Various kinds of stereo amplifier are readily available in market. But if we ask for good quality stereo amplifier with graphic equaliser facility, it’s price become very high. The cheaper varieties are generally based on discrete transistors, and suffer from drawback such as uncontrolled hum, ineffective tone control, poor base response, thermal runway etc. the use of inter-stage transformers in such circuits reduces their versatility.
Here you find the tutorial to build 8W + 8W Stereo Amplifier with Graphic Equalisers.
8W+8W stereo amplifier is a reliable and perfect enough to implemented it in a real working environment. This project is very helpful because it is capable of providing an output of 8 watts into each channel. By using this circuit we can control and blend frequencies and tone over wide range in order to produce perfect sound because it contains in-build 6-band graphic equaliser.
- Can be used as an AF output stage of recorder player, CD player or just as an independent stereo amplifier itself.
- Offers high degree of flexibility as it can operate in environment temperature between 00 to 700
- Can operate off voltage in the 5V-20V range.
- Internally protected against input and output circuiting.
- Protected from high voltage (up to 40V).
- Noise and distortion level is extremely low and no turn-on transients occur.
- Low cost (around $3)
Working of the circuit
The circuit of the complete 8W+8W stereo amplifier is shown in figure 1. The heart of the circuit 8W+8W stereo amplifier is dual band graphic equaliser IC LM1458 (IC1). Corresponding pot is used to determine the gain of op-amp. The audio frequency spectrum is covered by six different band of tone control. For volume control we use VR13 and VR14, where VR13 control volume of left channel and VR14 control volume of right channel. In table I we show frequency control by different pot.
The out of IC1 is given to the input of two low cost op-amps IC (IC2 and IC3) for necessary power amplification. These two IC are current and thermal protected. The output from pin 1 and 7 of IC1 is given to inverting pin 1 of IC2 and IC3 through coupling capacitor C19 and C23 respectively as shown in figure 1. The output from pin 4 of both IC (IC2 and IC3) is given to the loudspeaker through capacitor C21 and C24 respectively.
For noise reduction we serially connect a resistor R25 and a capacitor C25 from output pin 4 to the ground as shown in figure 1. The LED dancing arrays, the circuit of which is given in figure 2, may be added to the main circuit. The LEDs flicker with a brightness level which is dependent upon the output power.
|Control Frequency||Control Potentiometer|
|Left Channel||Right Channel|
PARTS LIST OF 8W+8W STEREO AMPLIFIER CIRCUIT
|Resistor (all ¼-watt, ± 5% Carbon)|
|R1, R8, R19, R20 = 4.7 KΩ|
R2 – R7, R13 – R18 = 33 KΩ
R9, R12 = 100 KΩ
R10, R11 = 330 KΩ
R21, R22 = 470 KΩ
R23, R26 = 2.2 Ω
R24, R27 = 220 Ω
R25, R28 = 1 Ω
R29, R30 = 1 KΩ
VR1 – VR14 = 100 KΩ potentiometer
|C1, C14 = 50 µF, 25V (Electrolytic Capacitor)|
C2, C8 = 47 nF (Ceramic Disc)
C3, C9 = 15 nF (Ceramic Disc)
C4, C10 = 8.2 nF (Ceramic Disc)
C5, C11 = 4.7 nF (Ceramic Disc)
C6, C12 = 1.5 nF (Ceramic Disc)
C7, C13 = 300 pF (Ceramic Disc)
C15 – C19, C23 = 10 µF, 25V (Electrolytic Capacitor)
C20, C22 = 470 µF, 25V (Electrolytic Capacitor)
C21, C24 = 2200 µF, 25V (Electrolytic Capacitor)
C25 – C27 = 0.1 µF (Ceramic Disc)
|IC1 = LM1458|
IC2, IC2 = LM2002A
T1 = BC557
T2 = BC547
D1, D2 = 1N34
LED1 – LED12 = 500mm LED
|LS1, LS2 = 4Ω, 10W speakers|