What Class is my USB Audio?

There are dozens of nice digital to analogue converters which you can use to improve your computer’s sound quality. But they are divided into two classes. Which should you choose?

USB Audio Classes

Everything to do with USB is governed by standards and protocols. That’s why it all works so well. Plug a gadget into the USB port on your computer, and both the gadget and the computer know what they’re supposed to do to communicate with each other. The same is true for USB Audio devices.

At a pinch, you can plug headphones into your computer and listen to streaming music. But computers are certainly not optimised for high quality sound. Far better is to plug an external digital to analogue converter – DAC – into one of the computer’s USB ports. When you plug your headphones into that you're going to get much better sound. But one choice you need to make in choosing a DAC is whether it conforms to USB Audio Class 1.0 or USB Audio Class 2.0 standards.

AudioQuest DragonFly Red

AudioQuest DragonFly Red DAC – highly compatible thanks to USB Audio Class 1.0 compliance

Well, surely 2.0 is better than 1.0, right? Well, it depends.

USB Audio Class 1.0 vs USB Audio Class 2.0

USB Audio Class 1.0 supports PCM (Pulse Code Modulation) digital audio standards up to 24 bits resolution and 96kHz sampling. That is, it supports genuinely high-resolution audio. That was good enough for many years, but higher and higher resolution audio is becoming increasingly available, along with alternative formats such as Direct Stream Digital.

USB Audio Class 2.0 goes well beyond that and seems to be able to handle any audio standard that can fit within the 480Mbps data transfer limits of USB. I have personally tested DACs – such as the Topping E30 pictured at the top – with PCM audio with 32 bits of resolution and 384kHz sampling (almost 25Mbps, not counting encoding overhead) and DSD512 (more than 45Mbps). If the DAC supports them, they’ll work. I have no doubt that if I ever manage to get my hands on a 768kHz PCM track – I’m working on it – it also will work, despite requiring a bitrate of close to 50Mbps.

So, USB Audio Class 2.0 is better, right?

Again, it depends. What computer are you using and what operating system is it running? If it’s a Mac, then all other things being equal, go for USB Audio Class 2.0. If it’s a recent Windows computer and your Windows 10 installation is up-to-date, then, again, go for USB Audio Class 2.0.

But if you’re still running Windows XP, Windows 7, Windows 8 or an early version of Windows 10, things are more complicated. Those versions of Windows did not natively support USB Audio Class 2.0. So to use such a DAC you have to install special drivers from the hardware manufacturer.

That changed with the Windows 10 Creators Update, Version 1703, in 2017. That finally, belatedly, added USB Audio Class 2.0 support to Windows. My early experiences with it weren’t very good, but within a year or so further updates got Windows working well natively with Class 2.0 DACs.

I do recommend using manufacturer’s drivers for some DACs if they’re available. DACs are starting to appear with support for PCM with 768kHz sampling and for DSD512. The WASAPI interface built into Windows tops out at 384kHz and 32-bit support. You’ll need ASIO (Audio Session Input/Output) drivers for those higher rates. In addition, the occasional DAC is not “Class Compliant”, which means it must use its own proprietary drivers.

Which DACs are which?

It’s not always clear whether a DAC supports USB Audio Class 1.0 or 2.0. But you can usually tell just by the specifications. If the specs say a DAC is good for up to 24 bits and 96kHz, it’s almost certainly USB Audio Class 1.0 compliant. If they say it can handle 192kHz or higher, or that it can decode Direct Stream Digital (DSD), then it’s definitely USB Audio Class 2.0.

Cambridge Audio DacMAGIC 100

Switchable USB Audio Class 1.0 and 2.0

One DAC that I used for several years, the Cambridge Audio DACMagic 100, works in both modes. Out of the box it is in Class 1.0 mode, but if you want to use its 192kHz capabilities, you can switch it to Class 2.0.

Don’t automatically dismiss USB Audio Class 1.0. The ultra-portable AudioQuest DragonFly range of DACs are well regarded and offer rare support for MQA (Master Quality Authenticated) audio, yet are pure Class 1.0 devices.

But if you want to handle all high resolution digital files, you’ll really want a USB Class 2.0 DAC.

AudioquestCambridge audioDacsTopping