After seeing the super-heavy bass amplifier made by LM3886 published in the studio on the whole network, I saw it and used NE5532 to process the bass. This is really a good choice. NE5532 has long been known as the "empire of the op amp" Bass pre-processing is really cheap.
So, I did some research on this circuit, but there is a problem but I do n’t quite understand why it is necessary to connect the non-inverting input terminal of the op amp and its output terminal to the inverting input terminal. What about the small resistance? And there is such a large capacitor between the non-inverting input and ground.
Confused, I copied one according to the circuit, connected the power supply and the speaker, and connected the CD source. But it was found that there was only porch sound in the speaker, and I checked the circuit again, and found that there was no problem, so I concluded that the circuit itself was defective. But where is the problem? Checking the circuit diagram, I focused on the op amp again.
Analyzed here, the first stage of the op amp uses the in-phase input mode, and the latter stage is the inverting input mode. The amplification ratio of the first stage is 1: 1. The low-frequency signal is formed by combining the L and R signals. After the low pass, it is sent to NE5532 for first-level in-phase amplification, which is equivalent to "shooting with". After the pin 1 is output, it is sent to the post stage. Here, the circuit is simple and traditional, but there is a problem with the amplification of the post stage. Here the signal is directly sent to the inverting input terminal, and the input terminal directly reaches the 7 pin output terminal. "Shooting" method, so what is the second-level op amp doing here? In more layman's terms, the second-stage op amp is in a "half short circuit" state. How can it work normally? Even if it is corrected, it is normal, but as long as anyone who has used the LM3886 knows, its amplification ability is extremely limited. This is the result of exchanging high-quality sound quality. If both low-frequency amplifications are used When the 1: 1 amplification is added, and when the L and R channel bass are combined, an isolation resistor of 100K is added. How can such a small signal drive the LM3886?
The author believes that the following improvements can be made: the second-stage op amp can be set to the in-phase input mode, the connection between the NE5532 pin and the 6 pin can be removed, and the 6 pin of the op amp can be grounded with a capacitor (or not connected), but this still There is a problem of insufficient driving force. This can add a resistor between pins 6 and 7 of the second-stage op amp to increase the gain. The gain can be set manually. It increases with the increase of the added resistance However, the resistance of the two channels combined with L and R cannot be changed, which will affect the separation of the stereo.
After the modification, the bass is sufficient, there is a real bursting effect, and the sound field is much wider. This should be regarded as a good bass amplifier. (Thank you Mr. Wang for supporting this site) December 15, 2004 ----- Webmaster Technical area detailed analysis of Doherty power amplifier design load traction principle (top) detailed analysis of Doherty power amplifier design how to improve efficiency (lower) voltage follower input and output error analysis lm386 power amplifier energization will produce noise causes and treatment methods analysis class d Solve the effect of power amplifier on emi  Follow WeChat Interesting and informative information and technical dry goods  Download Audiophile APP Create your own personal electronic circle  Follow the audiophile class Lock the latest course activities and technical live broadcast Collect People collection share it: ![]() '+ data.username +' |