THX Onyx Review

THX Onyx Review

23 June 2021 0 By Petros Laskis

Reign Supreme

Pros: – Reference sound
– Powerful
– Crystal clear and transparent
– Musical and engaging
– Excellent timing and dynamics
– Highly resolving
– Can drive more difficult loads
– Build quality
– Plug and play

Cons: – Increased power consumption

The THX Onyx was kindly provided by THX and doesn’t need to be returned.
THX never asked for a favorable review and as always this is my honest and subjective evaluation of it.
It is selling for $199.99 and you can buy it from here


The THX Onyx is a powerful portable digital-to-analog (DAC) amplifier equipped with THX AAA™ technology, to ensure the highest fidelity mobile listening experience for music, games, and movies.

The Onyx is the first consumer product to be manufactured by THX.

THX is now widely known for their Achromatic Audio Amplifier technology that is used by various third party manufacturers on devices ranging from headphone amplifiers to subwoofers.

The THX AAA technology ensures the ultimate no-compromise headphone audio experience by delivering the world’s highest fidelity audio with infinitesimally low levels of noise, distortion and power consumption.

Full THX AAA features are available here.

A couple of examples with products featuring the THX technology is the Drop+ THX AAA 789 linear amplifier that we have tested here and the FiiO Q3 that we have tested here.

The Onyx is quite expensive for a single ended dongle but not without a reason as we are going to find out later.


THX Onyx technical specifications

The THX AAA™ technology inside the Onyx enables the world’s highest fidelity audio and maximum dynamic range with the capacity to support power-hungry, audiophile grade headphones.

The key difference between the Onyx and similar USB dongles is that THX opted not to use the embedded headphone amplifier of the DAC chip but rather add an extra THX AAA – 78 amplifier stage.


The chip used is the top line ESS 9281PRO digital-to-analog converter (DAC) which provides best-in-class dynamic range and lowest distortion, with direct rendering of MQA files in the DAC.

The internal amplifier is disabled and the DAC analogue output is amplified by a separate THX AAA – 78 high current amplifier module.
Voltage output is a full scale 2V that translates into a whopping 180mW / 22ohm , 125mW / 32ohm and 27mW / 150ohm making the Onyx one of the most powerful single ended USB dongles in the market.
Loads lower than 22 ohm may trigger the internal protection circuit which limits current but we still get 130mW at 16 ohm.
Output impedance is as low as 0.25 ohm.


Power consumption is quite high , typically 590mW with a maximum of 900mW for extreme conditions such as full volume with low impedance load.

Crystal clean power

Another key point that sets the Onyx apart from the competition is that it uses proprietary low-noise power conversion techniques followed by a linear active filtering to transform potentially noisy 5V USB into very clean +/- 4.5Vdc power to the amplifier.
This helps ensure the noise and distortion remain very low.

THX also did the complete schematic and PCB design in-house, paying extremely careful attention to PCB layout to ensure noise and distortion from power signals doesn’t enter the audio chain.

MQA and High resolution certified

MQA Renderer technology in the THX Onyx can connect to an MQA core signal – in global streaming service apps such as TIDAL – to complete the final “unfold” of an MQA music file up to 384kHz Master.
PCM is supported up to 32bit 384kHz and DSD in DoP64 / DoP128.
All PCM and MQA files / streams are automatically up-sampled to 705.6 / 768kHz, a function that cannot be disabled.

There are three tiny LED indicators that inform the user about the sample rate.
All three LED lit blue is 44.1/48 kHz PCM , yellow is >48 kHz PCM , red is DSD and purple is MQA render.


The Onyx connects to any USB/USB-C port and works on Android, iOS, Windows 10, and Mac without the need for any drivers or installation.
A USB-C to Lightning adapter is not included but we get a female USB C to male USB A adapter.
The Onyx is compatible with mic and non-mic headphones.

Design and build quality

The Onyx is a classy and well designed device with a chassis made of CNC machined aluminium which is lightweight and tough.
A large THX logo and the three LEDs are seen on one side of the chassis.

The USB type C cable is embedded into the main body and is wrapped in a flexible and thick silicone band.
Both ends of the cable feature a heavy duty custom made strain relief that looks durable.
A built-in magnetic clasp enables quick and convenient cable management, ensuring there are no messy headphone wires dangling around.
Well we didn’t find much use of it but still nice to have as an extra option.


In order to house all the extra electronics , the Onyx is a little larger than the competition but the thin shape allows for a good handling experience.
Dimensions are 7.2x14x210mm measured with the cable.

Set up

Using the Onyx is a straightforward experience as it is plug and play with Android , Windows and Mac os.
All streaming apps are supported natively but some Android phones may need the extra USB Audio player pro application in order to get a ‘bit’ perfect high resolution playback with streaming services like Qobuz.

MQA playback

Listening to MQA on a Windows/Mac PC is easy although it requires you to take a few steps inside the Tidal app to set the output device into exclusive mode.
While writing this review Tidal has rolled out an update that supports full MQA decoding on Android with the Onyx as a DAC.
All the needed guides are available at the THX website.

The Onyx gets a little hot to the touch but not overly so to be alarming.
Extra power comes at a cost and the Onyx is going to drain your phone battery much faster than the average low powered USB dongle.


Associated gear

We have tested the Onyx with various earphones and headphones like the FiiO FH5s , Dunu EST 112 , Focal Elex and Sennheiser HD660s/650 just to name a few.
Noise floor is practically absent and below the listening threshold resulting in a crystal clear sound.


Sound impressions

Reference sound quality with top of the line transparency and a perfectly flat frequency response yet musical and engaging would be the summary for the lazy reader.

Truly Achromatic as the name would suggest the THX AAA – 78 amplifier works in perfect harmony with the 9281PRO DAC to pass the musical information without adding a character of it’s own at least in a way that it doesn’t color.

Because when seen in the grand scheme of things the Onyx does pose a character which is musical and engaging , the opposite of being called clinical , full bodied with blooming dynamics and harmonic richness.

Timbre is natural without severe digital artifacts and music sounds well textured and finely articulated.

Fast and precise with excellent timing the Onyx is able to portray the recording venue with a great sense of reality thanks to the extended and spacious stage that is well layered and proportionally aligned.

Thankfully it is not as analytical and sterile as someone would expect from a THX – ESS combination but it sounds detailed and resolving without becoming artificial and monotonous.


Bass reaches low and has a weighty and visceral feeling that remains always tight and controlled with excellent layering.
Mid frequencies , always present , shine with clarity and finesse while treble breathes energy and light in a well extended but smooth manner.
Sometimes timbre may sound just a little steely but it is not too severe to spoil the overall experience.

Compared to the EarMen Sparrow ($199)

So far so good , the Onyx is an excellent sounding DAC but not without competition.

For example the EarMen Sparrow is another excellent performer with two ES9281PRO DAC chips inside and a true balanced output while selling for a lower price.

Furthermore its balanced power output is almost the same with the Onyx while power consumption is much lower.


So why should someone opt for the Onyx?

For starters, the Onyx provides its power from a single ended output so it is out of the box widely compatible with more headphones without the need to change the cabling.

Then the extra THX AAA – 78 amplifier module makes a big difference in favor of the Onyx which outperforms the Sparrow in raw power delivery.

Listening to the same material with both devices (level matched) it is not that difficult to notice that the Onyx sounds more controlled and impactful.
Bass is fuller , faster and tighter with grander scale and far greater dynamic contrast while demanding headphones surely benefit from the extra current delivery.

The THX amplifier is able to continuously perform under extreme stress conditions and at full scale output without clipping while there is always that extra headroom when the program calls for it.

As long as we keep impedance /sensitivity in reasonable values , the Onyx can drive full size headphones with authority and without distortion reaching desktop level performance.


While the Onyx felt slightly underpowered to do justice to the HD650 with the HD660s it was a totally different experience and one of the best we have encountered from a small USB dongle.

The EarMen Sparrow can also drive the HD660S and reach loud enough but with the Onyx control always felt better and the overall presentation was more effortless especially with challenging material.

Other sonic differences will not be further discussed because both dongles share more or less the same sonic characteristics and the THX amp benefits become less important with easy loads.

At the end

The THX Onyx is a top of the line reference sounding USB dongle with power and sound reaching desktop level quality and performance.
It is more expensive than the competition but not without a reason as we have pointed out in our review.
The implementation of the extra THX AAA amplifier is a game changer and leaves the competition back by a fair margin pointing the way to the future.
If cost is no object and you want the best USB DAC dongle available then this is the one to get.

Test playlist

Copyright – Laskis Petros 2021