Multimedia 2.1 channel speaker system speaker protector

The number of multimedia computer owners is increasing day by day, and they are all equipped with 2.1-channel speaker systems, that is, two small speakers plus a subwoofer (the subwoofer has a transformer and a three-channel amplifier, volume and tone control, etc.), while most low-end and mid-range 2.1-channel speaker systems do not have speaker protection circuits, because manufacturers design the appearance to be particularly beautiful to attract customers in order to save costs. I believe that readers who own these speakers will have the following phenomenon: every time the speakers are powered on and off, the three speakers will have a current impact sound. The impact current is actually caused by the instantaneous DC output of power on and off, and the consequences are: the life of the speaker voice coil is shortened if it is small, and the speaker voice coil is burned immediately if it is large. Without a speaker protection circuit, if the amplifier fails to output DC voltage, the DC voltage will destroy the speaker voice coil in just a few seconds! Therefore, in order to be more assured, we should add a three-channel speaker protector to the speaker for your beloved 2.1-channel speaker system! Let the protector always protect your speakers.

The schematic diagram is as follows:

When the power is turned on, since the base of T2 is at a low level, T1 is not turned on, the relay will not be attracted, and the base voltage of T2 charges C2 along with R1. After about 5 seconds, the base of T2 becomes a high level, T2 is turned on, and the base of T1 also becomes a high level, making T1 turned on. At this time, the relay is attracted, thereby realizing a startup delay of about 5 seconds before connecting the power amplifier to the speaker, avoiding the DC output of the power amplifier to impact the speaker at the moment of startup, thereby protecting the speaker.

When shutting down, since C1 is only 47uF, it will run out of power quickly, and the relay will immediately cut off the connection between the power amplifier and the speaker. However, the power amplifier does not consume power so quickly, so the DC power failure of the power amplifier does not impact the speaker, thus protecting the speaker.

When any of the three amplifiers fails to 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 of T2 is at a low level, making T1 non-conducting. The relay immediately cuts off the path between the amplifier and the speaker, thus avoiding damage to the speaker by DC. When it is a negative voltage, T3 is turned on, C2 is discharged, and the base of T2 is at a low level, making T1 non-conducting. The relay immediately cuts off the path between the amplifier and the speaker, thus avoiding damage to the speaker by DC.

Component selection and use: T1, T2, T3, T4 use NPN transistor C945, C1's withstand voltage should be 35V or above, resistors use 1/4W five-color ring metal film resistors, relays use four-unit (one group for each left and right, two groups for subwoofers in parallel to increase the current conduction), the circuit board design should be beautiful, silver-plated and printed with blue oil, small in area, and easy to install (if you want to see the author's actual physical picture, please go online: http://www.v9688.com), and the AC power supply of the protection board can be directly used with the original power amplifier. Note: Point G must be connected to the ground (0V) of the original power amplifier, otherwise it will not work for DC detection. Points A, B, C, D, E, and F are only connected to the positive poles of the power amplifier and the speaker, and the negative poles are connected.

You can buy a three-channel speaker protector for your beloved 2.1-channel speaker system for only 20 or 30 yuan! Let the protector always protect your speakers and let you use your multimedia computer with confidence!