But not in this case. The CDE is a well judged design that has got it just right. Without being in any way obvious about it, this is, above all, a relaxed, easy-sounding and genuinely musical player that nevertheless gives a broad, expansive stereo image and an unusually positive impression of musical dynamics – never clipped or aggressive, but always cleanly articulated and always convincing.

Pure vocals

The easy on the ear quality is something that often comes as standard with valve electronics, but usually there is a price to pay. In this case, the achievement is just about seamless, the only possible and very mild criticism being a hint of softness at the very lowest frequency extreme.

The mid and treble are of a different order – fast, expressive and almost luxuriantly coloured at appropriate times. Strings for example sound distinctive and homogenous in an orchestral setting without being homogenised.

Vocals have a real passion and purity and piano has the right mix of percussiveness and sustain, retaining the authentic 'voice' or personality of the instrument. The end result: music reproduction that breathes, that sounds expressive and that simply gells.

It took about three A-B comparison runs between the two DAcs before we quite suddenly achieved these results. The upgrade DAC sounds (tonally, at least) in many ways similar to the standard model, presumably because so many of the audio components and sections are shared.

But the upgrade DAC, in fact, has a clearly superior instrumental and vocal separation, giving a feel of greater contrast and range and for this reason a superior impression of dynamic shadings, especially in more subtle, undemonstrative musical passages that don't naturally show high levels of internal contrast.

Performance passion

The bass, too is just right, if arguably not quite as authoritative as the best of solid-state as implied earlier, but the mid and high frequencies are notably sweet and pure.

This was clearly audible in a recently acquired disc of Grieg, including the evocative music used as the soundtrack for the recent Joanna Lumley TV programme about the Northern Lights.

Through the Unico CDE, the music, which when reproduced with less distinction can sound hackneyed, sang with an understated, but still very real passion that made the hairs on the back of the neck rise.

There were similar experience on offer with other recordings, one very good example of which was the second movement and the vocal finale from the excellent Bernard Haitink/Royal Concertgebouw orchestra version of Mahler's 4th symphony. In both cases and with a number of other recordings, too the sense of a living, breathing sound stage was palpable.

Well-priced deck

There's a feeling among many hi-fi devotees that valves often lead to a lazy attitude to design – which does many things superficially right, but when push comes to shove often doesn't work. This player is the opposite: a design based on a clear understanding of what valves can and can't do and which doesn't fall for the usual pratfalls.

The Unison Research Unico CDE is, in short, an excellent player, well built, well priced and one that plays music extremely well, with great purity, expressiveness and range, irrespective of its enabling technology.

And it benefits from an unusually welcome degree of flexibility, thanks to the upgrade able DAC option from the factory plus its ability to act as a simple, high-quality D/A converter for external digital sources.