The ALC5686 is a highly integrated USB audio CODEC specifically designed for high-quality USB Type-C headphones and related audio devices such as USB to 3.5mm audio jack adapters. The chip is characterized by its versatility and powerful audio features, making it an ideal choice for modern audio applications. As there have been many questions about this topic and this mobile chip in particular, I have summarized the most important points today and will also draw a comparison with the ALC 4080, which has already been described several times. However, I have to put the brakes on the euphoria right from the start, because such 10-euro adapters cannot even come close to replacing a good DAC. They simply lack the higher output power. But as a supplement for various mobile devices, the parts are really good.
The ALC 5686 in detail
The ALC5686 combines several innovative functions, including a USB 2.0/ADC 3.0 digital audio interface, I2S and I2C interfaces and an integrated flash memory that saves space on the circuit board. It also features high-quality hi-fi headphone amplifiers with a signal-to-noise ratio (SNR) of 124 dB and a total harmonic distortion (THD N) of 95 dB. These features ensure longer battery life and a premium listening experience.
The chip also offers an advanced jack detection function that automatically distinguishes between headsets (4 segments) and headphones (3 segments). Support for CTIA and OMTP standards, along with automatic detection and adjustment of microphone and grounding signals, is also integrated. An automatic impedance measurement that recognizes the connection resistance in nine steps from 0 Ω to over 50 kΩ is another highlight. The ALC5686 is particularly suitable for USB or USB Type-C headphones and headsets as well as USB or USB Type-C audio accessories.
Key features
Key features of the ALC5686 include:
- USB 2.0 interface: Supports both full-speed and high-speed modes, with audio support up to 32-bit and a sampling rate of 8 kHz to 384 kHz.
- Energy-saving mode: When the socket is not plugged in, power consumption is less than 100 µA.
- Integrated flash memory: 256 kB embedded memory facilitates configuration.
- High-quality headphone amplifier: The Class G amplifier offers SNR values of up to 124 dBA and a THD N value of -95 dB at a load of 32 Ω.
- Flexible microphone inputs: The amplifier supports multiple gain levels (up to 52 dB) for optimal recording quality
- Multifunctional interfaces: The chip has a master I2S interface with a maximum sampling rate of 48 kHz and an I2C interface with a clock frequency of up to 2 MHz.
Structure and function
Functional blocks
The ALC5686 has a modular design with separate blocks for analog and digital signal processing. The analog components include an audio mixer, a headphone amplifier and several microphone preamps. Digital processing includes ADCs, DACs and a USB 2.0 controller.
Power supply
A highly efficient DC-DC step-down regulator ensures a stable power supply with input voltages between 3.0 V and 5.5 V. The efficiency of the regulator is between 80 % and 85 % depending on the load, which minimizes the chip’s energy consumption.
Audio mixer
The analog mixer enables flexible audio paths with adjustable gains and digital filtering. The digital mixer offers additional options such as 12-band equalization and automatic noise reduction.
Electrical characteristics
The electrical characteristics of the ALC5686 are impressive:
- Maximum input voltage: Up to 5.5 V at the microphone inputs.
- SNR and THD N: Excellent values for both the headphone and microphone inputs.
- Crosstalk: Minimum crosstalk of -100 dB at 32 Ω load.
Comparison between ALC5686 and ALC4080
The ALC4080 is another well-known audio CODEC from Realtek that focuses on high-resolution audio playback. Both chips are quite powerful solutions, but there are significant differences in their application areas and technical specifications. The ALC4080 outperforms the ALC5686 in terms of pure sound quality, as it is optimized for high-resolution audio applications. With a signal-to-noise ratio of 120 dB and a dynamic range of 110 dB, the ALC4080 delivers exceptional fidelity. The ALC5686, on the other hand, is designed for use with mobile devices and offers excellent performance with low power consumption.
The ALC5686 is significantly more energy efficient and optimized for battery-powered devices. Its integrated DC-DC converter maximizes power efficiency, while the ALC4080 is often used in desktop or stationary applications where power consumption is less critical. Both chips have a USB 2.0 interface, but the ALC4080 additionally supports digital audio formats such as DSD (Direct Stream Digital) for audiophiles. The ALC5686 focuses on compatibility with headsets and mobile audio devices, including advanced jack detection.
The ALC4080 is better suited for high-resolution audio playback in PCs or Hi-Fi systems, while the ALC5686 is designed for mobile applications and use in USB Type-C headsets. This specialization makes the ALC5686 more flexible for portable devices, while the ALC4080 is a better choice for stationary use.
Conclusion
Realtek’s ALC5686 is a versatile and powerful sound chip with interesting features and efficiency suitable for a wide range of modern audio solutions. The integration of numerous functions and the support of various standards make the chip an ideal choice for developers of more affordable audio devices. Its robust performance characteristics and energy efficiency make it a solution for high-quality but affordable mobile audio applications. A comparison with the ALC4080 shows that both chips offer specific strengths for different application areas, with the ALC5686 being particularly impressive due to its versatility and energy efficiency in mobile use. But as I wrote at the beginning: it won’t be able to replace a good DAC with a powerful headphone amplifier.
I have also attached the complete data sheet on the next page for the very curious and inquisitive among you and added the articles on the other models as links, so please turn the page!
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