Published December 15, 2025 © GPL3+

Control BASS, TREBLE, MID and VOLUME with a lot of equalizer modes, all in a small PCB with WIFI, include PCB and code.

IntermediateFull instructions provided2 hours**1

Things used in this project

Story

In a pretty recent tutorial we have discussed PT2258 based 6 channel tone controller. I have used it as a preamp for the amplifier and controlled all the 6 channels through ESP on a web server. Today we have PT2315, a two-channel digital audio processor. It is a full fledged DSP with functions to control: Volume, Bass, Treble and Balance. Loudness Function is also provided to build a highly effective electronic audio processor having the highest performance and reliability with the least external components.

All functions are programmable using the I2C Bus. The pin assignments and application circuit are optimized for easy PCB layout and cost saving advantage for audio application. Housed in a 20-pin DIP/SOP, PT2315 is pin-to-pin compatible with TDA7315 and is very similar in performance with the later. Although the full digital system may have some disadvantages because everything is based on an IC and some external components, the flexibility to work with this system decreases on the hobbyist end.

This type of IC is used in surround sound-type things, Here with the two channel volume we can also control equaliser. And you will see how we made our custom equaliser mode and deployed everything on a web server. Some of the listed features of PT2315 are:

• Least external components
• Treble and Bass control
• Loudness function
• Input/output for external noise reduction system/equalizer
• 2 independent speaker controls for Balance function
• Independent mute function Volume control in 1.25dB/step
• Low distortion
• Low noise and DC stepping Controlled by I2C bus micro-processor interface
• Pin-to-pin compatible with TDA7315

Components Required:

• PT2315
• ESP12E/ESP8266
• 2.2uf/47uf/10uf electrolytic capacitors
• 2.7nf/100nf ceramic capacitor
• 2.2K/5.6K/10K resistors
• 3.3V AMS1117 regulator
• Some pin headers
• 5V power source

Circuit diagram:

I have taken the reference from the circuit given in the datasheet. Here, you can see that the IC has 2 channels. We need 2 inputs and 2 outputs.The input is directly fed without referencing ground but using a 2.2 μF coupling capacitor in the signal path. The output resistance and coupling together behaves like a filter arrangement. Because the circuit is fixed, the only controlling input to the IC is the I2C bus, allowing us to connect any microcontroller.

Now, here is the circuit diagram I used for the IC. Since we have only one I2C bus, the ESP8266 supports this protocol, and it has Wi-Fi, so we can utilise these features. There are a lot of revisions you will find on the internet using the same code and libraries for this DSP. But now with this microcontroller and web server, we have eliminated a lot of components. No need to print the data on screen, and no need for external push buttons. However, there is always an option to do this because most of the microcontroller’s GPIOs are available.

PCB Design:

I want to keep the system minimal, the reason is that there are analogue and digital parts that are on the same circuit board, and the data is travelling through SCL and SDA lines. The audio is not such a high frequency, but we should follow proper guidelines. The best thing is to route these digital signals away from any analogue signal and surround them with ground planes.

For the assembly, because I have used mainly the THT components, which can be soldered by hand, moreover, only the ESP8266, 3V3 regulator and PT2315 are using SMD pads, where you may get some issues. Still, I always recommend soldering the SMD first, then moving to the THTs, and finally to the header part. In this way, with minimum time and effort, you can solder this board. All the links to FILES: GERBER/BOM/CPL are here.

The same is implemented here in the design; I use ground fills on both layers, which can be connected with vias and ground stitches. Moreover, the LDO is in the middle, powering the ESP8266, and all other systems run at 5V. The signal may get interference if the supply used is SMPS, so try to go with batteries or a good power adapter with EMI shielding to reduce the overall noise. The PCB features programming headers on the bottom layer, where all connections are made to another ESP8266, allowing for programming to be done. To see the step-by-step programming tutorial, please refer to this link.

Taking the Project to the Next Level - With JUSTWAY

Electronics without proper housing and the audio circuit, they simply would not work. Yes! Because to keep the system available to us a proper 3D casing should be there. JUSTWAY assists you in turning your do it yourself project into a high-quality prototype that feels and looks like a genuine product that is ready for the market. What they do:

• Rapid Prototyping
• CNC Machining (Aluminum 6061 / Stainless Steel 304)
• Sheet Metal Fabrication
• Injection Molding
• Urethane Casting
• 3D Printing (SLA & HPA-PA12)

Just 4 Easy Steps to Order: Upload your CAD files at JUSTWAY.com, Select the material & finish then preview your model in 3D and place your order.

Code:

We can program the ESP through Arduino. A complete tutorial for this is already shared on my profile. In this code, we are utilising the basic Arduino libraries. These libraries can be downloaded from the Library Manager, located under the Tools menu in the Arduino IDE. The <WiFiManager.h> library is the one which is responsible for setting up the WiFi.

#include <Wire.h>#include <EEPROM.h>#include <ESP8266WebServer.h>#include <WiFiManager.h>  // Include WiFiManager library#define PT2315_address 0x40#define EEPROM_SIZE 10ESP8266WebServer server(80);

The address of I2C is given here, you can choose one from the programmable address. Because my hardware is designed specifically according to this one hence using the same.

// ===== I2C Functions =====void writeWire(byte a) {Wire.beginTransmission(PT2315_address);Wire.write(a);Wire.endTransmission();}

The complete code is shared below, which I am using for this tone controller. The section shared above is the I2C transmission, which sends the data to the PT2315. The programming is done in a manner that requires no external libraries and is extracted directly from the datasheet, keeping the working process minimal and fast.

Web Server Setup:

It is the HTML-coded part in the programming section, where all the GUI and I2C logic is implemented. After uploading the code to the ESP, open your mobile phone WiFi and connect to AudioConfigAP.

It will open a webserver through which you can connect to available WiFi in that range. After the successful connection message is displayed on the serial monitor.

Connecting a network:

And finally give you an IP address. After opening this IP in the browser connected to the same network, you will get this interface:

Server GUI:

Video:

Here is the proper video, with a step-by-step guide to setting up the WIFI and web server:

POP noise:

When turning on the system, due to line interference, this noise can enter the system. When changing the settings on the web server, the POP issue may occur if the amplifier you are using does not have proper input circuitry. Using the tweeters with this system is a terrible idea, but I only have them aligned around, hence pairing them.

Closing:

It is just a tone controller, but the interesting thing is the 2 channels with all the equaliser modes, all can be controlled through the server. The file code and PCB have already been tested, and the process is also shared in the video above. And if you like the concept, please comment below for more ideas and checkout the Justway for 3D printing and moulding services.

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