Pro-Ject Uni Box S3 silver

Uni Box S3: the integrated streamer amplifier by Pro-Ject

A connected streamer and an analog amplifier rarely coexist in such a compact format. Pro-Ject combines both in an aluminum chassis barely 20 cm wide, using the proven architecture of the MaiA S3 for the amplification section and the WiiM OS system for the network section. On the menu: eight inputs including an MM phono input in the tradition of the brand’s in-house expertise, dual-band Wi-Fi, Bluetooth, and an HDMI eARC input for the TV.

Dual mono analog amplification

The preamplifier and power amplifier are entirely analog, with a dual mono design that separates the right and left channels. Usable power is rated at 2 x 23 W into 8 ohms and 2 x 40 W into 4 ohms (at 1% THD), with distortion measured at less than 0.05% at 10 W into 4 ohms. That is modest on paper. In practice, these watts are suitable for sensitive bookshelf speakers, nearfield monitors, or floorstanding speakers with decent efficiency in a reasonably sized room. For difficult loads or large, very open spaces, it is better to plan for a more comfortable power margin.

Volume control remains analog, managed by a motorized potentiometer that can be operated from the supplied remote control. Channel separation reaches -67 dB at 10 kHz, and the signal-to-noise ratio is 94 dB into 4 ohms.

One point that Pro-Ject highlights: analog sources connected to the line-level RCA inputs or to the phono input undergo no digital conversion. The signal from a turntable, CD player, or tuner remains in the analog domain from input to speaker terminals. There is one exception, however: when the analog source is streamed to another room on the multi-room network, digitization is then applied for wireless transmission.

Streaming and the Pro-Ject Home app

For the network section, Pro-Ject partnered with WiiM, whose operating system powers the Uni Box S3. The new Pro-Ject Home app, built on this foundation, manages Wi-Fi setup, the equalizer, volume, and multi-room functions. Spotify Connect, Tidal Connect, Qobuz, Amazon Music, Deezer, Napster, Pandora, and TuneIn are directly accessible. High-resolution playback goes up to 24-bit / 192 kHz via compatible services or a local library such as a NAS.

Dual-band Wi-Fi (2.4 and 5 GHz) supports 802.11 b/g/n/ac standards. Bluetooth 5.0 supports the SBC and AAC codecs. Digital-to-analog conversion relies on a Cirrus Logic CS4344, multi-bit Delta Sigma, connected to the coaxial and optical S/PDIF inputs.

The True Wireless Sending and Receiving function deserves a mention. It allows any input on the amplifier to be streamed to other compatible Pro-Ject devices throughout the house, including a turntable, CD player, or the TV’s audio output. Conversely, the Uni Box S3 can receive a stream from a remote source such as the T2 W turntable. The ecosystem logic makes perfect sense if several connected Pro-Ject products coexist.

Dense connectivity for this format

Eight inputs in total, which remains generous for a chassis of this size. Three are analog: two line-level RCA pairs and one moving magnet (MM) phono input in RCA, with high gain of 46 dB and low self-noise. Three are wired digital: one coaxial RCA and two optical Toslink, all capable of 24-bit / 192 kHz. The eighth is the Wi-Fi / Bluetooth input.

New on this model, the HDMI eARC input allows a TV to be connected directly and volume to be controlled with its remote. This works in a living-room setup where the Uni Box S3 handles both music and TV sound, without resorting to an optical adapter.

On the output side: a pair of gold-plated terminals accepting 4 mm banana plugs, spades, or bare wire; a 6.3 mm headphone jack output on the front panel (70 mW into 32 ohms at 1% THD); a variable RCA output usable as a pre-out to a subwoofer or a second-zone amplifier.

Technical specifications

Amplification

• Fully analog preamplifier and power amplifier design
• Dual mono design principle
• Output power: 2 x 23 W into 8 ohms, 2 x 40 W into 4 ohms (1% THD)
• Power amplifier: Texas Instruments TPA3221DDV
• Frequency response (20 Hz - 20 kHz): < 0.4 - 0.9 dB into 4 ohms
• Channel separation: -67 dB at 10 kHz
• Signal-to-noise ratio: 94 dB (9 dB A-weighted) into 4 ohms
• THD: < 0.05% at 10 W into 4 ohms
• Analog volume control with motorized potentiometer

Digital-to-analog conversion

• D/A converter: Cirrus Logic CS4344, 24-bit / 192 kHz Multi-bit Delta Sigma
• S/PDIF inputs supporting up to 24-bit and 192 kHz

Streaming and network connectivity

• Market-leading WiiM OS streaming technology
• Pro-Ject Home app (new)
• Expanded multi-room capabilities
• Pro-Ject True Wireless Sending and Receiving: stream any input to your network
• Wireless vinyl streaming from the T2 W
• Countless compatible streaming services: Spotify, Tidal, Amazon Music, Qobuz, Napster, Pandora, TuneIn, Deezer, and many more
• Tidal Connect, Spotify Connect, Qobuz, etc.
• Music streaming up to 24-bit / 192 kHz from streaming platforms or your own library
• Equalization functions included to personalize your sound experience
• Wireless connectivity: Wi-Fi 5, 802.11 b / g / n / ac, dual-band 2.4 GHz and 5 GHz, Bluetooth 5.0, SBC and AAC

Inputs

• 8 inputs in total
  • 3 analog inputs: 2 RCA line pairs, 1 MM phono input (RCA)
  • 3 digital inputs: 1 coaxial RCA, 2 optical Toslink
  • 1 TV eARC input (new)
  • 1 Wi-Fi / Bluetooth input
• High-quality MM phono input with very low noise and high gain (46 dB)

Outputs

• 6.3 mm jack headphone output
• Headphone amplifier: 70 mW into 32 ohms (1% THD)
• Variable output: 1 RCA pair for subwoofer or second-zone amplifier
• Gold-plated speaker connectors: 4 mm banana plugs, spades, or bare wire

Power supply

• Power supply: 20 V / 3 A DC; 100 - 240 V, 50 / 60 Hz
• Standby power consumption: < 0.5 W

Chassis and finish

• Rigid aluminum housing protecting against interference
• Available in silver or black
• Dimensions (W x H x D): 206 x 55 x 153 mm (176 mm with connectors)
• Weight: 1100 g without power supply

Included accessories

• Remote control for managing analog volume, changing input, and muting / unmuting