Our Verdict 
Yet another superb design from Unison Research. Great to use and even better to listen to 
For 
Sonic delicacy and insight
Impressive refinement and dynamic fluidity
Terrific build
Distinctive look
Against 
Needs careful system matching
Reviewed on

Italian manufacturer Unison Research marks its 25th anniversary with three new products: special editions of the Simply Two and Absolute 845 (arguably the company’s most iconic products to date), as well as a homage to its first integrated amplifier, the Triode 20.

Design

But don’t let this fool you, the Triode 25 is no throwback. It’s a thoroughly modern valve-integrated amplifier with some interesting features.

You can even buy a version with a built-in DAC (for an extra £150), although our review sample isn’t so equipped.

On the surface, this line-level integrated amplifier is little different from much of the valve-based competition, featuring as it does, a preamp section with a pair of ECC83 valves and a quartet of EL34s to drive the speakers.

Yet, have a closer look, and Unison Research delivers a number of interesting twists to the established formula.

The Triode 25 can be switched from Pentode to Triode mode at the flick of a switch, even while you’re listening to music.

Pentode and Triode refers to the configuration the output valves work in – and switching between the two settings gives a distinct change of character to the 25. In Pentode mode, the power output is 45 watts per channel.

This gives the amplifier enough grip to work well with a relatively wide range of speakers, though we still wouldn’t necessarily partner this integrated with something insensitive in a large room.

But most sensibly selected speakers, in a small to medium-sized room (say less than 25sq m), can be driven to decent, if not quite head-banging, levels.

In this configuration, this Unison Research sounds controlled, relatively neutral and nicely detailed. There’s still the fluidity that people associate with valve products but here it’s coupled to much of the dynamic grip transistor-based alternatives are capable of.

Performance

Play Prince’s Sign ‘O’ The Times and the 25 is happy to punch out the beats, making a decent fist of communicating the song’s jittery, rhythmic drive.

Prince’s vocals are precisely drawn, and delivered with all the insight and nuance we’d hope for. This amplifier pulls ahead of rivals in its ability to render voices with convincing texture and delicacy.

There’s an undeniable naturalness to the way it does this that makes even talented competition such as Roksan’s Caspian M2 sound a little mechanical in comparison.

Move on to more delicate music and this integrated sounds even more at home. Given something like PJ Harvey’s White Chalk, it responds with the kind of finesse that makes us wonder whether it’s worth spending more.

There’s plenty of detail here, and the kind of fluid dynamics and full-bodied balance that has us listening for hours.

Flick the little chrome toggle switch between the valves to the Triode setting and two things happen: power output drops to 22 watts per channel and the sonic presentation becomes even more graceful.

There are losses in terms of grip and bass punch, and possibly even outright precision. But the upside is a more spacious sound with some notable gains in refinement.

More after the break

The Triode 25 is a relatively simple unit, but has a decent range of level connections. A built-in DAC is a £150 option

Listening to the amplifier in Triode mode is a beguiling experience that works brilliantly with gentler music. Given a small-scale classical piece or some easy-going jazz, the Triode setting would be our first choice.

If you have a wider music collection, the Pentode option is more of an all-rounder. It’s more tolerant of speaker choice too. The ability to tweak doesn’t end there.

The level of feedback used in the circuit can also be changed between two options (5dB and 1.8dB) with the flick of a switch. We tend to prefer the low setting due to its more expressive dynamics and increased level of fluidity.

The choice could be affected by the partnering system though, so it’s well worth experimenting here.

Build quality

We wish the buttons on the remote were more responsive and better shaped

Move away from sound quality and there’s still much to admire here. Build quality is up to Unison Research’s usual high standards – the Triode 25 feels like a solid, well-made unit and it’s finished well.

All the controls feel suitably chunky and operate with precision. We even like the wooden-cased remote handset, although we wish the buttons on the system remote were more responsive in feel – and better shaped.

Valve amplifiers need more maintenance than transistor alternatives. The larger power amplifier valves (EL34s) will tend to need replacement before their smaller counterparts.

Factor in changing the set of valves (around £140) every five-to-seven years (depending on use).

Each valve’s bias current will need adjustment periodically too. In most designs, this involves messing about in the circuitry with a multimeter and screwdriver, but with this design, it’s done easily using the built-in gauge and adjustment controls.

The left and right banks of valves are selected separately with a switch – just adjust until the pointer is dead centre between the green and red markings.

While we find the exposed valves quite attractive, they do run hot and those with young children or pets may need to make use of the supplied cover. It’s relatively attractive as such things go, though, and is easily removed if you need to do so.

Verdict

Unison Research’s track record with sensibly priced valve amplifiers is second to none. The Triode 25 is yet another strong performer that marries fine sound and distinctive aesthetics with pleasing build.

If you value subtlety and finesse above all else, there are few better alternatives at this price.

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