World Premiere! THX Onyx Review: Their First DAC/Headphone Amp Combo Is Marvelous!

THX Onyx USB DAC/Headphone Amplifier

THX Onyx USB DAC/Headphone Amplifier







What We Dig

  • Sleek Beautiful Design
  • Great Build Quality
  • Amazing Balanced Sound

What To Think About

  • Nothing at this price


The portable DAC/Amp market is a crowded one. I’ve reviewed a bunch of them, and I have a couple on deck waiting for evaluation. To make noise in this product category, you have to come up with something special.

Enter THX and their new THX Onyx, a $199 DAC/Amp that happens to be their first foray into Consumer Hardware. They came out swinging with the Onyx, a sleek device with massive power and tremendously clean sound due to their impressive THX AAA amplifier technology.

Add to that a flagship ESS DAC chip with MQA decoding, and you do, in fact, have something special here. The Onyx’s sound is stunningly transparent, with a depth and separation rarely encountered at this price point. If you’re looking for a mobile DAC/amp that provides near-reference sound at a very attractive price, you need to check it out.


● THX Achromatic Audio Amplifier (THX AAA™) for transparency and power
● Master Quality Authenticated (MQA) Renderer for Tidal Masters high-resolution audio
● ESS ES9281PRO Flagship Mobile DAC for depth and resolution
● Magnetic cable management to keep headphone wires neat and tangle-free
● PLUG and PLAY-easy connection with PC, Mac, Android, and iOS

Disclaimer: The THX Onyx was provided to us by THX in exchange for an honest, unbiased review. It doesn’t have to be returned.


I really love the design of the THX Onyx. It has a streamlined aluminum casing with the THX logo in raised relief, plus the USB cable portion is flexible and rubberized, which makes it feel quite durable.

The cable’s metallic end next to the USB connector can bend back and magnetically attach to the main body, which helps to make a compact shape for storing. You can also use the loop to hang the DAC/Amp out of the way when not in use.

It’s a nice little touch that lets you know THX had innovation in mind when creating this product. It’s really hard to believe this is their first consumer-focused piece of hardware.

You see, THX is known more for licensing audio technology and standards to other companies that build and market the hardware than building their own.

For example, THX Achromatic Audio Amplifier (THX AAA™) circuitry, which forms the heart of THX Onyx, has started a craze via products like the THX AAA ONE and THX AAA™ 789 desktop headphone amps from Drop.

On the portable side, HELM Audio utilized a mobile variant of the THX AAA amp in their DB12 AAAMP Headphone Amp, which provided tons of power and transparency when we tried it last year.

That product used the THX AAA-38 mobile amp circuit, but THX included its best mobile amp circuit in the Onyx, namely the THX AAA-78. The AAA-78 offers about double the power output of the AAA-38, and at 180mw into 22 ohms, the Onyx has output power that rivals many desktop amps.

That means it will drive some of the most power-hungry cans on the market with no problem, including my Dan Clark Audio Aeon Flow Closed headphones, which are known for being hard to drive properly. Even with the AFC headphones, I never had to raise the volume level above 50%, and I heard none of the compressed dynamics I have heard with other portable amps.

The “Achromatic” in Achromatic Audio Amplifier means “without color.” That speaks to the amp circuit’s promised lack of distortion or noise, which THX says provides a “realistic, fatigue-free” listening experience. Most who have listened to it, including me, agree.

To achieve this, THX AAA uses a patented version of feed-forward error correction which means two inverted signals are summed at the output canceling out distortion and removing noise. This is the same principle used in high-end THX AAA desktop amps like the Benchmark HPA4 headphone amplifier.

This transparent amp section is combined with a high-quality DAC section based around the ESS ES9281PRO DAC chip. It offers very low total harmonic distortion, MQA rendering, and PCM decoding up to 32-bit 384kHz PCM. The THX Onyx also handles DSD128 over PCM.

Of course, as an MQA renderer, it needs a software decoder like the Tidal Desktop App to do the first unfold of an MQA file, then it will take the 24-bit signal and do the final unfold to a higher bitrate if encoded in the file. The Onyx also 8x up-samples the signal within the DAC to 705.6/768 kHz before the D to A conversion.

On the top of the amp are three led lights that different colors to indicate what signal is going through the DAC. For example, 3 magenta lights mean MQA is being decoded, while 3 yellow lights mean a PCM signal above 48 kHz is being processed. Red indicates a DSD signal. The lights are bright and easy to read.

The THX Onyx has a permanently attached USB-C connector to plug into most newer smartphones and laptops, but if you have a laptop that doesn’t have USB-C, you can use the included USB-A adapter to connect. Apple folks with iOS devices will need the Apple Lightning to USB Camera Adapter (slim version) to plug into that stuff.

By the way, if you are a gamer, the THX Onyx supports mic input from a headset as long as it uses a 3.5mm TRRS plug, which is quite common. This will let you upgrade the audio for games as well as music. That’s pretty cool.

Listening to the THX Onyx Portable DAC/Amplifier

To test out this DAC/Amp, I connected it to both a Moto G Fast smartphone and my HP Envy Laptop via USB-C. On the Smartphone, I played a bunch of MQA tracks from Tidal through the USB Audio Player Pro app. I also used the Desktop version of the Tidal App, playing the same music from the Audiophile 101 MQA playlist on the Laptop.

As far as headphones are concerned, I mainly used the Focal Elear, and The Mr. Speakers (now Dan Clark Audio) Aeon Flow Closed planar magnetic headphones. I also tried the Hifiman Sundara planar magnetic headphone and the Periodic Audio Carbon earphone to see how it did with IEMs.

I noticed right away about the THX Onyx how extraordinarily crisp and balanced this Dac/AMP is. It is extremely transparent and flat. That means it really allows the headphones to shine and do their thing. As such, it sounded good with every pair of headphones I threw at it.

I wouldn’t worry about matching too much with the Onyx; just find a pair of headphones you like and plug them in. You should be delighted with the result.

Also, as I said earlier, this DAC/Amp combo should be able to power just about any headphone out there, including power-hungry Planar models with no sweat. I really enjoyed the Onyx with the Aeon Flow Closed, a pair of headphones that really need some juice to open up, and the THX amp did so at less than 25% of volume.

Listening to Angus and Julia Stones’ “Draw Your Swords,” I was amazed at how the Onyx allowed the AFC to present micro-dynamics, such as the guitar strings’ trailing notes and the echo of the male vocal in the recording space. It was out of this world. As far as macro-dynamics were concerned, it also did a good job reproducing the punch of the kick drum and the presence of the guitar strumming.

On the song “Babylon Sisters” by Steely Dan, the Onyx played the song with nice depth and punch through the Focal Elear; it also played all the vocal parts with crispness and separation. It’s crazy how transparent this amp is. It’s hard to believe you’re listening to a USB DAC; it really has performance more on par with a desktop unit.


I compared the THX Onyx with two other USB Dac/Amps with MQA, the Audioquest Dragonfly Cobalt ($299), and the Helm Audio Bolt DAC, which is THX Certified ($99).

The BOLT was clearly a step down from the Onyx in both power and transparency. While it sounds amazing for its price, giving you nice timbre on instruments and vocals, plus decent detail, the Onyx was just more open and had more depth, giving you more sense of the recording space and just more detail overall.

The comparison with the Cobalt was much closer. Powerwise, even though the Onyx has more power output on paper, it didn’t really matter because both amps will play just about any pair of headphones louder than you have any business playing them.

As far as sound quality is concerned, I would say the Cobalt has more detail and separation overall, but I would say the difference is very slight. That’s significant because the Cobalt is $100 more at retail, and I can’t say the Audioquest DAC sounds anywhere near $100 better.

The Cobalt gives you more spatial cues, and transients are a little more fleshed out. It also sounds more layered than the Onyx. However, I would say the Onyx’s overall tonal balance is better as the Cobalt can sound a little hard on certain tracks, something the THX product has no issue with.

At the end of the day, I would say the Onyx gives you about 90% of the detail, separation, and layering of the Cobalt, so if you don’t have $300 to spend, just don’t want to spend that much, or you want something easier to carry, the THX Dac/Amp is a darn good choice.

The Wrap Up

At $199, The THX Onyx may be the best value in USB DAC/Amps today. It has crazy power, a clean, transparent sound that is breathtaking, and a sleek design that makes it easy to carry around. The well-thought-out mix of features also makes it quite flexible for many different use cases.

Music lovers who are looking for a lightweight USB Dac/Amp that compete with Desktop models for both output power and sound quality, then you should give the THX Onyx a look.


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