Pro-Ject Uni Box S3 Black

A Compact Streaming Amplifier in the Pro-Ject Hierarchy

The Uni Box S3 sits comfortably between the entry-level Stereo Box E and the more powerful MaiA DS3 in Pro-Ject's integrated amplifier range, offering a well-judged step up in features and connectivity without moving into the premium tier. Built to Pro-Ject's customary standard of European manufacture, it brings together a clean analogue circuit design and a full WiiM streaming platform in a compact enclosure that will suit a desktop, bookshelf, or secondary system equally well. At its price point it represents a thoughtful package for listeners who want both a capable phono stage and a modern streaming front end in a single box.

Fully Analogue at Heart, with WiiM Streaming Built In

Pro-Ject's key design decision with the Uni Box S3 is that analogue sources are never digitised. Signals from the phono MM input and the two stereo RCA line inputs travel through a wholly analogue pre and power amplifier stage, with a Texas Instruments TPA3221DDV delivering 2 x 23 watts at 8 ohms (40 watts at 4 ohms). The headphone output provides 70mW into 32 ohms for private listening. Streaming is handled separately by the WiiM OS platform, which uses a Cirrus Logic CS4344 DAC capable of 24-bit/192kHz playback. Any source connected to the amplifier can also be streamed wirelessly to other WiiM-compatible devices on the same network, which makes the unit a useful hub in a multi-room setup.

Connectivity and Everyday Usability

Inputs cover the main digital formats: RCA coaxial, two optical TOSLINK sockets, and eARC alongside Wi-Fi 5 (dual-band 2.4GHz and 5GHz) and Bluetooth 5.0 with SBC and AAC codec support. A variable RCA output enables integration with a powered subwoofer or a secondary amplifier. Speaker terminals accept 4mm banana plugs, spade connectors, or bare wire. The power supply runs from a 20V/3A DC adapter accepting 100 to 240V at 50 or 60Hz, and standby consumption is below 0.5 watts. Dimensions are a modest 206 x 55 x 153mm (176mm including rear sockets), with a total weight of 1,100g. The Uni Box S3 is also available in Silver.