Pro-Ject’s compact integrated amplifiers, side by side. Here is the Stereo Box E alongside the models above it and their specifications, showing what your money buys at each step.

The Stereo Box E is the most affordable way into a Pro-Ject system, and it does a remarkable amount for its size. It is an ultra-compact integrated amplifier, small enough to sit on a desk or disappear on a shelf, yet it carries a moving-magnet phono stage, a digital-to-analogue converter, Bluetooth and a headphone amplifier, so it will take a turntable, a streamer, a television and a pair of headphones without anything else being added. It is not a powerful amplifier, and it is not built for a large room. It is the amplifier for a first proper system, a second room or a desktop, where the whole point is to get real hi-fi sound from as little space and money as possible.

Brief product overview

A compact Class D integrated amplifier delivering 21 watts per channel into 8 ohms, rising to 40 watts into 4 ohms, with fully analogue preamplifier and power amplifier stages so analogue sources are never unnecessarily converted. Connectivity is unusually generous for the size: a moving-magnet phono input with a grounding screw, suitable for moving-magnet, moving-iron and high-output moving-coil cartridges; an RCA line input and a 3.5mm input; two optical and one coaxial S/PDIF digital input feeding the built-in high-resolution DAC; and aptX HD-capable Bluetooth 5.0. There is a subwoofer output for adding bass later, a headphone output for private listening, and a 5V/1A USB-C output intended to power low-consumption streaming devices. The chassis is steel with a brushed aluminium front panel, 206mm wide and 51mm tall, in black or silver, and it matches the rest of Pro-Ject’s Box Design range.

How it sounds

The Stereo Box E sounds bigger than it looks. The fully analogue preamplifier keeps the sound clean and uncluttered, and the low-noise power stage gives a clear, lively presentation with a wider soundstage than a unit this size has any right to produce. Its 21 watts are modest, so it is at its best with efficient, sensibly sized speakers in a small or medium room rather than being asked to fill a large space, and it doubles its output into 4 ohms, which helps with speakers that dip lower. The onboard phono stage is a genuine one rather than a token gesture, and the built-in DAC handles digital sources cleanly, so the amplifier gives both a record player and a streamer a proper front end. It is an amplifier that removes the need for extra boxes at the start of a system.

What we’d partner it with

For speakers, the Stereo Box E’s 21 watts suit compact, efficient designs. We suggest the Pro-Ject Speaker Box 3 E, a two-way bass-reflex loudspeaker from the same Box Design family, small enough for a desktop or a bookshelf and voiced open without harshness, with gold-plated terminals and magnetic grilles. Good alternatives from brands we carry are stand-mounts from Wharfedale, Elac, Mission and Triangle, all of which work well at this power.

For vinyl, the built-in moving-magnet phono stage means a turntable connects directly, with no external phono stage needed. We suggest the Rega Planar 1, supplied with the moving-magnet Rega Carbon cartridge factory-fitted, so it plugs straight into the phono input; a Pro-Ject Debut EVO or a Technics deck partners equally well.

For streaming, we suggest the WiiM Pro, which brings streaming and its own DAC and offers a choice of connection: use its RCA analogue output into a line input, so the WiiM does the conversion, or feed the Stereo Box E’s optical or coaxial input and use the amplifier’s own DAC. One practical note: the WiiM Pro needs 5V at 1.5A or more, so use its own supplied adapter rather than the amplifier’s 1A USB-C output, which is intended for lower-consumption devices.

On cabling, use a well-made speaker cable of appropriate gauge for the run, terminated at the banana or spade terminals; AudioQuest and Chord are the cable brands we stock.

Who shouldn’t buy it

If your room is large or your speakers are inefficient, 21 watts will run short, and a more powerful Pro-Ject integrated such as the MaiA S3 is the better choice. If you want network streaming built into the amplifier itself, the Stereo Box E offers Bluetooth but not Wi-Fi streaming, so you would add a streamer, or look at a streaming amplifier such as the Uni Box S3. And if you run a low-output moving-coil cartridge, note the phono stage suits moving-magnet, moving-iron and high-output moving-coil types, so a low-output cartridge would need an external stage.

The Stereo Box E is small enough to sit almost anywhere, and it runs cool, though it still wants a little air around it. For vinyl, connect the turntable’s leads to the phono input and its earth wire to the grounding screw; the Rega Planar 1’s Carbon cartridge is moving-magnet, so nothing else is needed. For streaming, connect the WiiM Pro either by RCA to a line input, using the WiiM’s DAC, or by optical or coaxial to use the amplifier’s DAC, and power the WiiM from its own adapter, since it needs more current than the amplifier’s USB-C output provides. Place the Speaker Box 3 E on stands, a shelf or a desk, clear of the rear wall where you can, as the port fires backwards. The subwoofer output lets you add bass extension later.