This article introduces high quality digitally controlled 2.1
channel analog audio power amplifier system. This project is mainly
based on TDA7377 AF power amplifier and PIC18F452 8bit
microcontroller. Basic technical features of this receiver are
covered in table1.
This unit is specifically design to work with PC sound cards, radio
receivers and CD/DVD/Blue-Ray players.
This system use commonly available electronic
components and substitute components can also use.
For maximum quality we recommended to use components
from same manufacturer. For example some actual
capacitor values and resistor values are slightly
varied from manufacture to manufacturer, and this
cause some minor unbalances in output of amplifiers.
When soldering the PCB we suggested to soldering
small components such as jumper wires, resistors
first and moving to larger components at last.
Also try to use IC sockets for all the DIP and
TDA7377 ICs. In our prototype all the integrated
circuits except 2 voltage regulators (IC5 - 7805 and
IC6 - 7808) are connected to mainboard via IC
sockets. All the controls, I/O and power terminals
and display modules are connected to mainboard
through wires, and for control and display lines we
recommended to use suitable ribbon cables. For power
and output wires 18-20 gauge multi-strand cables are
recommended (these wires are commonly used for
automotive wirings). In given PCB design 4 wires
need to be installed for I2C bus and MCU STAND-BY
lines. For this, standard Teflon coated 32-30 gauge
wires are sufficient.
Microcontroller firmware and source code
This project is an open hardware project and all the
source codes of PIC18F452 MCU are available to
download at project website. The source code of
PIC18F452 is written using MikroC for PIC compiler
and free version of this compiler is available to
download at Mikroelektronika home page. Currently
available firmware is design for 8MHz clock and
other required MCU related settings are listed in
table 2. Compiled HEX file for PIC18F452 is also
available to download at project website.
: Mikroelectronika home page is
http://www.mikroe.com. MikroC for PIC is
available to download at
After assembling the system it is necessary to check
all the power connections are working properly in
this system. To check power lines follow the steps
1. Connect both AGND and DGND together and from here
onwards this connection is referred as GND.
2. Unplug TDA7377, TDA7315, LA2650, PIC18F452 and
1602 LCD module from the mainboard.
3. Disconnect any audio inputs and outputs.
4. Supply 12V – 14V DC input to GND and V+ lines.
5. Check the voltages between IC pins which are
listed in table3.
If voltage readings are correct, plug all the ICs
and LCD module and hold down the SYSTEM-RESET button
and apply power to the system. While holding the
SYSTEM-RESET button press.
POWER ON/OFF button and turn on the system. Once you
got the LCD on, release the SYSTEM-RESET button and
adjust the controls and check the audio outputs.
After firmware update or at initial run, pressing
the SYSTEM-RESET button is essential to avoid any
damages to speakers due to high volume levels.
The most common problem can occur in this amplifier
system is no audio from the power amplifier IC. The
most possible reasons are excess supply voltage
(which is above 18V) or short circuits in output
terminals of amplifier. TDA7377 is equipped with
several protection features and state of the
protection system can be monitored through Pin 10 of
Second most common issue is LCD with 16×2 boxes.
This occurs due to initialization problems of
HD44780 controller. A common reason for this issue
is wrong wiring or faulty PORTD outputs.
If LCD output is too light (or dimmed), change the
value of R1 (2.2KŮ) resistor. We set this value for
commonly available Blue/White 1602 LCD module.
PCB bottom layer
Download full article
Download Eagle Schematic and