The USB Implementers Forum this week published the USB Audio Device Class 3.0 specification, which standardizes audio over USB Type-C interface. The new spec enables hardware makers to eliminate traditional 3.5mm mini-jacks from their devices and use USB-C ports to connect headsets and other audio equipment. Makers of peripherals can also build their audio solutions, which use USB-C instead of traditional analog connectors. Developers of the standard hope that elimination of mini-jacks will help to make devices slimmer, smarter and less power hungry.
The industry, led by Intel and some other companies, has been mulling about replacing the traditional 3.5mm mini-jack connector for some time now. The main motives for replacement were necessity to simplify internal architecture of devices by removing analog and some audio processing components from the inside (which leads to further miniaturization), minimize the number of external connectors, improve power management as well as to add smart features to headsets and other audio equipment. We discussed USB Type-C Audio Technology briefly earlier this year and mentioned that this isnot the first time that the industry has tried to use USB instead of the good-old mini-jack. The important difference between contemporary initiative and attempts in the past is the fact that today the primary goal is to replace the 3.5mm jack in portable devices.
As reported, the USB Audio Device Class 3.0 specification supports both analog and digital audio. Analog audio is easy to implement and it does not impact data transfers and other functionality of USB-C cables since it uses the two secondary bus (SBU) pins. Some device makers may find analog audio feature of the standard as a relatively simple way to add certain smart capabilities to their headsets without major redesign of hosts. While analog USB-C audio will not help to shrink dimensions of portables, it could be particularly useful for non-mobile devices, where miniaturization is not crucial, but where port space is at a premium or where additional features either make sense (infotainment, sport equipment, etc.) or are fundamental (VR HMDs).
The USB ADC 3.0 defines minimum interoperability across analog and digital devices in order to avoid confusion of end-users because of incompatibility. In fact, all ADC 3.0-compliant hosts should support the so-called headset adapter devices, which allow to connect analog headsets to USB-C. However, digital audio is one of the primary reasons why companies like Intel wanted to develop the USB-C audio tech on the first place, hence, expect them to promote it.
According to the USB ADC 3.0 standard, digital USB-C headphones will feature special multi-function processing units (MPUs), which will, to a large degree, define the feature set and quality of headsets. The MPUs will handle host and sink synchronization (this is a key challenge for digital USB audio), digital-to-analog conversion, low-latency active noise cancellation, acoustic echo canceling, equalization, microphone automatic gain control, volume control and others. Such chips will also contain programmable amplifiers and pre-amplifiers, which are currently located inside devices. Besides, USB ADC 3.0-compatible MPUs will also support USB Audio Type-III and Type-IV formats (the latest compressed formats), but will retain compatibility with formats supported by ADC 1.0 and 2.0. Finally, among the mandated things set to be supported by USB-C Audio devices are new Power Domains (allows devices to put certain domains in sleep mode when not in use) as well as BADD (basic audio device definition) 3.0 features for saving power and simplified discovery and management of various audio equipment (each type of devices has its own BADD profile).