Many people these days use wireless headphones and headsets, but there’s definitely a limit to the quality of audio they can stream. This explains why most audiophile-level headphones are still wired, and why there is still a (small) market for headphone amps, which can improve the quality of your audio even further. The first USB headphone amp from THX, the Onyx, packs an impressive amount of power and Master Quality Authenticated (MQA) decoding into a tiny $199 package. We’re currently waiting for Tidal to update its Android app to support the Onyx with MQA decoding before we give it a full review, but we have some initial thoughts based on testing it with a PC.
Tiny But Mighty
The black, rectangular Onyx is smaller than a stick of gum, measuring just 2.4 by 0.5 by 0.3 inches (HWD). It features a silver THX logo and three multicolor status lights that glow depending on the bit rate of the audio being processed. There are no physical controls.
A 5.5-inch cable extends from one end, terminating in a USB-C plug (an included adapter converts it to USB-A if you don’t have a USB-C port). The back of the amplifier has a magnetic spot near the bottom that holds the USB plug in place, so you can keep the cable nice and tidy when it’s not in use. The plug is a bit too thin to keep the amplifier folded over when it’s attached to a phone (unless the phone is also very slim).
Inside the tiny rectangular box sits an ESS ES9281PRO digital-to-analog converter (DAC), a THX Achromatic Audio Amplifier AAA-78 amp chip, and a Master Quality Authenticated (MQA) renderer that can process digital master recordings. It has a dynamic range of 118db and an output power of 180mW per channel with 0.2-ohm impedance.
The Onyx works with any Mac or PC with a USB-A or USB-C port, and is compatible with both Android and iOS devices (though iPhone users will need Apple’s $29 Lightning-to-USB adapter). The 3.5mm headphone jack is compatible with both three-pole headphone connectors and four-pole headset connectors, and supports microphone input to the connected device.
The three LEDs on the Onyx display the amp’s status and the sampling rate of any audio playing through it. They glow blue with 44.1 or 48kHz PCM audio, yellow with PCM audio greater than 48kHz, red with Direct Stream Digital (DSD) audio, and magenta with any Master Quality Authenticated (MQA) content. Of these different audio types, MQA is the highest quality.
(Sort of) Plug and Play
No matter what you connect it to, the Onyx is ostensibly a plug-and-play device. It was detected automatically by both my PC and Samsung Galaxy Note 20 when I plugged it in, and provided audio output with both. However, getting higher-quality audio is a bit more complicated than that.
When I plugged the Onyx into my PC and listened to music through Tidal set to Master quality, I only got yellow lights, indicating high-quality PCM audio rather than the MQA audio I expected. When I plugged it into my phone, I got blue lights indicating standard PCM audio.
Thankfully, enabling MQA decoding on my PC was relatively easy through the Tidal app. I clicked on the output devices icon in the lower right corner of the app, then clicked on More Settings next to the Onyx. After I set Exclusive Mode to on, the Onyx showed magenta lights when I played master tracks.
Tidal is updating its MQA decoder on Android to support the Onyx, but it wasn’t ready at the time of this writing. We’ll update this story with our experience when the decoder is released, so we can properly test the device on Android and compare its performance with a standard USB-C-to-headphone adapter.
Like New Ears
You probably keep the volume levels on your phone and PC fairly high, especially if listening through a headphone jack—don’t do this with the Onyx. Built-in headphone jacks usually output fairly low power, while the Onyx can pump out 180 watts. When I first tested it, I had my volume set high, and as soon as I started playing music, I nearly threw my headphones across the room. Start at around 25% on your device and see how your headphones sound through the Onyx, then adjust accordingly.
I tested the amp on my Windows 10 laptop by playing Master tracks on Tidal, listening through a pair of Turtle Beach Elite Pro 2 headphones. I switched between the laptop’s headphone jack and the Onyx for each track and compared them. First, the aforementioned difference in volume is astounding. A volume level of 30% on the Onyx is equivalent to the laptop’s headphone jack at maximum volume, and pumping the Onyx above 30% eventually gets loud enough to become physically painful.
I listened to Fleetwood Mac’s “Tusk” (2015 remaster) and was taken aback by the improvement in sound quality when using the amp. The track certainly doesn’t sound bad through the laptop’s headphone jack, but the MQA-decoded, amplified output of the Onyx is a real cut above in detail. From the start of the song, I could hear the marching band milling around in the background and pick out individual instruments. When the drums started, they sounded realistic and full, with much more detail in the attack of each hit. Lindsey Buckingham’s vocals were lifelike, and I could even make out his breaths in between lines. All of these details sounded muted or outright muddled through the standard headphone jack.
The much more synth-heavy “Aerodynamic” by Daft Punk doesn’t have nearly as much detail or texture to bring out, but the Onyx still offers a better listening experience with palpably better dynamic range. A few bars after the riff of the song kicks in, the bass of the backing drums gets noticeably pumped up, adding significant thump to the track. I barely noticed that boost in bass through the standard headphone jack, but I could really feel it through the Onyx.
The White Stripes’ “Blue Orchid” also gets a nice boost in dynamic range and detail through the amp. Jack White’s vocals sound a bit more real, but the biggest change I noticed was in the drums. The kick drum hits get a slight echo I never heard before, and the trailing of the cymbals comes through so much more clearly, making each crash flow into each other instead of simply keeping up with the beat.
Waiting on Android
A headphone amp can bring much more detail and power to your listening experience, and the THX Onyx looks to be an excellent new option. The difference in clarity and range between a standard headphone jack and the Onyx is frankly shocking, but we’re holding off on scoring the amp until Tidal updates its Android app to support MQA with USB devices and we can test it. Check back for a full review and rating once it does.
