A power amplifier circuit created with LM1875 + NE5532, LM1875 Power Amplifier
Keywords: A power amplifier circuit made with LM1875 + NE5532
A power amplifier circuit (suitable for multimedia active speaker upgrade) with LM1875 + NE5532
Be
LM1875T is an audio power discharge integrated circuit introduced in the 1990s of the National Semiconductor Company, using TO-220 packages, less peripheral components, excellent performance, and fast frequency response and fastness, from the beginning of the 1990s Recommended by the vast audio enthusiasts now. The most valuable thing is that the price has dropped from the original ten dollars to the present eight nine yuan, and it is best for money that I don't want to spend too much money and think about fever hidden love amateur production. The most advantage of this IC is that the sound quality of the small power output can directly and the listening effect of high-end sounds,
At the standard operating voltage, the average power can be obtained, which is sufficient in general home conditions, the author used the NE5532 pre-tone circuit to promote the success, just like the various e-newspapers and magazines, it has achieved excellent results, unfortunately Such a high-profile integrated circuit is rarely used in the commercially available amplifier and multimedia active speakers. Although the appearance of how the appearance is pleasing and delicate, open the housing, it is difficult to find its aramid, but the manufacturer in order to The cost of saving those yuan, mostly uses a cheap circuit such as 2030 or other names, because the TDA2030 is completely, can directly replace it, can get immediate results, but must be genuine. The following is the application of the electromechanical map, just draw a channel,
Circuit principle:
Be
Be
Only one channel is drawn above and the other has the same principle.
JP1 is an audio input, and the coupling capacitance is eliminated here because the current source CD, VCD, DVD, TURN, computer sound card, etc. are basically output, and the U2 and the previous sealing element composition feedback. Tone circuit, U1 is a prodrier linearly magnification, set to 2 times magnification. It can be changed according to the actual situation, R18, C13, C14 is the power isolation filter portion to reduce the two-stage mutual string, DW1, DW2 is a regulator tube, if the power converter is double 12V, Go to it,
Advanced power amplifier section: In the past e-newspaper, it is often introduced to the power amplifier integrated circuit to cancel the negative feedback capacitance, plus a DC servo circuit composed of an operational amplifier, so that it becomes a pure DC power discharge circuit, and the facts are LM1875, and LM3886 Wait, don't need more this, directly cancel the capacitance, actually measure the output with the digital multimeter, found that its zero offset is very small, only a few millivolts, I use such a circuit for many years, I have not burned the integrated block and The incident of the speaker happens, and the integrated circuit has an overheated overflow protection function. In the circuit, the lower negative feedback capacitance in the negative feedback circuit has turned into a fixed flow amplification circuit, which greatly broadens the frequency response, and the fact proves, As long as the previous audio input capacitors are selected, it is generally used with CBB 1U, or with other fever brands such as WiMA, the post-stage potential is very stable, and cannot be used in general electrolytic capacitors, because there may be small current through, by zooming After the post-level unstable, you can use the sound quality of the cancellation of the sound quality, especially the high-frequency and bass broaden, the circuit cancels the usual use of the op amp to do servo circuits, making it easy to make the production .
In addition, the circuit also adopts a current negative feedback circuit. The circuit is also recommended for many circuits recommended in recent years. Compared to the voltage negative feedback circuit, its gain increases with the increase of the increasing output current, which makes low frequency playback Strengthening, it is necessary to point out that when using this circuit, the power reserve of the power supply has a margin, which is recommended to use 150W of loop. Otherwise, not only does not reach the expected results, but make distortion increase, if your power transformer has little power, it is recommended that you use traditional voltage negative feedback.
Below is the front-rear ranking plate image with two LM1875T and two SIG NE5532 (large s). An op amp is a negative feedback tone, and the other is a linear buffer, and the PCB design is grounded separately from the front and rear ground, a little grounding to better play the excellent performance of the integrated circuit, including power rectification, connection, As long as you access the transformer power cord, you can work.
The following is a PCB map
Be
Element selection and audition:
The capacitive portion is the German red WiMA capacitor. The NE5532 is authentic SIG production. The power filter electrolysis is Nichicom 25V / 4700UF. The capacity is sufficient, and there is also a note on the pressure on the pressure. Since I use double 12 volt AC power supply, rectification The voltage after filtering is about 18V, which is sufficient to use 25V to resist, if the voltage of the power supply transformer exceeds 12V, it is recommended to use 35V / 4700UF, the resistance metal film, about the capacitor, here, there is an audio passage Sometimes it is essential but the impact on the sound quality is also a component, so there are many imported fever capacitors such as ELNA, such as the circuit, in this circuit, C2 and C5 selection, especially important (C5 is essential) The capacitance of the audio channel in this power circuit is only C10, which can be said to be a pure DC amplification circuit. So test the U2 output DC voltage is 0.9 V or so, there is no relationship, check the NE5532 information, which is much smaller than its maximum output voltage. LM1875 and NE5532 listening evaluation has a lot in the previous news magazine, no longer said. After assembled the above-mentioned power amplifier board, the individual believes that the LM1875 and NE5532 combinations, with its warm and delicate sound, there is also the advantages of high cost, very suitable for small rooms or households (especially multimedia computers), do not need too much Used in the case of loudness, use it for a long time to enjoy high-fidelity music will not feel the floating noise. This site will make PCB boards and finished boards after the LM3886 board, the relevant circuit will be slightly improved, and the PCB board will summarize the previous experience redestrian improvement, carefully select the components, and have smaller profits Maintain the purpose of this site to provide finished products and PCB boards to enthusiasts. Please contact your netizens.
Our other product:
