ne5532 lm1875 power amplifier circuit diagram

ne5532 lm1875

LM1875T is an audio power discharge integrated circuit launched by National Semiconductor in the early 1990s. It is packaged in TO-220 and has few peripheral components, but it has excellent performance, wide frequency response and fast speed. It has been from the early 1990s Until now, it has been recommended by the majority of audio enthusiasts. The most valuable thing is that its price has dropped from a dozen yuan at the beginning to the current eight or nine yuan. It is most suitable for amateur productions that do not want to spend too much money and have a fever. The most important advantage of this IC is that the sound quality at low power output can directly match the listening effect of high-end audio,

The average power of 30W can be obtained under the standard working voltage, which is enough in the general domestic situation. The author used NE5532 pre-tone circuit to promote the successful release of the set, as various electronic newspapers and magazines have obtained excellent results, unfortunately Such high-profile integrated circuits are rarely found in commercially available power amplifiers and multimedia active speakers. Although the appearance is pleasing and exquisite, but it is difficult to find its Fang Ying when the shell is opened. Most of the cost savings of those few dollars are made with cheap circuits such as 2030 or other unknowns. Since the package is exactly the same as the TDA2030, you can directly replace it, you can get an immediate effect, but it must be genuine. The following is a schematic diagram of the application of electricity, only one channel is drawn,

In addition, this circuit also uses a current negative feedback circuit, which is also a circuit recommended by newspapers in recent years. Compared with the voltage negative feedback circuit, its gain increases with the increase of the output current of the stage, which enables low frequency playback Strengthened, it should be pointed out that when using this circuit, the power reserve of the power supply must have a margin, it is recommended to use a 100W ring transformer. Otherwise, not only the expected effect is not achieved, but the distortion is increased. If your power transformer power is not large, it is recommended that you use the traditional voltage negative feedback method.

The following is a picture of the front and rear power amplifier board using two LM1875T and two SIG's NE5532 (big S) as the front-end tone. One op amp serves as a negative feedback tone, the other is a linear amplifier. The PCB is designed with separate traces for the front and back grounds, and one point is grounded to better play the excellent performance of the integrated circuit, including power supply rectification, wire connection, as long as Connected to the transformer power line, you can work with electricity.

The PCB diagram is as follows:

Component selection and audition:

Maybe you can see at a glance that the capacitor part of the above power amplifier board is a German red WIMA capacitor, NE5532 is an authentic SIG product, and the power filter electrolysis is NICHICOM's 25V / 4700UF. The capacity is enough for the LM1875, and the voltage resistance is also It should be noted that since I use dual 12V AC power supply, the voltage after rectification and filtering is about 18V dual, so the withstand voltage of 25V is enough. If the voltage of the power supply transformer exceeds 12V, it is recommended to use 35V / 4700UF, and the resistance metal Membrane, about the capacitor, here is a mention, there are sometimes components that are indispensable in the audio channel, but also have a great influence on the sound quality, so now there are many imported fever capacitors such as ELNA that can be used in the circuit , The selection of C6, C7, C10 in this circuit is particularly important, here I have my own point of view, with the best fever capacitors, there are dielectric losses and phase distortions, but the degree of magnitude, then I can Remove it and remove it, then all the problems do not exist, would n’t it be better, also save the silver, just do it, just remove C6 and C7 (C10 is absolutely necessary) This circuit is not the province of WIMA 1UF), the results of the effect of greatly improved listening. The high and low frequencies are more natural and gentle, and the details in the sound increase a lot. In this case, fans can see that the capacitance of the audio channel in this power amplifier circuit is only C10, which can be said to be a pure DC amplification circuit. Then measure the DC voltage at the output of U2 is about 0.9V, no Relation, check the NE5532 data, this value is far less than its maximum output voltage. About LM1875 and NE5532 listening evaluation in the previous newspapers and magazines has a lot, no more.