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Headphone amp/DACs: The best way to enjoy lossless audio

Now that pretty much every major streaming music serviceexcept Spotify — offers lossless audio options at CD-quality or better, you may be wondering how you can hear that extra level of sound quality for yourself. The bad news is that, no matter how awesome your wireless headphones or true wireless earbuds may be, lossless audio and Bluetooth remain fundamentally incompatible.

The only way to hear true lossless audio from your phone is via a wired connection. And if your phone lacks a headphone jack — as most do these days — how do you get around this obstacle? The answer: A dongle-sized portable headphone amp/DAC (digital-to-analog converter). These tiny devices may not look like much, but they’re packed with technology and offer a better audio experience than you might get with a simple $15 headphone dongle from your favorite online retailer.

A collection of five portable headphone amp/DACs.
Simon Cohen / Digital Trends

Here are five headphone amp/DAC dongles we think are worth a look at. We tested each one using a set of Sennheiser HD 560S open-back headphones, with a Google Pixel 5, and, when possible, an iPhone 11. As a music source, we listened to Apple Music, Tidal, and Amazon Music, with a mix of lossless tracks — some at CD-quality (16-bit/44.1kHz) and some at hi-res quality (24-bit/48kHz/96kHz/192kHz). We also listened to MQA tracks from Tidal on all of the devices except the A&K USB-C Dual DAC. No DSD tracks were used for this comparison.

All five devices performed very well, delivering audio quality that was noticeably better than we could achieve with a simple adapter like Apple’s $8 Lightning-to-3.5mm dongle, which we used as a baseline. However, there were some differences between each model.

THX Onyx, $200

The power player

  • iOS, MacOS, PC, and Android
  • Headphone mic compatible: Yes (except iPhone)
  • Maximum output power: 2Vrms
  • PCM: Up to 32-bit/384kHz
  • DSD: Up to 5.6Mhz
  • MQA compatible: Yes

As the most expensive headphone amp/DAC we tried, the THX Onyx has a lot to live up to. It mostly succeeds, especially when it comes to power, thanks to its Achromatic Audio Amplifier (AAA), which can output up to 350 milliwatts when paired with a set of 32 ohms headphones. By contrast, the Questyle M12 outputs 26.71 milliwatts at 32 ohms. The Sennheiser HD 560S have a higher impedance (120 ohms) than most headphones, and thus they require more power to drive them correctly, but the Onyx had no problem at all.

I found that the Onyx was particularly good at rendering MQA files, offering a slightly smoother overall sound than some of the other MQA-capable DACs. It was also a solid performer for all kinds of music, providing an excellent tonal balance while enhancing the already wide soundstage of the Sennheiser HD 560S.

Like most DACs, the Onyx has a set of three LEDs on its slender metal body that give you a visual confirmation of the stream you’re playing: Purple for MQA, red for DSD, gold for hi-res audio over 48kHz, and red for audio with a sampling frequency of either 44.1 or 48kHz.

At 8 inches, the THX Onyx has the longest dimensions of the five models we looked at and it also has the largest body. It can be a bit bulky to deal with when on the road with your phone — something that only gets trickier if you need to use an adapter for the iPhone’s Lightning port. When not in use, the soft and very flexible cable can fold in half, and magnets embedded into both the USB-C end and the body keep it from flopping about when not in use. It comes with its own USB-A adapter, but you’ll need to buy a Lightning adapter for use with an iPhone or other Lightning devices.

Helm Bolt USB DAC, $99

No nonsense DAC

Helm Bolt USB DAC.
Simon Cohen / Digital Trends
  • iOS, MacOS, Windows, and Android
  • Headphone mic compatible: Yes (except iPhone)
  • Maximum output power: 2Vrms
  • PCM: Up to 32-bit/384kHz
  • DSD: Up to 5.6Mhz
  • MQA compatible: Yes

The Helm Bolt USB DAC is the bulldog of the group, with a very small body that is extremely robust. Between its braided nylon cable, which is flexible but strong, and tough plastic shells used for both connector ends, I’m confident the Bolt will survive a lot of abuse. It’s also very light, which keeps it from exerting any strain on your phone’s port or your headphone’s cable. Plus, of the five devices we tried, the Bolt’s headphone jack felt like it had the tightest fit, with a very positive click when you insert a 3.5mm plug. The Bolt comes with its own USB-A adapter, but you’ll need to buy a Lightning adapter to use the DAC with an iOS device.

A small LED indicator gives you a visual confirmation of the source signal — blue: Sample frequency of 48kHz or less, red: Sample frequency greater than 48kHz (hi-res audio), and magenta (purple) when playing MQA streams.

In terms of sound quality, the Bolt offered very similar performance to the other devices on this list, with plenty of volume and almost no discernible distortion.

Questyle M12 Portable Headphone Amp and DAC, $140

Maximum versatility

Questyle M12.
The Questyle M12 Portable Headphone Amp and DAC seen with an optional Lightning adapter cable. Simon Cohen / Digital Trends
  • iOS, MacOS, Windows, and Android
  • Headphone mic compatible: Yes (except iPhone)
  • Maximum output power: 2Vrms
  • PCM: Up to 32-bit/384kHz
  • DSD: Up to 11.2Mhz
  • MQA compatible: Yes

The Questyle M12 is the only DAC we tried that doesn’t have a built-in cable. This has two advantages. First, it means that if a cable or connector happens to break, you can simply buy a new one instead of replacing the entire unit. Second, it lets you choose the specific connector type for your device — whether that’s USB-C, USB-A, or Lighting, without having to daisy-chain two sets of plugs. This is definitely something to consider if you plan to use the DAC with more than one device on a regular basis. The all-metal body is very well built and only adds a bit of weight to the end of the cable. The M12 comes with two cables in the box: A USB-C to USB-C and a USB-C to USB-A, giving you the option of mobile or computer use. You can also buy a separate USB-C to Lightning adapter (pictured above) to give you iOS compatibility.

Questyle has included two kinds of LED indicators. A gain indicator shows whether the amp is set to low (green) or high (red) gain — this can’t be adjusted as the gain level is automatic — a nice reminder that the amp knows the needs of your chosen headphones. While testing with the Sennheisers, that light was always red. Switching to a lower impedance set of headphones like the Sony WH-1000XM4, turned the light green.

The second indicator is for stream identification, but unlike some of the other DACs here, the M12’s display discerns only between distinct stream types (MQA, DSD, or PCM), and not the sampling frequency of the PCM signal. Green: PCM, red: DSD, and magenta (purple) for MQA. The M12 does a superb job of powering different kinds of headphones and sound quality was excellent from both my iPhone and Google Pixel. There was only one problem I encountered: When I plugged the M12 into my Mac using the USB-A adapter and listened via the Sennheisers, the DAC generated an audible popping sound. This didn’t happen when I used lower impedance cans, so my guess is it has to do with the higher gain the M12 uses when connected to the Sennheisers. I’ve reached out to Questyle for its take on the situation and will update this post if/when I hear back.

Astell&Kern USB-C Dual DAC Cable, $149

The sound of metal

Astell&Kern USB C Dual DAC Cable.
Simon Cohen / Digital Trends
  • MacOS, Windows, and Android (no iOS support)
  • Headphone mic compatible: No
  • Maximum output power: 2Vrms
  • PCM: Up to 32-bit/384kHz
  • DSD: Up to 11.2Mhz
  • MQA compatible: No

In some ways, the Astell&Kern USB-C Dual DAC Cable is the least capable device in this roundup. It doesn’t work with Lightning-based iOS devices at all (even with an adapter), it doesn’t support microphone use (though audio is still fine if your headphone cable has an inline mic), and it does not support MQA rendering. That makes it hard to justify its $149 price. But the all-metal construction of the Dual DAC Cable is undeniably cool, as is its A&K’s signature polygon styling.

The four-wire twisted cable looks a little fragile, but A&K claims that it can withstand a lot of abuse. That’s a good thing because, at 0.9 ounces, the Dual DAC is the heaviest of the DACs on the list — the next runner-up is the THX Onyx at 0.6 ounces. With that much weight, there’s a fair amount of stress on the cable and the plug. I also noticed that when inserting a 3.5mm headphone plug, the A&K doesn’t give you a click-fit. Instead, the jack relies on pressure from the internal connectors to keep the plug seated. That works well enough when you’re not moving, but it doesn’t take much force to pull the plug free from the jack.

Unlike the other DACs, the Dual DAC doesn’t give you any kind of visual feedback in terms of its LED — which is either on or off. There’s no way to be sure if the dongle is receiving a lossy signal or a hi-res file at 24-bit/192kHz.

Despite these shortcomings, the Dual DAC is the only DAC on our list that does not use DAC chips from ESS. Instead, it uses two Cirrus Logic DACs in parallel — one DAC performing the left channel conversion, while the second manages the right channel. For purists, this arrangement is like catnip, offering better precision, balance, and cleaner amplification. There’s no doubt about it — the Dual DAC sounds great, with impressive precision through midranges and high frequencies alike, with fast and punchy bass response. Once again, there was no problem when using it to power the more demanding Sennheisers and other headphones were equally well-served by the Dual DAC.

Zorloo Ztella MQA Version, $99

Tiny but mighty

Zorloo Ztella MQA version.
Simon Cohen / Digital Trends
  • iOS, MacOS, PC, and Android
  • Headphone mic compatible: Yes (except iPhone)
  • Maximum output power: 2Vrms
  • PCM: Up to 32-bit/384kHz
  • DSD: Up to 5.6Mhz
  • MQA compatible: Yes

I’ve got no idea how Zorloo managed to squeeze DAC and amplification into the tiny Ztella, but somehow this little shrimp of a cable possesses many of the same characteristics as the far bulkier models on this list. At just over 0.1 ounces, you may as well say it weighs nothing at all. For that reason alone, it’s worth your consideration. We tested the MQA version, but if you don’t need this feature, Zorloo also makes a non-MQA version that costs less but is in every other way identical. It ships with a USB-A adapter, but you can also buy it as a bundle from the Zorloo website with a Lightning adapter for a few dollars more.

The LED indicator is embedded in the USB-C connector where it’s easy to see as long as it’s facing up, and it uses a similar color pattern as the other DACs: Blue for idle or PCM audio that has a sampling frequency of 48kHz or less, red for sampling frequencies of greater than 48kHz, and magenta (purple) for MQA content.

My only critique of the Ztella is that it might not be as well built as the other devices on this list. After a few weeks of use, the metal collar on the headphone jack came loose, and I had to start twisting the headphone plug within the barrel of the jack in order to keep sound going to both left and right speakers.

But when the stars (and electrical contacts) align, the Ztella punches well above its diminutive size, with tons of power and very good sound quality.

Research and buying tips

What’s the difference between a DAC, an amp, and a headphone adapter?

A DAC performs the conversion of a digital audio signal (which is basically just ones and zeroes) into an analog signal that you can hear through headphones or speakers. All audio that comes out of a device like a smartphone, tablet, or computer must go through a DAC before you can hear it. DACs can vary in their capabilities and the quality of their conversions, which makes the DAC a key component in the sound you hear when playing digital audio.

An amplifier (amp) takes an analog audio signal and boosts its power to match the needs of your headphones or speakers. If an amp is too weak for your chosen gear, the volume will be lower than you expect and the sound that you do hear won’t be especially high quality. Many audio enthusiasts take great care to use an amp that can provide a strong and accurate signal to their headphones or speakers.

Headphone adapters for phones that don’t have their own headphone jack use a DAC to convert the digital audio signal from a phone’s USB-C, Lightning, or another kind of port, into an analog signal that is made available through the adapter’s headphone jack. Generally speaking, these adapters don’t provide much in the way of amplification, making them a poor choice for some headphones, and their DAC might be limited to specific digital bit depths and frequencies. This prevents them from offering the full quality of some digital audio files.

Why should I buy a portable headphone amp/DAC instead of a headphone adapter?

Portable headphone amp/DACs are designed to offer both high-quality and versatile digital-to-analog conversion as well as multiple levels of gain (amplification) to accommodate the power requirements of a wide variety of headphones. While these devices may not offer a noticeable difference when using an inexpensive set of wired earbuds, those with high-quality headphones or in-ear monitors (IEMs) should notice a considerable improvement in sound quality.

Can I use a portable headphone amp/DAC on my computer?

Yes. If your computer has USB-C ports, you can probably plug the headphone amp/DAC in and use it right away. Most portable headphone amps/DAC also come with a small adapter that lets them be plugged into a standard USB-A port too.

Do portable headphone amp/DAC need to be plugged into a power source?

Dongle-style portable headphone amp/DACs are designed to pull power from their host device (a phone, tablet, or computer) and they don’t need a separate source of power. However, other kinds of portable headphone amp/DAC, which tend to be larger in size, need to be plugged into a power source, or they may have internal rechargeable batteries that need to be occasionally recharged before they can be used.

Do all portable headphone amp/DACs work on all phones and computers?

No. Some of these devices are only compatible with specific types of phones or computers. For instance, the Astell&Kern USB-C Dual DAC Cable listed above is not compatible with Lightning-port products like iPhones and older iPads (even if you use a Lightning-to-USB-C adapter), but it does work with USB-C and USB-A-equipped Macs and iPads. Definitely check the compatibility of a portable headphone amp/DAC before buying it to make sure it works with your products.

Can I still use my headphones’ microphone if I use a portable headphone amp/DAC?

It depends. Most portable headphone amp/DACs support this feature when connected directly to a phone or computer without using an adapter. However, this feature can stop working when an adapter is used, e.g. a USB-C-to-Lightning adapter for iPhones. Again, check the specs of the portable headphone amp/DAC to be sure it will support your needs.

Will a portable headphone amp/DAC let me play every kind of digital audio?

The software on your phone or computer is responsible for converting a wide variety of compressed digital formats like MP3, AAC, ALAC, FLAC, Ogg Vorbis, etc., into pulse-code modulation (PCM) — an uncompressed digital signal that is understood and processed by all DACs. PCM signals can have a bit-depth of up to 64-bit, and a sampling frequency of up to 384kHz, though the majority of digital music uses a maximum of 24-bit/192kHz, which is considered hi-res audio. All of the portable headphone amp/DACs we tested above are compatible with all of these PCM bit-depths and frequencies. In other words, these devices will work for the vast majority of the digital music you will likely encounter.

However, there are two kinds of digital audio that do not get converted into PCM before arriving at the DAC: DSD and MQA. A portable headphone amp/DAC must specifically support these formats in order to play them.

DSD (direct stream digital) is a high-resolution format that uses a 1-bit depth but comes in as many as five sampling frequencies, from 2.8 MHz to 45.2 MHz. You won’t find DSD on any streaming service, but music lovers continue to acquire DSD audio files as downloads and by ripping tracks from SACDs and DVD-audio discs. All of the portable headphone amp/DACs we tried support DSD at 2.8 and 5.6MHz, but only the Questyle M12 and A&K USB-C Dual DAC support DSD at up to 11.2MHz.

MQA is a proprietary digital audio format that can deliver both CD-quality and hi-res audio as a single file. Any music playback app that supports MQA will let you hear the CD-quality level, but to get the full hi-res level of quality, you need a DAC that supports MQA rendering. Of the portable headphone amp/DACs we tested, only the A&K USB-C Dual DAC doesn’t support MQA. You can access the MQA format via Nugs.net and Tidal HiFi, which uses the format for its Master audio tracks, but it’s also available as a download or on physical media.

Always check the specs to make sure the formats that matter to you are included.

Does it make sense to buy a portable headphone amp/DAC if I’m just listening to lossy digital audio like MP3s or streaming from Spotify?

Yes, but the primary benefit will be the improvement of amplification. Portable headphone amp/DACs can deliver a cleaner, more powerful signal to your headphones and that will improve the quality of anything you listen to, from zoom calls to podcasts. Only you can decide if that justifies the investment.

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