Digital audio amplifier with PLL synthesized FM radio

This is high quality stereo digital audio amplifier with PLL synthesized FM radio receiver. Some of the high level specifications of this receiver are listed in below:

  • Audio output power: 4W + 4W (with 8ohm speakers)
  • Input sources: FM and 3 external stereo line inputs
  • FM frequency range: 88.00MHz – 108.9MHz
  • Supply voltage: 12V – 15V (2A current source is recommended)
  • Tone control options: Bass, Treble and Loudness control
  • Bass / Treble boost: 14dB
  • Bass / Treble cut: 14dB
  • Station memory: Preset 10 FM radio stations
  • FM tune options: Auto and Manual with 25 kHz steps
Key components of this audio system are ATmega32A - 8bit microcontroller, TT502 (TEA5767) stereo FM radio module, PT2314 audio processor and μPC2002 audio power amplifier. This system is design to work with 12V - 15V (2A) DC power source and KA7632 multi-output regulator is used to manage power requirements to the above mentioned components.

Prototype version of digital audio amplifier

User interface of this system consist with 10 push buttons and 16 × 2 character LCD module. All the analog components of this receiver (including power supply) are controlled by ATmega32A microcontroller.

To get the best audio experience we recommend to couple this system with 8Ω - 8 inches (or higher) full range speaker system. In our prototyping stages we try this system on breadboards and hand-made PCB, and get equivalent results. All the power ICs (μPC 2002, KA7632) and transistors (IRF9610, TIP32) need good heat sinks.

The FM radio receiver in this system is based on Samsung TT-502X PLL tuner module. Internally this tuner module use TEA5767 PLL tuner IC and all the communications between this module and microcontroller are happening through TWI (I2C) bus. Pin outs and PCB layout of TT502 is different from commonly available TEA5767 radio modules and this module is common available to purchase and it is originally used by Samsung portable digital audio players.

Samsung TT-502X PLL tuner module

This project consists with several power, audio, RF and data lines, because of this, proper PCB or wiring layout is essential. All the digital components of this system are operating at 3.3V. Most of the analog components excluding FM tuner are operate above 7V. For optimal results proper isolation (less interference) between audio lines and data lines (I2C) are necessary. When wiring this project take special care about analog and digital grounds used in this system. Ground loops may leads to noises and oscillations in the audio output. We are recommending screen wires for both audio and antenna lines.

In our prototype we use home-made adapters with PT2314 and TT502. Layouts of those adapters are available with the project package (as EAGLE component library). The prototype PCB layout, which we are using is designed by hand and because of that it is not available with the package.

TT-502X pin connections

Firmware of this system is written using MikroC for AVR. All the project source codes and compiled binaries are available with the project package. When installing the new firmware, erase microcontroller EEPROM and set its all bytes to 0xFF. This setting may install new configuration profile to the microcontroller EEPROM at the initial system boot.

As described in above all the power ICs and power transistors need sufficient heatsinks. Do not mount IRF9610, TIP32 and KA7632 on same heatsink. Both μPC2002 ICs can share same heatsink and it is recommended to connect μPC2002 heatsink(s) to ground.

This project is an open source hardware project and all the contents are available to download at google drive. All the source codes and designs in this project are release under the terms of MIT license.