Today’s review is about the Truthear Keyx, an ultra-compact USB DAC/amp designed to restore the missing 3.5mm headphone output or improve audio performance on any device with a USB type-C input.
The Truthear Keyx was kindly provided free of charge in exchange for an honest review. I didn’t receive monetary or any other kind of compensation and I don’t use affiliate links.
The price of the Truthear Keyx is $29.99 and you can buy it from Shenzhen Audio.
Truthear
Truthear is a relatively new audio brand founded in 2022, focusing mainly on making in-ear monitors and portable audio gear. The company has quickly gained attention for its tuning approach that adheres to popular target curves and their competitive prices.
Click here to read more Truthear reviews.
Truthear Keyx
The Truthear Keyx is an ultra-compact L-shaped USB DAC/amp with a 3.5mm headphone jack and an integrated USB type-C port so you don’t need to use a separate cable.
Audio decoding and amplification are assigned to a single CS43131 chip by Cirrus Logic that supports sampling rates up to 384kHz/32bit PCM and DSD256. The 3.5mm output supports earphones with a microphone for easy voice calls.
Technical Specifications
DAC Chip: Cirrus Logic CS43131
Maximum Decoding Capability: PCM384kHz/32bit | DSD256
THD+N @1kHz 0dBFS: Typ: -107dB@1Vrms 32ohm load, Typ: -112dB@2Vrms 600ohm load
Frequency Range: 20Hz – 20kHz
Plug: USB-C to 3.5mm-4Pin (SE+MIC)
DNR @1kHz-60dBFS: Typ: 122dB @1Vrms 32ohm load
Typ: 122dB @2Vrms 600ohm load
SNR @1kHz 0dBFS: Typ: 122dB @1Vrms 32ohm load
Typ: 122dB @2Vrms 600ohm load
Output Level: ≥50mW @32ohm load
Design and build quality
The Truthear Keyx features a multi-injection molded construction, combined with a CNC machined metal shell. It is ultra small and lightweight with a length that is barely 4cm and a weight that is just 4g, so it doesn’t add bulk under the phone and easily slips into a pocket.
You can use the handy integrated keyring attachment point with a spring clasp that minimizes the risk of losing it or trying to locate it in a messy backpack.
The Keyx is used in a landscape mode that reduces footprint while its USB type-C plug is cleverly elongated to fit phones with various protective cases, even thicker ones.
The EQTOOL tuning interface
The Keyx’s most unique feature is its compatibility with the EQTOOL, a web-based tuning interface that is available for PC. This powerful DSP application allows the user to customize a parametric EQ, save and share EQ profiles or load premade ones for various known earphones. The application is also used to adjust the DAC’s onboard audio parameters (like gain and low pass filter) and perform easy firmware updates.
The EQTOOL is accessible exclusively via a PC browser, but any adjustments made to the DAC’s audio settings are memorized and persist across different host devices. For instance, if you choose the NOS filter, switch the gain to high, and set the amplifier to Class AB operation, these preferences will remain in effect until they are manually changed.
Equalizer profiles, however, are not stored on the device itself. To apply and use EQ settings, an active connection to the EQTOOL is required at all times.
Output power and efficiency
The rated output power of the Truthear Keyx is 50mW@32Ω or 1Vrms in 32Ω and 2Vrms in 600Ω loads. It is best used with sensitive earphones or as a line output to an external amplifier. The noise floor is surprisingly low and the sound doesn’t get affected by the phone’s EMI.
The power consumption was measured at 60mA, one of the lowest for a USB DAC dongle with a dedicated chip, you can use the Keyx for hours and not get worried about your phone’s battery. When not in use you can leave it plugged because it will not consume any power until you connect earphones.
Listening evaluation
As long as you restrict the use with earphones that are within the Keyx’s driving limits, then the sonic performance is stellar. The use of the CS43131 DAC chip gives the Keyx an advantage over similar ultra-compact USB DAC dongles that rely on lower quality decoders, like the ddHiFi TC35B that uses the Realtek ALC5686.
The CS43131 might not run at its full potential but it still sounds neutral and transparent, just as we know it from other applications in larger USB DACs. The output power is limited but the actual sound quality of the Keyx is really good, offering an instant upgrade over any generic 3.5mm output.
Further impressions
The bass is deep enough and well defined, remaining tight and controlled without sacrificing composure or precision. Paired with the right earphones, it can also deliver a satisfyingly dynamic and punchy performance with all kinds of music.
The mid-range is tonally balanced and accurate with a convincing timbre. The textures might not be that organic or lush but they are not too lean or dry either. Instruments and voices sound realistic and expressive enough to connect the listener with the music. The Keyx doesn’t add any warmth or color to the music but it never sounds flat or sterile.
The treble is crystal clear, fast and energetic with plenty of radiating luminosity and good resolution for the category. The Keyx, just like the Shio, is smooth and polite enough, never sounding too bright or harsh. Digital artificiality and treble glare remain under control, especially if you choose to listen with the NOS filter and the Class AB amplifier mode.
Don’t expect any miracles when it comes to soundstage size or surgical imaging precision, but honestly speaking, the Keyx will not make your earphones sound congested or restrained even with large scale symphonic and choral music
Vs the competition
The Truthear Keyx is not the only ultra-compact DAC in the market, the ddHiFi TC35B and the FiiO JA11 easily spring to mind among many other options. On the other hand, larger devices, like the FiiO KA11 or the ddHiFi TC44Pro E3, don’t count as direct competitors because they are much bulkier and heavier than the Keyx.
The ddHiFi TC35B is even more compact than the Keyx but its ALC5686 decoder doesn’t sound as good, its power output is limited at 30mW@32Ω and it doesn’t connect with an EQ application.
The FiiO JA11 is also very compact but it has a different form factor than the L-shaped Keyx, it is like a short cable with USB type-C and 3.5mm plugs. The audio performance is a little inferior to that of the Keyx and its power output is limited to 30mW@32Ω. However, its biggest advantage over the Keyx is that the FiiO control application is also available for Android OS, so you can use your phone as the source when you want to apply EQ.
In the end
The Truthear Keyx is an ultra-compact USB DAC dongle with an audio performance that punches well above its modest size. The sound is so good that I would not only recommend it for adding a 3.5mm jack to smartphones that don’t have one, but also to upgrade the sonic quality of any device with a generic 3.5mm output, be it a smartphone, a tablet or a PC.
At $29.99, the Truthear Keyx is a must-have gadget that even hardcore audiophiles will fully appreciate, let alone all the rest that need a good sounding USB DAC with the least possible bulk and weight.
“A brief clarification regarding the Keyx’s drawbacks. Anyone opting for an ultra-small USB DAC dongle is typically well aware of the trade-offs that come with such a compact form factor. As a result, the absence of hardware controls or a balanced 4.4mm output shouldn’t be treated as true shortcomings, as they would be in a larger device. For this reason, I haven’t included them among the negatives.”
Copyright – 2026.
Authored by Petros Laskis for Ichos Reviews. All content is original and copyrighted. Republishing full reviews or substantial portions without written permission is prohibited. Excerpts up to 100 words are allowed with a direct link.
+ Stellar audio quality inversely proportional to its size
+ No background noise
+ Ultra-compact and lightweight
+ L-shaped form factor minimizes bulk
+ Very low power consumption
+ Fully configurable EQ and audio adjustments via the EQTOOL
+ Can fit smartphones together with their case
+ Supports earphones with microphone
+ Great value at $29.99
- The EQTOOL is web based and not compatible with Android or iOS
- Limited power output but expected from the size
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