056% 1W 0.01% 10W 0.018% Total harmonic distortion @ 100Hz and full boost: 1W 0.015% 10W 0.03% Max. bass-boost referred to 1KHz: 400Hz = +5dB; 200Hz = +7.3dB; 100Hz = +12dB; 50Hz = +16.4dB; 30Hz = +13.3dB Unconditionally stable on capacitive loads

Source : Electronics Lab