1.Project introduction

Amplify the input audio signal and apply it to audio and other equipment. You can also adjust each frequency band of the input signal to achieve a satisfactory listening effect.
See the equalizer: In addition to amplifying the signal, the LA3600 five-band audio equalizer
can also Music signal “visualization”

Using integrated IC, the whole circuit is very compact. The board size is 10*6cm and can be put in your pocket.

The pin header is for debugging. The pin header is defined as follows:

Input 12V power supply, can drive 10W speakers

Plug in the 9-18V power supply from the debug pin or power socket, plug it into the audio interface, adjust the volume of the input device to the appropriate level, and connect
the adjustable resistor next to the speaker adjustment port to control the sensitivity of the LM3915

This IC does not support volume adjustment, so it can be solved by directly connecting a potentiometer in series with the input end.

The non-inverting input terminal is connected in series with the signal with a 10uF filter capacitor to prevent noise.

The capacitor at the power supply end can achieve switching delay and prevent impact noise.

After this circuit is connected, the green LED will light up and will flash in color when there is a signal.

Equalizer introduction

The frequency band can be changed through the capacitance from Base and NF to the total NF terminal, and the level can be changed by changing the potentiometer.

The capacitance and frequency provided by this circuit are as follows

Input method: Insert the 3.5mm cable into the input terminal, and use the DIP switch to select the channel (left and right channels). The output channel is also output to the 3.5mm cable. You also need to specify the channel.

Only supports single-channel input or dual-channel mixed into single-channel input. If you want dual-channel, you can use the debug pin, which is defined as follows

Pin and female headers are optional, 1*10p

Plug in the 9-18V power supply from the debug pin or power socket, plug it into the audio interface, and adjust the input and output channels to connect to the power amplifier.

2. Project attributes

This project is an original project and is being made public for the first time. It will only be made public on the Lichuang open source platform.
It is prohibited from being sold as a commodity under the GPL3.0 agreement and is only for learning, education and other purposes.

This is a set of simple power amplifiers and preamplifiers. The sound quality and fidelity are not comparable to high-end power amplifiers, but it can be used in operational amplifiers.

3. Open source agreement

This project complies with the GPL3.0 agreement and is not for commercial use. It is only used for learning and education. Secondary creation is allowed, but after the second creation, it must be open source under the same agreement.

4. Hardware part

Balanced IC

To make up for the audio shortcomings, LA3600 five-band equalizer chip is added, using DIP-16 package.
Its center frequency and sensitivity are programmable
wide voltage input, which can withstand 5-15 volts without error and output
high stability capacitive load.

This is its pin definition

Base is broken and a capacitor is connected in series to the nf terminal,
and then a capacitor is connected in series to the potentiometer to the total reference terminal
to achieve center frequency adjustment.

If you want to achieve more segments of adjustment, connect the output terminal of the upper stage LA3600 to the input terminal of the next stage, and adjust C1 and C2 to adjust different center frequencies.

Center frequency calculation formula:

This part of the project: # Sixth Lichuang Electric Competition #LA3600 5-band preamp equalizer - Lichuang EDA open source hardware platform (oshwhub.com)

Power amplifier IC

TDA2003 provides 10W power amplification and clearly defined interfaces. It is more suitable for general desktop audio applications, with low cost and few peripheral circuits.

Level display IC

LM3915, provides 10-point logarithmic level indication, with 3dB per lamp, maximum +30dB range indication, the output current can be adjusted with a resistor (1,30)mA, wide voltage input range, and the display mode can be modified by modifying the MODE pin level (point shape, strip)

5. Software part

This project has no peripheral software

6. BOM list

According to BOM list

7. Contest LOGO verification

There is Lichuang Mall’s logo on the front and back:

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

see attached