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Bass Boosting Audio Amplifier

2015-01-06 00:25  
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Figure 1 

Parts List

The design of the circuit aims to create an audio amplifier that would provide more attention to the boosting of bass frequency while giving a power of 10 Watts into 8 Ohms load.

NE5532 – an internally compensated low noise dual operational amplifier with features such as full power bandwidth up to 140 KHz, input noise voltage of 8 nV, common mode rejection ratio, 9 V/us slew rate, high DC voltage gain, 32 V peak to peak voltage swing, wide supply voltage range from 3 V to 12 V, unity gain bandwidth at 10 MHz, and internal frequency compensationBC557 –PNPgeneral purpose transistors used for amplification and switching due to its low current and low voltageTIP42 – a siliconPNPpower transistor with TO-220C package used for general purpose and medium power linear switching applications

The circuit is utilizing the functionality of dual op-amp IC with the limitation in the power output which should fall in the range of 9.5 W to 11 W because the supply rails will not be able to handle voltages exceeding 18 V. This type of amplifier circuit is commonly used as driver for small loudspeaker cabinets where the frequency range of the bass is somewhat given up. For this reason, the feedback loop of the amplifier has been added with bass boost control in order to reduce the loss of audio quality and prevail over the existing problem.

The peak curve of the bass can reach a maximum gain of positive 16.4 dB at 50 Hz frequency. The frequency response of the amplifier will show a mild curve of rising even when the bass control is rotated fully counterclockwise in any case. The curve and frequency proportionality shows that the gain is 0.8 dB at 400 Hz, 4.7 dB at 100 Hz, and 6 dB at 50 Hz frequency.

The connection of C3, C4, IC1, and the power supply are common to both channels although only the left channel is shown. The linear adjustment of bass boost is ensured by a logarithmic type of potentiometer as denoted by P2. Q1 must be in thermal contact with D1 while the transistors Q3 & Q4 should be mounted on heatsink. The resistor R3 is set to minimum resistance as well as the volume being set to the minimum.

The current being drawn is adjusted to approximately 20 mA to 25 mA by R3 after the circuit is powered ON. If necessary, the current will be re-adjusted if the current is varying for about 15 minutes. To eliminate the ground loops and hum, a proper grounding is very essential. This is made possible by connecting C9 to the output ground and C2, C3, C4, J1, & P1 to the same ground sides point while the input and output grounds are separately connected to the power supply grounds.

The audio amplifier with bass boost can be connected directly to tape recorders, CD players, and tuners, to satisfy the listeners taste for boost level. The bass boost can compensate for bass level in modern recordings which is limited in order to maximize loudness. For guitarists and bassists, the bass booster can provide help to unearth a sound that is positively subterranean.


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