AMR AM-77

8th Mar 2008 | 11:57

AMR AM-77

A refreshing take on the integrated amplifier

TechRadar rating:

5 stars

AMR is a company with capability and vision and this shows in the design and performance of the AM-77 - it's a thrilling amplifier that brings you the dynamics of valves with the power of transistors in a substantial but well-featured design.

Like:

Offers a dynamic and revealing sound; High build quality, input labelling and gain adjust; Decent ancillaries

Dislike:

Inconveniently heavy; No preamp output; Volume change is slow - a rotary control would have been nicer to use

You wouldn't guess from looking at AMR's products that the company was started by a bunch of guys who were smitten by the sound of single-ended triode amplifiers, specifically those running 300B output valves.

There are two valves on the AM-77 amplifier, but they're a far cry from those that inform the company's sonic ethos. This is, therefore, a real-world company that understands you're never going to be able to start a serious business building amplifiers which have single-figure power outputs and radiate more heat than some electric fires.

AMR stands for Abbingdon Music Research, a name chosen because Abingdon (with one 'b') is where the British Motor Corporation took the humble Mini and turned it into a rally car that took on and beat the world; an inspirational name indeed.

The company isn't actually based in Abingdon; rather, its HQ is sited in London, while its manufacturing facility is located in China. Among its founders is occasional internet reviewer and hi-fi nut extraordinaire Thorsten Loesch, a man renowned for his knowledge of valve amplifiers and the guy who persuaded Stevens & Billington to build the Music First passive preamplifier with a transformer volume control (TVC).

To date, AMR has produced a CD player and an amplifier, and the company is in the process of finalising a loudspeaker to match - its aluminium casework meaning it'll match more literally than usual.

The AM-77 is a hybrid design using a valve gain stage (NOS 5687) to control a bi-polar output stage that runs in Class A and is specified as delivering 180 watts. This is the Fair Trade Commission (FTC) power rating, which is said to equate to the commonly quoted RMS spec used by most companies, but AMR also supplies an IHF peak rating of 270 watts to indicate the model's capabilities with a dynamic signal such as music.

The 180-watt figure applies whether the load is eight or four ohms, which will reveal to aficionados how similar this is to a valve amplifier; it operates just like a valve circuit, according to Loesch, but doesn't need an output transformer. AMR calls the whole circuit 'Class X', because it's neither pure Class A, nor AB throughout.

For an aspirational integrated amplifier, the AM-77 is unusually highly featured - for instance, it has both regular binding post and Speakon speaker cable terminals, plus both USB and mini-jack sockets on the side of the front panel.

Around the back are some mysterious switches marked 'mode' for which the manual must be consulted. These are included so you can bi-amp or bridge with more than one AM-77, or use it as solely as a power amp.

The final mystery switch is marked 'hi-fi/pro' and affects the way the XLR inputs are set up. With all hi-fi equipment and most pro equipment, the 'hi-fi' position is fine, but when you have a true floating transformer balanced output, you need to switch to the 'pro' position, because this requires a different connection.

Build quality appears to be exemplary, far higher than we've seen with Chinese-built kit so far - probably because most of the components are sourced elsewhere.

The mains transformer, for instance, is an enormous double C-core type that's hand-wound using grain-oriented silicon steel; this accounts for maybe 40 per cent of the mass. The existence of choke-regulation transformers explains another 10 per cent, and the rest is more or less accounted for by the 6mm-thick aluminium case and copper inner case.

There are PCBs in there too - quite a few of them, in fact - as our internal shot overleaf shows, and they have rounded corners to diffuse any resonance that manages to get that far.

With the model featuring touch-sensitive front buttons and a motion-sensitive remote handset, AMR seems to have thought of everything - even the RCA phono sockets are extremely high-quality. And we haven't even mentioned the chunky mains lead, high-quality interconnect (matching the internal wiring), flight case and two free CDs.

A couple of other useful features are 27 input options, including Home Theatre Direct, which has unity gain, and a +/- 6dB gain offset, so that different sources can be level-matched.

The AM-77 does indeed possess many of the attributes one would associate with a valve amplifier; and the music it produces certainly has that vitality and energy which only glass audio can deliver. It handles speed and dynamics without any edginess or glare, to such an extent that one is left in no doubt about the valve factor.

However, it also does something that valve amps can't unless they're partnered with a substantial, high-sensitivity loudspeaker: it delivers power. The AM-77 can drive a pair of B&W 802Ds to truly entertaining levels, and do it across the full bandwidth without bending the response too obviously.

In other words, that 180-watt figure is borne out in practice. The 802D isn't the easiest load - its impedance drops to 3.5 ohms and it has some nasty phase angles - yet the AM-77 can induce it to deliver some fabulously strong and timely bass lines.

Those produced by Robbie Shakespeare for Grace Jones' finest works, for instance, are delivered with a tunefulness and articulacy rarely enjoyed outside of the studio.

A pure solid-state 180-watt amplifier can produce a weightier sound than this model, and if it's a good one, it might be able to do the rhythm and timing bit too, but only the best can deliver the timbre of each note along with it.

The AM-77 isn't designed to be a powerhouse; it's designed to give as much valve sound quality as its makers can achieve within the context of useful power output, and it does a superb job of judging this balance.

It's only when you try to use the AM-77 in PA mode that its limitations become apparent; there's a degree of forwardness in the midrange that also relates to the valve factor.

So while it's perhaps not the best high-end choice for the Metallica fan, it would suit the Led Zeppelin enthusiast who owns reasonably efficient speakers and has a love of spacious soundstages. The degree to which this spaciousness manifests itself depends on the source and recording, but if there's acoustic space in the signal, the AM-77 will be sure to make the most of it.

Led Zep's How The West Was Won demonstrates this to full effect, with tremendous 'being there' atmosphere which, when combined with the dynamic capabilities of the amp, makes for an inspiring sound.

Timing is also a strong point, thanks to tremendous speed that means notes stop and start with pinpoint precision, be they high, mid or low-frequency. This is why the bass lines are so remarkably nimble and why all forms of music have a life force that's often obscured.

It'll be interesting to hear the AM-77 partnered with AMR's ribbon-tweeter-equipped speakers when they're finished - usually such drive units bring a finesse to the treble which domes struggle to emulate, and this would smooth the amp's balance when played hard.

Some recordings can get a little uncomfortable at high levels, but this does come back to AMR's tenet that this isn't supposed to be a powerhouse. It's just that the sound is so enticing, one can't help but wind it up. We guess that's why there are a variety of ways to use two AM-77s - a tasty prospect.

As it stands, this is a very exciting amplifier from a company that leaves no stone unturned in its quest for sonic revelation. Furthermore, AMR has managed to reconcile this quest with designing a well-thought-out product that should work well with a range of speakers - something that's much rarer indeed.

Hi-Fi/audioSpeakers
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