USB Audio Device Class 3.0: A New Standard

Welcome to what I call the second Wednesday of this week, or as you might know it, Thursday. Today, I’m delving into USB Audio Device Class 3.0.

USB 2.0 has always been a good fit for audio. Even the highest quality audio streams, with seven channels of audio at the highest bit rates, fit comfortably into the bandwidth that USB 2.0 offers. However, there was always the issue of power consumption with the existing USB audio standard. USB headsets, while popular among PC gamers, haven't seen the same level of adoption for mobile phones. Mobile phone users have traditionally preferred 2.5mm analog headphones.

USB audio, in its current form, is so efficient that USB 2.0 can easily transmit super high-quality audio. Yet, consumers have shown a strong preference for their analog headphones – those affordable, colorful ones with the 2.5mm connector. But here’s the rub: phone makers are flattening their phones and removing the 2.5mm headphone connector. They expect consumers to switch to Bluetooth wireless headsets, which, despite being available for under $15, haven't dampened the popularity of 2.5mm headphones.

Enter the new Audio Device Class 3.0, introduced by phone makers and the USB-IF. This standard focuses on power savings by reducing the time the audio and USB circuitry are active. By maximizing off time, it conserves power, sending data in bursts from the source (like a phone) to the USB headphones.

Old 3.5mm analog headphones, designed over a century ago for telephone switchboards, were always on, consuming power continuously when transmitting audio. This constant power transmission is gone with today’s phones, as the 2.5mm jack is too bulky and possibly challenging to waterproof.

USB headphones have typically used the Standard A connector for PCs, meaning they weren’t designed for phones or tablets. The audio quality is potentially higher than analog since the digital signal is transmitted through USB and unpacked near your ear. However, this USB audio is always on, consuming power continuously. Thankfully, both Microsoft and Apple provide standard drivers, making USB audio headphones easy to use. In fact, for their reasonable pricing and sound quality, I personally prefer Microsoft headphones for music or conference calls.

To address power consumption on mobile devices, the USB-IF created the Audio Device Class 3.0 (ADC 3.0). The primary benefit of this standard is that audio transmits in bursts, significantly reducing power usage. The USB components are only active about 10% of the time, potentially reducing power consumption by 90% or more. As mobile phone makers strive to extend battery life, a 90% reduction in any area is a substantial gain.

ADC 3.0 technology promises not only higher audio quality but also compatibility with modern mobile phones thanks to its Type-C connection. Moreover, ADC 3.0 headphones can offer even greater power savings and customized features when used with phones from the same manufacturer.

The future of ADC 3.0 headphones is bright. They are poised to be cost-competitive with low-energy Bluetooth headphones and offer better battery life. It’s only a matter of time before we see USB ADC headphones at very affordable prices, although they might be slightly more expensive for now.

For more on what Synopsys has done for USB Audio, feel free to get in touch with us. And for a bit of humor, enjoy these two XKCD comics that perfectly capture the quirks of USB technology.