In recent years, the removal of the traditional 3.5mm headphone jack from smartphones and other devices has led to the rise in popularity of USB-C to 3.5mm audio jack adapters. These adapters allow users to connect their favourite headphones or earphones to devices that only feature a USB-C port, offering a solution to the inconvenience of not having the headphone jack. However, before purchasing one of these adapters, there are several important factors to consider to ensure you make the right choice for your needs.
For this type of article – Best Earphone/IEM, DAC & Music Player for Samsung S24 Ultra, I often hear the complain – “my USB-C to 3.5 mm Audio Adapter is not working”. As for Samsung smartphones, I suggest purchasing their official converter. If that does not work then follow this guide – USB C Headphone/DAC Showing Up as Charging Device (Samsung). The same goes for Apple and other brands. You always need the official converter as your default converter device at least to test and troubleshoot the high-quality DACs.
Also, you may need to read What is USB Audio and How USB Type-C Audio Works and Understanding I²S: The Inter-IC Sound Protocol.
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USB C Audio will always output a digital signal. That is the specification. It is may not be an I2S protocol (that would be easy to design devices). We have to convert that “USB C audio” to I2S with one IC, and then add a DAC chip to convert it to an analog signal or may be extract the PCM audio.
It does not matter whether the unit is active or passive – the converter always needs at least this pair of ICs. In the case of active external converters/DACs, we can build advanced circuits by adding capacitors and other components. Also, we can add a microcontroller and instruct the DAC chip via serial connection. The total thing is complex since they wanted to avoid direct I2S output.
Samsung and Apple use IC from Cirrus Logic, which is more condensed and usually a 2-in-1 custom IC. While purchasing a third-party one, make sure that the manufacturers mention the DAC chip. For example ES9038q2m. The output will be 32-bit audio and support of DSD. There is almost no low-end alternative since ES9038q2m IC costs hardly $10 to the manufacturers.
A good converter will work with all devices including laptops with USB-C port (companies which follow the specification). HP Pavilion x360 14-cd0055tx works with Samsung’s USB-C to 3.5 mm Audio Adapter. I purchased that laptop with heavy discount during the pandemic.
I guess the implementation of the standard is not perfect or Android suffers from some sort of bug. This results “not working” situation. Overall, it would probably take 3-4 engineering man-years to implement a custom audio class USB device.
I know because I am trying to develop a cheap board based on ES9038q2m.
Do not purchase converters without a DAC chip. Do not purchase smartphones outside the well-known reputed brands such as Sony, Samsung, Motorola, Lenovo and so on.
Digital-to-Analog Conversion (DAC)
The core functionality of USB-C to 3.5mm audio converters lies in their ability to convert digital audio signals from the USB-C port into analogue signals that can be interpreted by headphones or speakers with 3.5mm jacks. This conversion process is facilitated by a digital-to-analogue converter (DAC) embedded within the converter.
The USB-C connector on the converter serves as the interface for receiving digital audio signals from the device it’s connected to, such as a smartphone or laptop. USB-C is capable of transmitting digital audio data along with power and other data streams.
Upon receiving the digital audio signal, the converter utilizes digital signal processing techniques to manipulate and prepare the audio data for conversion. This may involve tasks such as sample rate conversion, volume control, equalization, and error correction.
The processed digital audio data is then fed into the DAC, which converts the digital signal into analogue electrical signals. This analogue signal represents the audio waveform and is compatible with standard headphones or speakers equipped with 3.5mm jacks.
The analogue audio signal is output through the 3.5mm audio jack on the converter, allowing users to connect their headphones, earphones, or speakers to enjoy audio playback.
Key Components and Technologies
Several key components and technologies contribute to the functionality and performance of USB-C to 3.5mm audio converters.
Digital-to-Analog Converter (DAC): This semiconductor device is responsible for converting digital audio signals into analogue voltage signals. The quality of the DAC significantly influences the audio fidelity and overall performance of the converter.
Amplification Circuitry: Some converters may include built-in amplification circuitry to boost the analogue audio signal to a suitable level for headphones or speakers. This is particularly beneficial for driving high-impedance headphones or for enhancing overall audio output quality.
Codec Integration: Certain converters may incorporate audio codecs, such as those from Qualcomm (e.g., aptX), to support advanced audio processing features and improve wireless audio transmission quality when connected to compatible devices.
Compatibility Chips: To ensure seamless compatibility with various devices and operating systems, converters may integrate compatibility chips that handle communication protocols and signal negotiation between the converter and the connected device.
Conclusion
USB-C to 3.5mm audio converters play a crucial role in bridging the gap between modern digital audio devices and traditional analogue audio equipment. By leveraging digital-to-analogue conversion technology and integrating key components such as DACs, amplification circuitry, and compatibility chips, these converters enable users to enjoy high-quality audio playback from their favourite headphones or speakers, even when their devices lack a dedicated headphone jack.
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