The dongle DAC has become a familiar but awkward sight plugged into the bottom of a smartphone, a small reminder that the headphone jack didn’t disappear quietly. Portable audio has come a long way in sound quality, but the form factor hasn’t kept pace. Most of these tiny dongles hang loose from the charging port, tugging at cables and generally getting in the way of an otherwise pleasant listening session.
Fosi Audio’s MD3 MagDac tries to solve this with a fundamentally different approach to portability. Instead of hanging from a charging port, it snaps magnetically to the back of a MagSafe-compatible smartphone using 16 N52 magnets, sitting flush against the device like a compact audio module. The result is a pocket-sized DAC and headphone amplifier that actually looks like it belongs there, not like an afterthought.
Designer: Fosi Audio
The design doesn’t stop at clever attachment. The MD3 is precision-machined from 6063 aluminum alloy with a sandblasted anodized finish, available in silver or black, both with orange leather on the magnetic back. At just 50g and 12m thick, it slides in and out of a pocket without protest. What you’ll notice first, though, is the 1.28-inch circular LCD display on the back.
That screen handles volume in 100 steps, shows audio information, and rotates its orientation depending on how you’re holding the device. There’s also a Vista Button that opens a personal photo album, a small but unexpectedly human touch for a piece of audio hardware. A dedicated Ease Button and physical navigation controls keep everything accessible without ever needing to tap your phone’s screen.
For the audio itself, Fosi didn’t compromise on components. The MD3 uses the ESS Sabre ES9039Q2M DAC chip paired with four ES9603Q amplifier chips in a true balanced circuit, supporting PCM up to 32-bit/384kHz and native DSD256. Total harmonic distortion and noise sit at just 0.00075%, and the noise floor drops to 1.7 μV. For most IEMs and portable headphones, those figures translate to noticeably cleaner, more resolving sound.
The MD3 offers both a 3.5mm single-ended output and a 4.4mm balanced output, delivering up to 180 mW through the latter, enough for headphones ranging from 16 to 300 ohms. An aluminum alloy shielding plate sits between the magnets and the audio circuitry to prevent interference from coloring the signal, a careful engineering detail that keeps the magnetic attachment trick from undermining the whole point of the device.
Dual USB-C ports handle both audio and charging simultaneously, so you’re not forced to choose between listening and keeping your phone powered. The top port handles audio decoding and charging, while the bottom manages audio decoding and firmware updates. There’s also a volume memory feature, so the MD3 picks up at the same level every time you connect it, without having to reset anything.
The wired audio revival has been building for a while, drawing listeners who want something more intentional than Bluetooth. A magnetic DAC that attaches to the back of your phone without cables or cases seems like a sensible next step in making that experience practical. Fosi has been laying the groundwork quietly, and at $149.99, the MD3 might just be the portable amp that finally stays out of the drawer.
