Homemade current negative feedback electronic frequency dividing power amplifier 02

The electromechanical schematic diagram is shown in Figure 5·1 1 2. The picture is a circuit diagram of a sound channel.
    As can be seen from the picture, the whole circuit is very simple. It consists of the following parts:
    (1) Electronic frequency division part 6 ICl is the NE5532 port known as the "King of Op Amp". It and the surrounding resistor-capacitor components form
a typical active second-order filter 6 input After the signal is divided, it enters the rear power amplifier unit for amplification. According to the data in the figure
, the frequency division point of this filter is 3. 7kHz. If it needs to be changed, just simply calculate and change the RC components of the filter.
    (2) The core IC3 of the power amplifier part is TDA1514. lC4 is LM1875. They are responsible for the amplification of low, medium and high frequency bands respectively.
It can be seen that the biggest difference between this part and most power amplifier circuits is that it adds a negative feedback circuit p. The feedback form used by general power amplifiers
is voltage negative feedback, while this machine uses current negative feedback. R15. R23 samples the current flowing through the speaker
and feeds it back to the input of the amplifier, so that the amplifier drives the load with a fixed current. In this way, the speaker also becomes
a part of the negative feedback network, which can eliminate the impact of the speaker impedance on the transient characteristics of the electroacoustic system,
minimizing the transient distortion of the system, thus improving the sound quality. In addition, after using current negative feedback, the output power of the power amplifier increases as the load impedance
increases, which is similar to the output load characteristics of the tube