Speaker protector for multimedia 2.1-channel speaker system

The owners of multimedia computers are increasing, and they are all equipped with a 2.1-channel speaker system, that is, two small speakers plus a subwoofer (subwoofer with transformer and three-channel power amplifier, volume and tone control, etc.), and most of them The low-end 2.1-channel speaker system does not have a speaker protection circuit, because the manufacturer has designed the appearance to be particularly beautiful to attract customers in order to save costs. I believe that readers with these speakers will have the following phenomenon: each time when the speaker is powered on and off, there will be current impact sound from the three speakers. The inrush current is actually caused by the instantaneous DC output when power is turned on and off. The consequences are: the life of the speaker voice coil is shortened when it is small, and the speaker voice coil is burned immediately when it is large. When there is no speaker protection circuit, if the power amplifier has a fault and outputs DC voltage, the DC voltage can destroy the speaker voice coil in just a few seconds! Therefore, in order to rest assured, let's add a three-channel speaker protector to the beloved 2.1 channel speaker system! Let the protector take care of your speakers at all times.

The schematic diagram is as follows:

When the base of T2 is at low level, T1 is not turned on when the power is turned on, and the relay will not pull in. The base voltage of T2 charges C2 with R1, and the base of T2 turns to high level after about 5 seconds. T2 is turned on so that the base of T1 also becomes high and T1 is turned on. At this time, the relay pulls in, so that the power-on delay is about 5 seconds before the power amplifier is connected to the speaker, avoiding the power amplifier output at the moment of power-on The direct current impacts the horn to protect the horn.

During shutdown, the C1 was only 47uF, and it quickly ran out of power. The relay immediately cut off the channel between the power amplifier and the speaker, and the power amplifier did not consume the power so quickly. Therefore, the DC power failure of the power amplifier did not impact the speaker, which provided protection Speaker function.

When any one of the three power amplifiers has a faulty output DC voltage, it is transmitted to T3 and T4 by R2-R4 for detection. When it is a positive voltage, T4 is turned on, C2 is discharged, and the base level of T2 is extremely low so that T1 is not turned on. The relay immediately cut off the path between the power amplifier and the speaker, thereby avoiding the damage of the DC to the horn. When the negative voltage is applied, T3 is turned on, C2 is discharged, and the T2 base is extremely low so that T1 is not turned on. The relay immediately cuts off the power amplifier The channel with the speaker, thus avoiding the damage of the DC to the speaker.

Component selection and use: NPN triode C945 for T1, T2, T3, T4, C1 withstand voltage of 35V or above, 1 / 4W five-color ring metal film resistor for resistance, quadruple for relay (one set for each left and right, The subwoofer is used in parallel with two sets to increase the current conduction), the circuit board design should be beautiful, the silver-plated blue oil should be upgraded, the area should be small, and it should be installed easily (if you want to see the actual physical picture of the author, please go online See: http: //), install the AC power supply using the protection board directly to use the original power amplifier. Note: Point G should be connected to the ground (0V) of the original power amplifier, otherwise DC detection will not work. Points A, B, C, D, E, and F are only connected to the positive poles of the amplifier and speakers, and the negative poles are allowed to communicate with each other.

You can give your beloved 2.1-channel speaker system a three-channel speaker protector for two or thirty yuan! Let the protector take care of your speakers at all times. Let you use the multimedia computer with confidence!

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