# Sixth Lichuang Electric Competition# Desktop small power amplifier

* 1. Introduction to project functions

• Using 3.5mm audio input
• NE5532 pre-amplifier TPA3118 post-amplifier
• The rear output is equipped with XD3915 audio light
• The preamp can be switched to NE555 electronic keyboard
• The power supply adopts ch224k decoy 12V

You can usually plug in the 3.5mm and use it as a small speaker, or it can be used as a small electronic keyboard, which is relatively portable.

*2. Project attributes

* 3. Open source agreement

*4. Hardware part

The audio signal can be tested with a multimeter in AC mode (the mobile phone outputs about 0.5V and reaches about 1.5V through the op amp)

If the front stage is normal and the rear stage has no output, you can check whether the chip is soldered properly.

TPA3118 has a no-load input of 3V and an output of 6V. If used with the audio light, the best voltage range is 6~VBUSV (otherwise the light will be always on)

The 18W charger does not provide enough power to start the electronic keyboard and op amp at the same time (it will repeatedly apply for 12V)

The noise floor is somewhat loud and will cause great interference if it touches the switch potentiometer.

After startup, if the output current is very large, it will power down to 5V and reapply for 12V.

It should be better to use 9V for VBUS

Below is the actual picture

*5. Software part

none

*6. BOM list

CH224K potentiometers were purchased from Taobao

*7. Contest LOGO verification

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

Lichuang Electric Competition: "Desktop Small Power Amplifier"-Power Amplifier Function Demonstration

Lichuang Electric Competition: "Desktop Small Amplifier" - Electronic Keyboard Function Demonstration

[Desktop small power amplifier-Bilibili] https://b23.tv/ojMQY7