18 W AUDIO AMPLIFIER

10W Audio Amplifier with Bass-Boost with NE5532 and TIP41

Description:

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).

Parts List

P1	22K Log.Potentiometer (Dual-gang for stereo)
P2	100K Log.Potentiometer (Dual-gang for stereo)
R1	820R 1/4W Resistor
R2,R4,R8	4K7 1/4W Resistors
R3	500R 1/2W Trimmer Cermet
R5	82K 1/4W Resistor
R6,R7	47K 1/4W Resistors
R9	10R 1/2W Resistor
R10	R22 4W Resistor (wirewound)
C1,C8	470nF 63V Polyester Capacitor
C2,C5	100µF 25V Electrolytic Capacitors
C3,C4	470µF 25V Electrolytic Capacitors
C6	47pF 63V Ceramic or Polystyrene Capacitor
C7	10nF 63V Polyester Capacitor
C9	100nF 63V Polyester Capacitor
D1	1N4148 75V 150mA Diode
IC1	NE5532 Low noise Dual Op-amp
Q1	BC547B 45V 100mA NPN Transistor
Q2	BC557B 45V 100mA PNP Transistor
Q3	TIP42A 60V 6A PNP Transistor
Q4	TIP41A 60V 6A NPN Transistor
J1	RCA audio input socket

Power supply parts:

R11	1K5 1/4W Resistor
C10,C11	4700µF 25V Electrolytic Capacitors
D2	100V 4A Diode bridge
D3	5mm. Red LED
T1	220V Primary, 12 + 12V Secondary 24-30VA Mains transformer
PL1	Male Mains plug
SW1	SPST Mains switch