DACs — Fosi Audio DS3

The DS3 is a pocket-sized USB-C headphone amplifier with an onboard digital-to-analogue converter, made by Fosi Audio, a dongle placed in the cable path from a phone, tablet or laptop to the headphones. It pairs an ESS ES9039Q2M conversion chip with an XMOS interface processor and follows the older DS1 and DS2 in the maker's range of portable converters. Fosi lists it at USD 99.99 in two colour versions called Obsidian and Galaxy.

Key specs that matter

PCM playback runs up to 32 bit and 768 kHz, and native DSD is accepted up to DSD512. The rated SNR is 122 dB or better and total harmonic distortion below 0.0003 percent. Maximum output reaches 220 mW into 32 ohm from the 4.4 mm balanced jack, and a 3.5 mm single-ended socket sits beside it. The output impedance is under 0.3 ohm, and the supported headphone load spans 16 to 300 ohm. A high and low gain toggle is set by pressing both volume keys briefly. The body measures 55 x 20 x 11 mm and weighs 16 g.

Engineering and use context

The case is CNC-machined from aerospace-grade aluminium alloy, which adds rigidity and carries heat away from the circuit, and a tempered glass panel framed by an orange bezel leaves the board visible. Two USB audio class modes are available. UAC 2.0 is the standard high-resolution mode for computers and phones, while UAC 1.0 is intended for consoles and gaming, with a virtual 7.1 spatial reconstruction and an FPS mode for game audio. Eight digital filter options, including minimum phase and linear phase types, can be selected, and a browser-based control panel from Fosi offers parametric EQ, filter choice and an option to switch the status LED off. Volume memory keeps the last level for each mode. The package includes a USB-C cable, a USB-C to USB-A adapter, a user manual and a quick guide, and the maker covers the unit with a 24-month warranty.

Pairing

Given its moderate output power and rated load range, the DS3 is best matched with in-ear monitors and headphones of moderate impedance rather than inefficient planar models. The USB-A adapter allows use with laptops and desktop computers that lack USB-C ports, and the UAC 1.0 mode lets it plug into gaming consoles that do not accept class 2 audio devices. Sensitive in-ear monitors benefit from the low gain setting and the very low output impedance.

Alternatives

The Fosi Audio DS2 is a related USB-C dongle built on two Cirrus Logic CS43131 chips, with the same pair of single-ended and balanced outputs and decoding up to DSD256.