The Unico 100 integrated amplifier is quite a beast, it weighs a formidable 25 kilos and delivers a respectable 180 watts from each of its dual mono channels.

It does so without looking overly bulky, so it's an even greater shock when you first attempt to move it.

As the power output would suggest, the second half of the amplifier is the transistorised one, where three pairs of Mosfets are gathered in a parallel configuration (possibly as a result of its valve roots, Unison prefers to use multiple low- power devices rather than a few big ones).

Controlled performance

The preamplifier section is a double triode stage utilising a single ECC83/12AX7 valve, with special attention being given to the interface between glass and silicon.

Here Unison says it has used a topology that ensures regulation of the DC component of the signal without compromising performance at low frequencies. The digital volume control consists of an integrated circuit that uses an array of precision resistors combined with digitally controlled analogue switches.

The output level is indicated on the front panel display and has 99 steps that start at 0.0 and rise to 9.9. We found that even with the quietest discs and reasonably sensitive speakers, the numerical level never exceeded 2.5 and was usually in the 1.8 to 2.2 range.

This number is, of course, fairly abstract, but it would be more satisfactory if the control had been 'geared' so that you could at least approach 9.9.

Amp design

Switching it on elicits a 30 second countdown via the display, while the amplifier stabilises voltages. It takes somewhat longer to actually warm up, but produces plenty of heat when it's truly ready to play.

The two large fascia-mounted dials control volume and input selection, both also serve a function when pressed (mute and tape loop). Volume can also be adjusted with the system remote, a device that's largely hewn from solid wood and stands up like a cordless phone.

Connections consist of four single-ended and one balanced input, alongside tape and volume controlled sub outputs. These are in a mirrored arrangement that defies guesswork when attempting to hook it up in a dimly lit space!

Speaker terminals are doubled up for ease of bi-wiring and the casework is entirely aluminium which is very nicely executed and seldom seen at this price point.

Lively combo

Having manhandled this beast into a Custom Design Icon rack, we connected it up to a pair of PMC OB1i speakers that had been giving great service with another amplifier.

The combination is a lively one, perhaps too lively through the midband, this being an area where both components excel. And while the pairing is extremely open and well timed, it can get a little bit too forthright.

Bass lines are very clear cut with reasonable weight, but instruments nearer the midband are a little bit obvious in the mix. It's nice to hear all the air around them, but not if it starts to mask the lead voice in the music.

Strong timing

Switching over to a Leema Tucana integrated (around the same price), makes this imbalance more obvious with a more powerful and better timed result that seems rather more tonally even.

Conversely it does highlight the openness of the Unico 100 which is, undoubtedly, a reflection of the valve content of its preamp section. These may also help the timing, which although is not quite in the Tucana league is better than usual, something which enhances the enjoyment of all manner of music.

Moving the Unico over to a pair of Bowers and Wilkins 802D loudspeakers brings forth a more relaxed balance thanks to the relatively 'dark' nature of the midband on this speaker.

It is gratifing to hear that the Unico 100 can drive what is a fairly difficult, if reasonably sensitive load. The bass is a little softer than pure transistor designs produce, but it's weighty enough and has sufficient power.

This suggests that this twin transformer- powered amplifier has the sort of current delivery capabilities that the manufacturer's figures claim.

Smoother sounds

Cymbals are still pretty obvious in the mix of many recordings, but they are slightly softened which makes them much more palatable.

In fact, this is true of most metal instruments via this amp, in particular brass, which is easier to enjoy thanks to a subtle smoothing of peaks.

We found both instruments to be rather more listenable on the Yo Miles album Upriver, which is a bonus because the tendency is to tolerate them while waiting for Henry Kaiser to let rip with his Stratocaster and produce some truly filthy abstract blues.

In this instance, you can hear all of his noodlings rather more obviously as a result of the upper midband peak in response.

Entertaining system

The Unico 100 is a bit like the Linn Majik LP12, in that it sacrifices neutrality at the alter of musical engagement, – a worthy trade-off, albeit one that may not work for all musical genres.

Keith Jarrett's piano on his Carnegie Hall disc, for instance, lacks authority, but is seemingly more tuneful and enjoyable than usual.

Against this the coughs and splutters of the audience are more obvious, which some might find too high a price to pay. But the result is pretty captivating which, at the end of the day, is what good hi-fi should be about.

It is also possible that with careful loudspeaker and cable choice one could find a balance that is more even overall. Unison Research's own sister brand Opera should be the ideal partner for the job.

Whether they would also be able to solidify the slightly airy imaging qualities of the amplifier is a different question, but with greater efficiency the could bring out more of the energy; a good hi-fi dealer could advise on this.

The Unico 100 is a well-built amplifier that manages to combine many of the strengths of transistors and valves. It also boasts, in the context of a musically entertaining sound, a removal of harshness and a delivery of real power.