AudioQuest DragonFly Cobalt Review: Give Your Wired Headphones a Boost

A portable headphone amp might seem anachronistic in this age of Bluetooth headphones. Why be tethered to your phone when wireless is the future? While many Bluetooth headphones offer impressive sound quality, they're inherently limited in their design. Built-in batteries and electronics take up space and add to the overall cost. Many manufacturers of wired headphones and earbuds offer models that, in theory, cost the same as Bluetooth models but with better or more drivers. Other models have drivers that are too power-hungry to work well with built-in batteries.

7.2

AudioQuest DragonFly Cobalt

Like

• Tiny
• Powerful for its size

Don't like

• A bit expensive
• No adjustments or mobile app

You can power these wired headphones from any headphone jack, but built-in ports rarely have much power. Instead, a portable headphone amp can give audiophile headphones the juice they need without tying you to a chair or desk. 

Which brings us to the DragonFly Cobalt from AudioQuest. It's been out for a few years, but it's now 30% cheaper and in future it'll be the only model in the DragonFly line. Roughly the size of a thumb, it connects to any phone or computer via USB. Inside is an amp and a DAC, or digital-to-analog converter, that claim to elevate the listening experience. We shall see. Or hear. We shall hear. 

Specs, according to DragonFly

• DAC Chip: ESS ES9038Q2M
• Max sampling rate/frequency: 24-bit/96kHz
• Amp chip: ESS Sabre 9601
• Power: 2.1 volts, according to DragonFly

The Cobalt looks like a USB thumb drive. Included is a short dongle that converts the USB-A on the Cobalt to USB-C for use with phones and many laptops. To connect to iPhone 14 or below you will need a separate Lightning adapter. The AudioQuest also includes a small pleather case, which is a nice touch even if I don't imagine it will get much use.

Inside the Cobalt is a ESS Sabre 9601 headphone amp and a ESS ES9038Q2M DAC. The Cobalt maxes out at 24-bit/96kHz, which is less than some USB DACs. There isn't a ton of music available at higher rates, but there is some. Personally I think there is value in higher-than-CD sampling rates (16/44.1) but I'm skeptical of anyone who says they can hear a difference between 96 and 192kHz.

The claimed power rating of "2.1 volts" is unclear and practically misleading. Nearly all amplifiers are rated in watts and it's easily the most recognizable audio spec. Watts is volts multiplied by amps, and no device like this is putting out anything close to 1 amp. So no doubt "2.1" is far more impressive a number than whatever milliwatts this, or any, headphone amp provides. 

For comparison, the older and cheaper DragonFly Black listed its power as 1.2 volts. And the similar iFi Go Link says it has 70mW into 32 ohms and 2.05 volts into 600 ohms (which converts to 7mW). 

The dragonfly indicator on the DragonFly lights up in different colors with different sampling rates: Red for Standby, green for 44.1kHz, blue for 48kHz, yellow for 88.2kHz, light blue for 96kHz, and purple for MQA. At least, that's the theory. Rarely did this match up with the claimed sampling rates on audio I tested with my Pixel 7. It matched better, or at least faster, with my Sony NW-A306 portable media player.

Sound quality, tested and compared

I tested the Cobalt using some high-end pairs of headphones, two of which are borderline "portable" -- I don't think most people would walk around wearing them, at least. Those would be the Audeze LCD-3 ($1,945) and the Sendy Audio Apollo ($500). These headphones are made to be worn while sitting in one place and enjoying music. I also used the Meze Audio Rai Penta in-ear monitors ($1,100), which aren't particularly difficult to drive, but have excellent clarity. Why use expensive, and in two cases huge, headphones to test a $200 amp? Because if it can power these it can power just about anything. I used a mixture of CD-quality and high-resolution FLAC from Qobuz.

Not wanting to listen in a vacuum, so to speak, I compared the Cobalt to several other amp/DACs, starting with the headphone jack on my computer and then the analog output of my Pixel 7 via a USB-C to 1/8th analog dongle. I also compared the Cobalt to the iFi Audio hip-dac2. This is also technically a portable headphone amp, and priced similarly to the Cobalt. But it's much, much larger, and has a cumbersome connection process that I wouldn't expect most people to use walking around. 

When I compared the Cobalt with my (admittedly anemic) desktop PC's headphone jack using the LCD-3 headphones, the sound was fuller at the same volume level than without it. Percussion had a tighter, more immediate attack. Most notably, I was able to get a much higher volume with better bass using the Cobalt. With the PC's volume control all the way up, the sound was a little higher than typical listening volume. When I added the Cobalt, that same approximate volume was achieved with a setting around 60, with 75 being plenty loud and 100 being beyond comfortable. Not bad for a thumb drive-sized device and huge planar magnetic headphones. Admittedly, the sound at maximum wasn't as clean as it was at lower volumes.  

While wearing the Sendy Apollos I noticed better clarity with the Cobalt compared to the computer's built-in headphone jack. When I switched to my phone's output, via the dongle, the Apollos had fuller bass when played through the Cobalt, and sounded more open. Once again, volume was the biggest difference. With the volume control all the way up on my phone, the Apollos were just above what I'd call a normal listening volume. Through the Cobalt, however, maximum volume was louder than I'd listen to for any length of time. 

With the Rai Pentas, there was less of a noticeable difference. Despite their price and five-driver design, they're not particularly difficult to drive. So even the Pixel 7's dongle could drive them with enough volume. Was there a little more realism to the overtones and high frequencies with high-resolution tracks? Possibly. The glockenspiel at the start of Sloop John B (from the 24-bit, 192 kHz version of The Beach Boys' Pet Sounds) had a richer, more realistic timbre, for example, despite the Cobalt's downconversion to 96 kHz. It could have just been a slight change in the tonal balance, since the Rai Pentas have a more mellow sound with lesser amplifiers. I'm not sure I'd bet my house on a blind A-B test either way. The truth is, there is far less difference between modern DACs than everything else in the audio chain.

Lastly, I donned the LCD-3s again to compare the Cobalt to the iFi Audio hip-dac2. If you're looking for something that gives you better audio on the go, the hip-dac2 is probably too large. It's a bit smaller than a flask. That extra space includes beefier electronics, though, so if you usually listen at your desk or while seated, this is a potential alternative. Because of that, the hip-dac2 just has more power. Not only can it drive the LCD-3s louder, it sounds cleaner doing it. The hip-dac2 sounds less compressed at higher volumes. The difference isn't huge, but is noticeable back to back. 

Is it worth your money?

There are two questions that arise when reviewing a product like this. First, does it improve the sound over a reasonable baseline? Yes. With any hard-to-drive headphone, the Cobalt will absolutely sound better than a headphone jack or a cheap dongle. Even many easier-to-drive headphones will likely sound at least a little better (or, at the very least, louder). 

Second, does it perform well enough to justify its price? That's harder to say. Do you have headphones that either need an amp or will sound better with one? Do your usual sources limit the performance of your headphones? Since most computers and phones have terrible headphone amplifiers, dongle or not, the answer to that latter question is often yes. To the question of price, the DragonFly seems a little expensive. There are a wider variety of amp/DAC dongles like the Cobalt on the market now than there were when the DragonFlys first took flight. Many of them cost a lot less money. I'll be checking some out soon.

If you don't have headphones that can justify the price of a $200 accessory, this shouldn't be your first purchase. It's not going to make $50 headphones sound like $500 headphones. And if your headphones deserve an amp but you only ever use them while seated in one place, the hip-dac2 has a little better sound at the cost of portability and overall convenience. (The newer hip-dac 3 has a more convenient dual USB-C connection.)

That said, if you do fit in the above-outlined niche, the Cobalt impressed me more than I expected for its size. For something so small, it definitely improved the sound of some great-sounding headphones and it was exceptionally portable.

As well as covering audio and display tech, Geoff does photo tours of cool museums and locations around the world, including nuclear submarines, massive aircraft carriers, medieval castles, epic 10,000-mile road trips, and more.

He wrote a bestselling sci-fi novel about city-size submarines, and also Budget Travel for Dummies. You can follow him on Instagram and YouTube.