Audio Research Reference 6 line preamplifier

The last time I reviewed an Audio Research component—it was the VTM200 monoblock amplifier in January 2001—my hair was mostly dark brown. The wait since has been not of my choosing, but that's now flux under the circuit board. Since then, much has happened to both me and to the Audio Research Corporation, a long-lived company for which the descriptor "legendary" is well deserved.

William Z. Johnson founded ARC in 1970, in Minneapolis (the company later moved to Plymouth, Minnesota). He passed away 41 years later, on December 10, 2011. In an interview published in the August 1994 issue of Stereophile, Johnson, who was also ARC's chief engineer and was rightly credited with single-handedly reintroducing vacuum tubes to high-end audio, said this of his designs of the 1970s:

"I tried transistors, but I thought the sound that I was able to generate with various design approaches was horrendous—it was terrible. Then when FETs came along, I tried again. And while we were able to design circuits with some relatively good numbers, the sound quality still wasn't there. As the years went by, of course, that tended to change. Since then, we've made some inroads with both bipolars and FETs. Today I would have to say that our various solid-state products are probably superior to the early tube units.

"In saying that, however, it's still true that, with an all-out design effort, vacuum tubes will win. . . . [Younger readers should know that in the early days of ARC, the idea of designing by listening as opposed to solely by measuring was a radical concept.—MF]

"[T]he measurement techniques we use today really don't necessarily tell you about the sound quality. Obviously, if it measures badly, it isn't going to sound good. But the simple fact that it measures well doesn't assure that it will sound good."

In 2008, three years before his death, Johnson sold ARC to Fine Sounds, a subsidiary of the Italian private equity fund Quadrivio, which also owned McIntosh Laboratories, Sonus Faber, Sumiko, and Wadia Digital. Quadrivio subsequently sold Fine Sounds to its current owners, Mauro Grange and Charlie Randall, who renamed the company The McIntosh Group. The acquisition seems to have been good for ARC and for its loyal, worldwide fan base.

Livio Cucuzza, chief industrial designer for the entire McIntosh Group—his father was an Audio Research dealer in Italy—redesigned ARC's entire line, modernizing the look while retaining some classic Audio Research elements. The results are, in my opinion, eye-catching, though some complained about the "plastic" knobs. But the knobs aren't plastic: they're made of a black-anodized aluminum that's difficult to produce and is sourced overseas. (Almost all other parts used in ARC products, other than the tubes, are made in the US, much of it in or near Minnesota.) Whether you prefer the bold new look or the older, hospital-instrument aesthetic is a matter of taste. I like the new look. More important, based on the Reference 6 ($14,000)—introduced last year, and a major upgrade of the Reference 5 SE—ARC seems able to invest in serious upgrades of casework, circuits, and parts without significantly raising the price.


Audio Research products are designed by a team led by director of engineering Ward Fiebiger, a 37-year ARC veteran, and Dennis Petrich, who's been with the company since 2008. Warren Gehl is in charge of "sonic development." Gehl takes seriously William Johnson's adage: "the simple fact that it measures well doesn't assure that it will sound good." Working with the engineers, Warren helps "tune" the sound of each new model. He not only passes judgment on every new ARC design, he listens to every ARC product before it leaves the factory (footnote 1).

Operating System
Installing a new component in an audio system is like bringing home a new puppy. Sometimes, the addition fits in as if it's always been there; other times, accommodating it requires a lot of time and effort. Some gear I've installed has immediately improved the system's sound—or, at least, provided a perspective on the music just as valid if different from that of the component it replaced. Other gear has required changes up and down the chain to bring the system back into pleasing balance (footnote 2).

ARC's Reference 6, run in balanced mode, slipped into my system like a fully house-trained puppy. Its sound was different from that of my reference preamp, a darTZeel NHB-18NS—either the original (most recently priced at CHF31,700, approximately $32,665 by today's exchange rates) or the all-new ($39,500) version, soon to be reviewed—but within a few tracks its contributions seemed to slip under my radar, reappearing only when I began to take serious note of its qualities both positive (most of them) and negative.

Replacing the Reference 5 SE ($12,995), introduced in 2011, the Reference 6 has circuits so heavily revised from its predecessor's that there's little point in comparing them, other than to say that everything has been upgraded and enhanced, including a more massive power transformer, an improved volume control circuit, and newly developed custom capacitors. The audio circuit includes three 6H30 dual-triode tubes per channel; the power supply has one 6H30 and one 6550WE tube.

A great deal of attention has been paid to the design of the new, massive, custom-machined aluminum enclosure, which has unusually massive side panels—all of which is intended to act as an energy sink to drain away internally created vibrations.

On the front panel are two large, encoder-controlled rotary knobs, for Input (left) and Volume (right). Input selects among the eight inputs, the names of which can be customized; Volume adjusts the loudness in 103 steps. Between the knobs is a large fluorescent display, and below that are six smaller pushbuttons, from left to right: Power, Menu, Enter, Mono, Invert, and Mute.


On the large rear panel are four pairs each of balanced (XLR) and single-ended (RCA) inputs, two pairs each of balanced (XLR) and single-ended (RCA) outputs, and balanced and single-ended Record Outs. There are also IR input and 12V trigger outs, an RS-232 connector, a fuse bay, and a 20-amp IEC mains jack. All is laid out cleanly; the jacks are generously spaced, to accept even the widest-diameter RCA plugs. The rear panel is spacious and easy to use.

The menu system includes some really useful options. You can set up the Reference 6 to remember a different volume setting for each input, or have it reset all inputs to zero when powered off. You can name the inputs or leave them with their default numbers. And because the software remembers the level settings and you can switch inputs from the remote control, running A/B comparisons is really easy.

The display is easy to read, even from across the room. When you push the Mute button, "Mute" appears in large letters directly above that button. Ditto with Invert (inverts absolute phase) and Mono. This seems a no-brainer, but not all displays present their components' functions so clearly. In terms of setup and use, the Reference 6 proved a total pleasure.

Some old-school Audio Research fans preferred the maze of knobs and toggle switches found on such vintage models as the legendary SP-11, from the mid-1980s, which then cost $5000 (including two-input phono section). But today, with software, so much more can be done more simply, and with less smudging of the signal path.

The aluminum remote-control handset is nicely machined and well laid out. It provides complete control over every front-panel function, plus Balance, Display Brightness Up/Down/Off, and Hours, which displays how many hours the tubes have been run. In the old days, you either kept a log of this information, or changed tubes with neurotic frequency because you'd lost your log, or never kept one.

Some say that the ideal preamplifier is a "straight wire with attenuation/gain" that efficiently routes the audio signal from the various inputs. Others—I'm one of them—have concluded that because ideals do not exist in the real world, the best preamp is the one that minimally alters the sound, and whose minimal alterations are themselves subtly pleasing in ways that may even enhance the sound qualities of the system's other components.

Footnote 1: To meet the Audio Research staff, take a virtual tour of the factory, and see how ARC components are manufactured and evaluated, visit my YouTube channel to watch part 1 and part 2 of my recent, informative, and mirth-filled visit.—Michael Fremer

Footnote 2: This is not necessarily a bad thing. See my review of the SAE 2HP-D power amplifier in the October 2016 issue.—Michael Fremer

Audio Research Corporation
3900 Annapolis Lane N.
Plymouth, MN 55447-5447
(763) 577-9700

A. Hourst's picture

“That may offend the sensibilities of those purists who demand absolute accuracy, but in audio, there's really no such thing”

I don’t know what’s most funny: Michael Fremer who thinks he can “offend the sensibilities” of some objectivists, or the fact that he thinks this will happen from such an empty, predictable commonplace as the “immeasurability” of good sound.
There’s really no such thing, you say, as absolute accuracy in audio. Never mind the fact that the usual tenants of a “good enough” accuracy only ask it to be better than the human ear sensitivity, which is rather easily achieved with modern electronics, Mr Fremer don’t even recognize “absolute accuracy” as an existing horizon in audio. Absolute accuracy conceptually exists in audio as much as it exists in photography or in watchmaking. However, if someone is trying to push a 14 000$ piece of electronic whose performance can be bought for less than 1/10th the price, rising up the confusion by saying things like “in audio, there’s really no such thing as absolute accuracy” can be good practice.
One thing will never happen: a blind ABX comparison of this ARC preamp with a 1000$ similarly measuring one, to put to the test this idea that dollars can get you what measurements and science can’t.

ChrisS's picture

And has never happened, because a blind test in this situation is not practical nor very useful.

ChrisS's picture that you acknowledge that you are the only one who keeps asking for something that will never be done!

Are you the only one who needs to have your idea tested?

Allen Fant's picture

Great review- MF.
until I can demo the new Ref6, I feel the Ref5SE, is still the best tubed pre-amp in the ARC arsenal.'s picture

Absolutely well written. Yes the Reference 6 is all that and more. Even the new Foundation Series LS28 betters the Reference 5 SE now.
Yes Casework and other improvements have trickled down to the Foundation series.

Vade Forrester's picture

This was one of the best reviews I've ever read. Well done, Michael.

Vade Forrester
Reviewer, SoundStage! Network and The Absolute Sound
My words=my thoughts.

WJ ARMSTRONG's picture

I agree with my fellow reviewer Vade Forrester - this was unusually entertaining and successfully conveyed some quite subtle notions with a lovely light-touch clarity. Almost as enjoyable as listening indeed!
Thanks Michael.
Bill Armstrong - 6moons

jsch123's picture

I own it and it's lovely. The best preamp I've ever owned and it's really brought me to a point of finality . I mean, not really because I'll be tinkering for the rest of my life, but it could easily be finality. If that's even a word.

I agree with just about everything MF said. Especially the "a lot of meat on its bones". But you know it remains exceptionally open and transparent and dynamic at the same time. It's just lovely. Gone is ALL the grain. Smokes both my VAC preamps.