The home audio amplifiers such as subwoofer amplifier in our home audio system is usually powerful. The output of these amplifiers usually connected to a large power loudspeaker such as subwoofer. When we activates the power to the amplifier, the loudspeaker works with annoying "TTAP" sound and this will damage your loudspeaker. So this circuit keep the situation clear when you power up your home theater. It allows the sound to fade in to the speaker by activating a relay.
Circuit Diagram of Subwoofer Protection : Click to enlarge
Working
The loudspeaker protection system circuit is shown in the figure. The loudspeaker wont turn on when the amplifier is switched ON. TL071 IC and transistor will create a time delay to start the relay switch, by the time voltages in the amplifier will reach in a stabilized state. Then the relay get activated and the subwoofer will produce sound. This circuit will help you to avoid dissonance and can also be used time delay purposes.
Notes
- Time delay can be varied by adjusting values of capacitors C1, C2 and zenar voltage.
- The led's can be used to identify the ON/OFF state of the speaker.
Parts List
- R1 = 22K
- R2-3 = 390K
- R4 = 470K
- R5 = 1M
- R6-7-8-9-10-10 = 10K
- R11 = 820 OHM
- C1-2-3 = 47uF 63V
- C4-5 = 100uF 25V
- Q1 = BC560C
- Q2-3-4 = BC550C
- Q5 = BD139
- D1-2-3 = 1N4148
- D4 = GREEN 5mm LED
- D5 = Red 5mm LED
- IC1 = TL071
- RL1,RL2 = Relay 12V Dc Omron G2R2
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