# Sixth Lichuang Electric Competition#30W Bluetooth 2.1 channel power amplifier (verified)

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Please fill it out during the registration stage↓

* 1. Introduction to project functions

Based on the Class D digital power amplifier chip TPA3116 Bluetooth power amplifier. Bluetooth uses BK3254 module.

1. Support 2.1 channel.

2. Supports two audio source inputs: wired 3.5 and Bluetooth, which can be switched at will.

3. Support USB and TF card playback.

4. Three types of adjustments: total volume, stereo, and bass.

5. The power amplifier and Bluetooth use B0503S power isolation module, which effectively avoids current sound in different places.

6. The Bluetooth BK3254 module also has FM, infrared remote control and other functions. It is not used in this work. Interested friends can join it.

The speaker was modified from an idle 5.1 center speaker at home, replaced with a new 30W 4-inch full-range speaker + a 4-inch woofer, and an empty box was purchased for the woofer.

Tested both active and Bluetooth audio sources perfectly. The bass is strong enough. Since it uses 12V power supply, it will basically not reach full load power (the maximum output power under different voltages is different, the higher the voltage, the greater the maximum output power), but this set is enough to cope with 4-inch 30 watts. If possible, you can install 6.5-inch speakers + 8-inch bass!

The video was shot with a mobile phone, the quality is average, and the recorded sound is definitely not as good as the real thing. I didn't dare to turn up the volume, just a little. Don't dare test the maximum volume! Afraid of disturbing the people!

The left and right channels use a piece of NE5532 + a piece of TPA3116D2 to form the front and rear stages. The current magnification of the front stage is about 11 times, which feels pretty good! The magnification speed is determined by R21, R22 and R23, R24. Formula: Magnification A=1+R22/R21

The bass channel uses two pieces of NE5532 + one piece of TPA3116D2 to form the front and rear stages. One NE5532 is used as a bass amplifier, and one NE5532 is used as a low-pass filter. The rear stage is connected in PBTL single mode, and the theoretical output power can be up to 100W.

Of course, there are still areas worth improving. For example, the NE5532 can use a voltage stabilizing module to stabilize the voltage at 12V-15V, so that it can be powered by conventional 18V and 24V power supplies. Currently, the temporary use of 12V power supply will cause the voltage of NE5532 to be lower than 12V. Another example is that you can use dual power supplies if conditions permit. But the internal resistance must be symmetrical and the voltage must be stable!

There is not much to say about the power stage TPA3116D2. It basically follows the data sheet, except that the filter capacitor is increased.

In addition, it is best to use 22uH inductor, because the low-pass cut-off frequency of 22uH+0.68uF is 41.15kHz, and the low-pass cut-off frequency of 10uH+0.68uF is 61kHz, so theoretically the performance of 22uH+0.68uF is much better than that of 10uH+0.68uF. Moreover, the quiescent current is also lower than 10uH+0.68uF, and the heat generation is also low. Therefore, I am going to switch to a 22uH inductor and experience the difference (I will update my experience later).

Regarding TPA3116D2 gain (pin 8): You can refer to the data sheet.

But the general principle is: when the gain of the power amplifier is set large, the input noise will be amplified together, and the output noise floor will definitely be very large. It is generally recommended that the gain can be appropriately larger when the supply voltage is below 12V, and it is not recommended to use a large gain when the voltage is above 12V. That is, if you feel that the noise floor is too loud, you can try adjusting the gain.

Regarding Bluetooth: Using the BK3254 module, currently only USB and SD are lead out. As for FM, etc., they are not needed for the time being, so they are not lead out. The serial port function is retained (the Bluetooth name can be changed).

                  The power supply module uses B0503S to isolate the common ground. To avoid the common ground current sound generated by Bluetooth.

PCB Layerout: The source of the left and right audio channels to the front stage, and the front stage to the rear stage should be differentially and equal-length wiring (I suddenly thought of it, but I forgot it when I drew the picture. There is no problem after making the board, but the best differential length is equal)

                         The power supply and output are copper-plated and bold.

Note: There is no limit to the theme. It can be a solution to a certain problem in life/work, a plan designed for a certain group of people/scenarios, graduation project/course design/DIY project/purely cool project, etc. Mainly talk about what problems you solved by what means.

*2. Project attributes

This project is made public for the first time and is original!

Note: Please indicate whether the project has been made public for the first time; whether the project is original; whether the project has won awards in other competitions; if so, describe the details of the award; whether the project has participated in a defense in school.

* 3. Open source agreement

GPL 3.0

Note: Altruism means self-interest, please read the following content carefully.

1. Embrace open source and give projects unlimited value. It is recommended that more than 80% of the core functions of the project be open source;
2. If a certain part of the function is irreplaceable and the project cannot solve the corresponding problem after deletion, then the function implemented by this part is the core function of the project; for example, if an electronic load is designed and a host computer software is designed to monitor power changes, the electronic The load is the core function, and the host computer software is the auxiliary function; for example, an isolated 485 module is used in the electronic load to communicate with the host computer, then the communication function implemented by this 485 module is an auxiliary function;
3. Projects should choose an open source agreement that suits them . If the project references other open source projects, the source should be indicated and follow the original author's open source agreement. It is recommended that original projects use the GPL3.0 open source agreement;
4. Functions implemented by directly quoting the original circuits or original codes of open source projects cannot be used as the core functions of one's own projects, and functions directly implemented using common modules on the market cannot be used as core functions of one's own projects.

Please fill in during the competition stage↓

*4. Hardware part

Note: It is recommended to use Lichuang EDA . If you choose other EDA tools, please upload schematics in PDF format, PCB drawings in PDF format, and PCB files in Gerber format in the attachments. Here you can explain in detail your project implementation principles and mechanisms, precautions, debugging methods, testing methods, etc. It is recommended to introduce your ideas to others in the form of pictures and texts.

*5. Software part

none

Note: If your project involves software development, please upload the corresponding project source code in the attachment. Here you can describe in detail your software flow chart, functional module block diagram, explanation or popular science of related algorithms, source code structure, construction and configuration of compilation environment, source code compilation method, program burning method, etc. It is recommended to introduce your ideas to others in the form of pictures and texts.

*6. BOM list

Reference schematic

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

Please upload a project picture containing the competition logo. The logo will be printed on the PCB in the form of silk screen printing.

Click the zip to download the competition logo! (Contest logo).zip

* 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