Audio Research LS27 Preamplifier/Reference 75 Power Amplifier (Hi-Fi+)

Equipment report
Tubed power amplifiers,
Tubed preamplifiers
Audio Research LS27 Preamplifier,
Audio Research Reference 75
Audio Research LS27 Preamplifier/Reference 75 Power Amplifier (Hi-Fi+)

There’s an odd – but altogether understandable – sense of reverence and respect that falls upon Audio Research’s Reference series of products. In today’s market, that has an obvious downside; people only tend to use Reference products with other Reference products. While that’s an easy way of getting excellent results, it’s not the only way.

The new Reference 75 power amplifier is a perfect example of this dissociated thinking. Yes, of course it sounds fine on the end of an all Reference system (NOLA’s excellent demonstration of the KO loudspeaker at RMAF used the Reference 8 CD player, Reference 5 preamp and the Ref 75 amp, to ‘best in show’ winning effect). But it also sounds excellent when used with the LS27 preamp (in fact, this test was going to go a rung lower and use a LS17 SE, but this preamp was out on demonstration at the time of review).

The new star of the show is the Reference 75, a balanced only, stereo valve power amp delivering – as you might expect – 75 watts per channel, from a brace of KT120 power tubes per side, all in a case about the size of one Reference 150 chassis. It’s a dual mono design, with only the power transformer and solid-state regulation shared to both channels. The power supply and its dozen storage capacitors take up a single board to the centre of the chassis, with the identical power amp PCBs (complete with a JFET input stage, a 6H30 driver tube and a pair of KT120s) either side.

The front has two power meters, that glow light blue if you flip the switch at the back, and a 12V trigger if you want to power the tube amp up with the preamp. The front panel has an on-off main switch and two front screw bias controls, one per channel; flip between them and the centre ‘operate’ position to have the KT120s running perfectly. It uses a 20A power cord (supplied).

It’s met here by the LS27 line only preamplifier. This one-box, remotely controllable pre replaced the LS26 that we loved so much we gave it an award. Like its predecessor, it uses a hybrid JFET/valve circuit featuring a pair of 6H30 dual triodes as input drivers. It’s both balanced and single-ended in operation and can switch between the two with alacrity. It has a nice large ‘no need for reading glasses’ display (as opposed to the cataract-proof super-sized displays of the Reference 5 and now two-box Reference 10). It’s the archetypal good ARC preamp: easy to use, good sounding, a combination of refinement and detail.

ARC recommends a 600 hour break in on all products now. The pre arrived with enough miles on the clock, the power amp was new out of the box. I don’t think I’ve even got remotely near the 600 hours yet. I don’t mind or care. It’s good enough. If the caps bed in still more, it should reach an even happier place than it currently does, but almost from the moment those tubes were inserted and the biasing finished, the magic happened.

There has always been an ARC ‘sound’; a midrange that is remarkably clean and clear, a bass that rivals the best in the world for depth (if not for speed), good dynamics and a mid/top-end bloom that is always attractive. Little wonder that some of the best loudspeakers in the world ended up being used with ARC, both in homes and in test facilities.

But there was a fly in the ointment; the smaller power amps (with a few notable exceptions, like the VSi60) haven’t had the same authoritative sound as the big ones. Ever since some of the classic ARC amps like the D79, smaller amps have had a power delivery akin to trying to blow out a candle while yawning; the energy was there but the dynamism was lacking. The Reference 75 brings large-scale ARC thwack to a more down to earth level, without sacrificing the qualities of grace, poise, clarity and scale inherent to ARC designs.

But lets start with the LS27. It’s a truly great piece of equipment. It has an ability to disappear in the way all good preamps are supposed to do, and does so with outstanding image size and width. That means it’s resolving enough to highlight details in changes elsewhere up-stream, yet does not lay the sound so analytically bare as to devastate the chances of it ever sounding good. It’s been some time since I reviewed an ARC preamp and it’s clear the performance has moved ahead several notches since last I set my system’s watch to Minnesota time. It’s kind of in a sweet-spot musically; not so unresolving as to smooth over the cracks in the music, not so resolving as to highlight the wrinkles. A happy Goldilocks.

And it has a perfect partner in the Reference 75. It’s a siren of an amplifier, seducing all who listen to it, whether they are tube types or solid-state specialists. Starting with a simple test – Tony Bennett and Bill Evans – the sense of presence projected that wonderful vocal into the room, all the while giving the tonal beauty and energy to Evans piano playing. It was a masterful presentation of a masterful piece of singing and playing that never gets the coverage it deserves. I stayed on the simple side and played Harvest by Neil Young from his recent Official Release series box set. On the painful ‘The Needle and The Damage Done’ from Harvest, and the syncopated guitar part should be easy to reproduce, but frequently isn’t. On the Ref 75, it becomes a natural down-beat to accent the anguish written into those lyrics.

I moved onto rock, dance (James Blake’s cool dubstep sounds particularly potent through the Ref 75) and through the full spectrum of classical music, from delicate string quartets to Solti throwing an orchestra and choir through its Mahler paces. Nothing phased the Ref 75. Practically nothing phased the LS27 either but really nothing troubled the Ref 75 at all. Imagine an amp that combines the grace and liquidity of tubes with the speed and temporal precision of a good solid state and you begin to see why the Ref 75 is so special. Quite simply, this is valve mastery!

I briefly swapped out the LS27 for a Music First Baby Reference passive magnetic preamp for an upcoming test. This proved a fascinating experience; the two went toe-to-toe for the most part, the MFA having the edge in terms of musical focus and solidity, the LS27 winning the day when it came down to resolving the most complex pieces of music. But this experiment confirmed two things; how close to neutral (and a passive preamp practically defines ‘neutral’) the LS27 really is and just how good that Reference 75 sounds on almost anything. It’s one of those rare products that comes with no real downsides, as long as you are not desperate for more power.

And at this point, the Ref 75 invites a difficult question of the listener. Do you need more than this? The answer is frequently ‘no’, especially in places like the UK where real estate is at such a high premium. That it can drive comparatively difficult loads with ease makes it the kind of device that seems more powerful than its output suggests. The result it delivers has won over at least one UK reviewer who bought the review sample, and it’s doing a fine job in converting this one to the cause too. Although the LS27 is an excellent preamp, and a fine match for the Reference 75, the latter is in a class of its own. Decades from now, audiophiles will remember this power amp in the same hushed tones as we now bestow upon classic ARC products like the D79. Only thing is… I think this might be better than the lot of them.

Three conclusions fall out of this. First, the difference between ‘standard’ and Reference Audio Research is noted, but proves no impediment to producing good sound from combinations of components. Next, the hackneyed transistors vs. tubes, single-ended vs. balanced petty wars are in essence valueless; it’s just good stuff versus not so good stuff, and there’s a lot of good stuff here. Which brings me onto the final conclusion; we are living in a golden age of audio. We need to stop living in the past; this current crop of products sound better in some very fundamental ways to any of the sacred cows of the past. In valve world, it gets no better than this.


LS27 line preamplifier
Inputs: Eight (XLR and RCA)
Outputs: Three (XLR and RCA), two main, one record, 12v trigger
Valve Compliment: 2x 6H30
Dimensions (WxHxD): 48x13.4x37.6cm
Weight: 7.4kg
Price: £6,498

Reference 75 power amplifier
Inputs: XLR only, 12v trigger
Outputs: multiway posts, 4 ohm and eight ohm taps
Power output: 75W per channel
Frequency response: 0.7Hz-75kHz (±3dB)
Valve Compliment: 2x 6H30, 4x KT120
Dimensions (WxHxD): 48.3x22.2x53.3cm
Weight: 21.3kg
Price: £8,495

Manufactured by: Audio Research

Distributed by: Absolute Sounds
Tel: +44(0)208 971 3909

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