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This review appears in the #1-2017 issue of Audio Esoterica magazine. The full text is below, but for a complete presentation we recommend clicking the image above or right to download a free PDF of the original article. You can see the full contents of this issue here, or to buy the complete digital edition of Audio Esoterica, click here.
This writer recalls meeting the legendary, yet ever so modest, William Z. Johnson when he travelled to Australia in the mid-1990s to launch what were, at the time, Audio Research Corporation’s new flagship monoblocs, the original and now legendary Reference 600s. I lusted after these monos, loved the retro design, and admired the construction and engineering within the enormous twin chassis. Then there were those gorgeous meters…

Alas, at the time, while starting a new business, funds were channelled towards what was to be the means for putting bread on the table. But just to appease the unbearable desire to own even just a modest item, a humble piece, from this American audio icon, I sought out and acquired an affordable pre-loved SP9 MKII preamp, proudly adding it to our then budding high-end system. And although inferior to the classic SP10 or SP11 preamplifiers, my treasured SP9 MKII sounded glorious, clear evidence of the company’s expertise in circuit design right down to the entry level.

Personally, of course, things have moved on, as they have for Audio Research, which has sustained its product excellence, now as a member of the Italian McIntosh Group, also owners of McIntosh, Sonus faber, Sumiko and Wadia.

The new Reference 6 is Audio Research’s flagship single-chassis preamplifier, encompassing the company’s latest thinking in circuit topology while now also enjoying the embellishment and industrial design flair of McIntosh Group’s Livio Cucuzza. (Only the two-box Reference 10, a special edition model, has not been updated to the new Cucuzza family aesthetic, which now includes the recently-launched Foundation series.)

And you can see, Cucuzza has full respect for classic Audio Research design in the Reference 6’s indisputably retro look, especially when looking at the 60s’ style input and volume knobs. Subjectively, this is an attractive design balancing classic and contemporary elements to create pleasing visual harmony. Nerdy as it may seem, equal pleasure can be derived by peering through the clear acrylic top (as provided on our review sample) and examining the competence and solid engineering behind the circuit layout and internal construction.

Audio Research Reference 6

As per tradition with Audio Research preamplifiers, the Reference 6 features a whole swag of connectivity in four line-level inputs available via both single-ended RCA and balanced XLR. Ditto RCA and XLR for the three output options (two main outputs and a ‘Record Output’) with a processor loop assignable via the menu. An RS-232 D-connector allows control, while trigger in/out mini-jack sockets can be used to activate other Audio Research components. A 15-amp IEC socket rounds out the rear panel connectivity.

The front panel features a large dark glass window with a comprehensive fluorescent display highlighted by a large (easy to see from the sweet spot) volume numeral. The display also constantly shows the chosen input (inputs can be independently named and volume levels set after turn-on) while a number of brightness options can be selected via the small but solid remote control. It’s a full-function remote too, with small buttons for standby on/off, input selection, phase invert, mono switching, menu access, dimmer up/down, left/right balance, of volume up/down and mute, of course, and ‘Hour Count’, a most useful function for monitoring valve life, used in AR gear for some time now.

On either side of the display, from left to right, are the input and volume knobs, while below is a row of metal buttons for Power, Menu, Enter (used in conjunction with the menu options), Mono, Invert and Mute. The ubiquitous AR handles finish off the nicely brushed aluminium fascia and the unit is available both in silver or black.

The key specifications are a wide frequency response from 0.4Hz to 200kHz at +0-3dB, gain of 12dB balanced and 6dB unbalanced and an output impedance of 600 ohms balanced and 300 ohms unbalanced. There’s quite a bit of glass too with six 6H30Ps for the line stage plus an additional 6H30P and a 6550WE for the power supply stage.

Audio Research Reference 6

Across a few generations now, the Audio Research house sound has been one of neutrality, powerful bass tied in with good dynamic expression, and an ever-so-subtle valve sweetness (in varying degrees depending on the individual component). The Reference 6 continues the narrative but adds a level of transparency beyond that offered by the company’s previous preamps (this writer has spent considerable time with the excellent Reference 5 SE). This was striking from the get-go, and the Ref 6 was toe-to-toe with an in-house passive preamp with absolute minimalism and ultimate transparency as its raison d’être. This ‘transparency’ characteristic is manifest in the Ref 6’s stunning levels of detail retrieval, in a balanced way that does not enhance or over-emphasise any frequency band. So the net result is not only extraordinary musical information in terms of detail and microdynamics, but also accuracy in tonality. Piano decay was also a notable aspect time and again when auditioning recordings of appropriate quality. Peter McGrath’s superb recording at Carnegie Hall with Earl Wild at the keys floored me with its intense palpability of the event – audience coughs and all. The Ref 6 just captures the hall’s ambience allowing the decay of the piano to be fully expressed. This of course adds to the overall realism with both instruments and vocals having a lifelike presence.

Audio Research Reference 6 And boy, can this preamp swing dynamics! Tony Dagradi’s Live at the Columns is a benchmark in dynamic contrast and the Ref 6 made this recording… quite scary. There was an expressiveness to this trio’s virtuosity (sax, acoustic bass and percussion) that will challenge your amplifier and speakers’ dynamic and power capabilities – especially in the several drum solos across this live recording.

While the Ref 6 proved adept at dynamic expression, there was equal prowess in bass power and control. In fact, subjectively, here’s another benchmark in bass quality – the Ref 6’s low-end is the best I’ve experienced from a valve preamplifier. It’s tight, deep, detailed, punchy and dynamic, and provides bass guitar, acoustic bass, kick drum and the like with toe-tapping and gut-pounding pure joy. Even Jackson Browne’s excellent but somewhat overcooked-in-the-bass Naked Ride Home CD, with its forward and abyss-deep (unnatural but oh-so-fun) low-end on “Sergio Leone” sounded controlled and almost back in balance – but retaining the fun. Depending on the room and speaker interaction, of course, the soundstage rendered with the Ref 6 in situ can span across and beyond the speakers with an image slightly forward of that plane and with very good focus. Image depth is along the lines of good valve preamplification, if not at the leading edge.

Somehow Audio Research manages to outdo itself on every occasion – at least in the last few generations of Reference series preamplifiers. The Reference 5 SE was among the very best preamps on the market, yet the Reference 6 takes it to another level.

To qualify this, the Ref 6 is substantially more transparent than its predecessor – you really hear into the recording (as an enthusiast and reader of these pages, I’m sure you know what I mean) – and thoroughly overshadows it when it comes to macro-dynamic expression and bass power and control.

By having the Audio Research Reference 6 preamplifier within the context of your system you’ll feel well confident that it will never be the bottleneck inhibiting your stereo’s full musical expression.

Audio Research Reference 6

Price: $22,995

Frequency response: +0-3dB, 0.4Hz to 200kHz at rated output (balanced, 200k ohms load)
Distortion: Less than .01% at 2V RMS BAL output
Crosstalk: -88dB or better at 1kHz and 10kHz
Gain: Main output: 12dB balanced output, 6dB SE output. Record out: 0dB (processor input: 0dB balanced output)
Input impedance: 120kohms balanced, 60kohms SE. Inputs: 4 balanced, 4 single-ended. Assignable processor pass-through
Output impedance: 600 ohms balanced, 300 ohms SE Main (2). 20kohms minimum load and 2000pF maximum capacitance
Inputs: 4 × XLR, 4 × RCA
Outputs: 2 × main, 1 × record out (XLR and RCA connectors)
Output polarity: Non-inverting
Tube complement: 6 × 6H30P dual triodes, plus 1 × 6550WE & 1 × 6H30P in power supply
Dimensions (WHD): 480 × 198 × 419mm
Weight: 17kg
Warranty: Three years, 90 days on valves