Complete set of car radio equipment audio power amplifier 02

This article introduces an optimal and interesting high-quality amplifier structure for audio playback in automobiles
, which can be realized at the lowest cost. And this solution can also be used in small portable music centers. The characteristic of this power amplifier is that there is no
additional amplifier for the low channel. The speaker of the low-frequency channel is connected to the output terminals of the two stereo channels through a filter. One of the signals
is inverted, thus forming a bridge connection circuit. When powered by a low voltage In this case,
sufficient power can be obtained from the compressed low-frequency public speakers. The 6
    audio power amplifier circuit is shown in Figure 5-115. The dual operational amplifier ici constitutes a preamplifier, and half of it works in the anti-phase state in the left
channel , while The other half works in the same phase on the right channel, and the amplification factor of the preamplifier is equal to 1. In addition to
inverting the signal in one of the channels, it also provides the bias voltage q at the input end of the power amplifier IC2 and IC3 integrated circuits in order to make
the DC voltage at the output end of the power amplifier increase steadily and slowly after the power supply voltage is turned on, eliminating the need to turn on the power supply. For the instantaneous "click
" sound, a "click" noise canceling circuit R6 CS is introduced in the circuit. When the power is turned on, the voltage on CS increases slowly,
which will not cause the output to produce a "click" sound. Diode VD2 is used to quickly discharge capacitor c5 after the power supply is disconnected, and voltage regulator tube VD1 is used
for the DC voltage at the output end of the power amplifier , so fluctuations in the power supply circuit will not affect the quality of audio playback. Another feature of this circuit
is that it can work in an ordinary single-channel state, such as listening to language programs. In this case, the power consumption is reduced and the
lower limit frequency of the amplified signal is increased. At the same time, the switch SA1 is used to disconnect the speaker BL3 and the filter, and the speakers Bl-1 and BI-2
are connected through the capacitors C16 and C17, which weakens the signal with a frequency lower than 100Hz~150Hz. The BI_1 and BL2 speakers are also
connected through R17, C14 and R18c15, allowing signals with frequencies higher than 300Hz to pass through.