# Sixth Lichuang Electric Competition# Low-cost 2-channel audio amplifier based on LM1875

 1. Introduction to project functions

This design is a dual-channel OCL power amplifier with a tone front end, based on the LM1875T Class AB power amplifier IC design. In the audio DIY circle, LM1875 has always been an immortal epic legend IC - you can often hear people saying that the voice of 1875 is soft, bold, sweet, etc. I won’t go into details here ~ In short, the two 1875s here control two an independent channel. The front end is equipped with two attenuators for treble and bass, which can more conveniently highlight the expressiveness of music in a certain frequency band.

*2. Project attributes

This is an open source, first public project, designed by me.

* 3. Open source agreement

This project is open source using the GPL v3 protocol, and the original author retains the right to authorize it.

*4. Hardware part

This picture shows our preamp input, where the two WH148 potentiometers are our treble and bass adjustment knobs. C3, C4, C12, and C11 have established low-pass filter LPF for two channels respectively. C5, C6, C10, and C9 have established high-pass filter HPF for two channels respectively. Their outputs are connected in series with a capacitor to isolate the interference of the later stage. . Then the outputs of the two are connected to the next stage's power amplification stage with twenty times the power.

At this stage is a typical non-inverting operational amplifier circuit. The output capacitor and resistor connected in parallel can eliminate low-frequency oscillation for us.

The two 1uF capacitors in the negative feedback can stabilize the zero potential of the op amp output. We can try to short-circuit them later. If the potential drift does not exceed ±30mV, it can be omitted, which can help improve the sound quality.

There will be a light BUFF easter egg in the Logo ~ Wait for the board to be received

--The lighting part was laid with copper by mistake. As a result, the lights cannot be seen/I cried to death.

**All hardware parts are designed using the great Lichuang EDA

*6. BOM list

Note: BOM list involved in the project. Please upload a screenshot of the BOM at this location. Please upload the list details in PDF format to the attachment. Suggestions include model, brand, name, packaging, procurement channels, usage, etc. The specific content and form should be based on clearly expressing the project composition.

*7. Contest LOGO verification

* 8. Demonstrate your project and record it as a video for uploading

Video requirements: Please shoot horizontally, with a resolution of no less than 1280×720, in Mp4/Mov format, and the size of a single video is limited to 100M;

Video title: Lichuang Electric Competition: {Project Name}-{Video Module Name}; such as Lichuang Electric Competition: "Autonomous Driving" - Team Introduction.

More details: https://diy.szlcsc.com/posts/06c94d90c2c447dfbd9ed7339ff4a5b1