Our pick
The Fosi Audio DS1 is about the size of a domino, yet it has enough power to get maximum performance from all but the most demanding headphones. This amp has a simple design with balanced and unbalanced headphone outputs on top, plus volume controls on the side.
The DS1 is powered off your mobile device via its USB-C port, and our testing showed that the battery drain is not significant. The amp’s metal enclosure and detachable USB-C cable should make the DS1 rugged enough for years of use.
The main downside is that the DS1’s volume buttons don’t sync with your mobile device’s volume controls. You have to adjust the two separately. However, since the amp remembers your previous volume setting each time you connect it, this isn’t that big of a problem.
Budget pick
If you don’t want to spend more than $50, the Shanling UA1 Plus puts out plenty of power to drive most mainstream headphones, and it’s one of the smallest amp/DACs we’ve tested.
The UA1 Plus is powered off your mobile device via its USB-C port, and it has a single button to control playback and volume. Shanling’s helpful Eddict mobile app lets you fine-tune the channel balance and volume and choose between five different digital filters to change the sound profile (an option many audiophiles like).
The downsides are that the UA1 Plus lacks a balanced headphone output and the volume control is clumsy to use—though you can easily control the volume from your mobile device instead.
Upgrade pick
The iFi Hip-dac 3 is a whole different animal than our other picks. It’s much bulkier, but it’ll give you a few more clicks of volume than our top pick can, and it can run off its own internal, rechargeable battery—so it won’t drain your phone’s battery.
The Hip-dac 3 has both balanced and unbalanced headphone outputs, two USB-C ports, a bass-boost feature, and an old-fashioned (although comfortable, intuitive, and fast) volume knob. It’s the only one of our picks that includes MQA audio decoding, a controversial technology embraced by some audiophiles.
The downside is that the Hip-dac 3 is almost as large and heavy as a typical smartphone, so it probably makes sense only if you own a very power-hungry set of headphones or if you want to preserve every last minute of your phone’s battery life.
Also great
If you want one device that can serve as a Bluetooth headphone adapter when you’re on the go and a USB amp/DAC when you’re not, the Qudelix-5K is an excellent and surprisingly versatile choice.
This Bluetooth receiver supports all of the leading Bluetooth codecs, offers balanced and unbalanced headphone outputs, has impressive power output, and works with a mobile app that provides a lot of advanced adjustments.
The unit has a built-in battery that charges via its USB-C port, as well as controls for volume, track skip, play/pause, and pairing (which we found a bit confusing to use). You can read more about its performance as a Bluetooth headphone adapter in this guide.