Full-featured subwoofer power amplifier 02

Shown are the post-stage power amplifier circuit and the pre-stage signal processing circuit of the subwoofer power amplifier. Here, two LM3886
high-power ICs recently produced by NS Company in the United States are specially selected to be connected in BTL mode to drive the speaker with a standard impedance of 8fl. Under the requirement of distortion less than 0.2%, it can continuously output 100W sine wave rated power. It needs to be explained clearly that I-M3886 is an IC improved by NS Company based on I-M3886. Although its product introduction states that each IJM3886 can output a maximum 68W sine wave rated power, its internal design has a complete over-power consumption protection function. , when used under power supply conditions exceeding 50w output power , it will protect and cause distortion of the output signal. We should only let it work when the rated output power is not greater than In the state of 50w. As we all know, slightly better high-power amplifiers are equipped with speaker protection circuits, and the switch that cuts off the operating current of the speaker can only be a relay contact without any voltage drop. However, when the relay is installed in an active speaker, when the speaker emits a strong low- frequency sound, the contacts of the relay will vibrate mechanically and cause sound interruption. Therefore, it is not suitable for active speakers with larger power subwoofers. Using a horn protection relay on the circuit may affect the normal operation of the system. In this way, the power amplifier is required to have a very complete and reliable safety protection function. This is also the fatal flaw of using discrete components to make such sound quality. We have reviewed the three subwoofer active speakers produced by YAMAHA and SONY. After conducting actual measurements, we found that their output power is actually limited to about 50w, and they rarely work in situations with heavy bass. Using the LM3886 power amplifier IC as a subwoofer active power amplifier can take advantage of its complete protection functions such as overheating, overcurrent, overvoltage, and overpower consumption to avoid the need for other speaker protection circuits that need to be designed separately. 6 Actual use proof, two The LM3886 power amplifier IC should be equipped with an aluminum radiator with a size of ZOOmm×50mm×30mm, and flowing air should be maintained on the radiator . For this reason, the pre-stage circuit and the post-stage power amplifier are specially designed to be separated into two printed circuit boards, so that after the power amplifier board is installed separately on the radiator, it can be installed inside the box inside the inverter tube. After the 100W sine wave rated output power is enough to drive the 12Ⅳ caliber woofer to work , we must avoid adding too much output power to the speaker. For this reason, in the pre-circuit, two resistors composed of R123 and VD117.VD118 are specially designed.