Audio Research Corporation Reference 160M Monoblock Amplifier

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Equipment report
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Tubed power amplifiers
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ARC Reference 160M
Audio Research Corporation Reference 160M Monoblock Amplifier

Since I first heard William Zane Johnson’s D76 stereo amplifier and SP3 full-function preamp back in the early 1970s, I’ve been a fan of Audio Research electronics. Indeed, I’ve owned and reviewed more gear from ARC than from any other marque. So, you may well ask, why haven’t I written about anything new from my all-time-favorite firm in the past several years? Well…I have my reasons. (And the folks at ARC doubtlessly have theirs.)

Speaking for myself, my first consideration was the reference speakers I’ve been using, which for the last decade or so have been various Magicos. Now, it is not as if Magicos fare more poorly with tube electronics than other dynamic loudspeakers; they don’t. But they are low enough in sensitivity, difficult enough in load, and demanding enough in power delivery to make big solid-state amplifiers somewhat better matches—particularly big solid-state amplifiers from innovative companies such as Soulution and Constellation, both of whose products have the sort of untrammeled current, iron grip, and very low distortion that make Alon Wolf’s speakers sound their best.

Second, the latest Swiss and American solid-state gear, particularly the gear from Soulution, is now capable of reproducing a quality that I value highly and that used to be the sole provenance of tubes (and of ARC tubes par excellence). To wit, while an amp like the Soulution 711 may not have the bloom or midband transparency of classic ARC, it does image in three dimensions, which is not something you could say of most transistor amps in the past. HP’s bon mot (taken from Coleridge) about the flatness of instruments on digital recordings—“painted ships upon a painted ocean”—could just as easily (and accurately) have been applied to instruments played back on most solid-state amps. Today, that isn’t as true as it once was.

Finally, there is the bottom end. Tubes typically don’t have the grip, speed, and extension of solid-state in the bass octaves, and with tricky-to-drive, sealed-cabinet speakers like Magicos, that grip, speed, and extension are indispensable if you want to hear the actual notes a Fender bass is playing, rather than mere blots of color that rise and fall with pitch like mercury in a thermometer.

None of this is to say that today’s solid-state gear casts shade on the glories of Audio Research. Indeed, part of the reason I’m reviewing the company’s newest amplifier, the 140W Reference 160M monoblock, is because I was reminded of those glories at RMAF last fall, where I heard the Reference 160M driving Sonus faber’s Aida II four-way floorstander. As I said in my show report, “Although I’m a lifelong fan of Audio Research, it’s been a while since I’ve heard the company’s latest offerings. Given the magic the 160Ms and the Ref 6 [preamp] performed with the Aidas (speakers I haven’t always loved in the past), I’m clearly missing out on something exceptional. On every LP I played, from Chet Baker to Enescu, this was the best demo of the show—and not by a little bit. The Sonus/ARC/Clearaudio combo simply had more of the breath and bloom of life than any other exhibit.”

Breath and bloom. These have always been ARC’s signal virtues. No other gear, tube or solid-state, reproduces voices, trumpets, saxes, clarinets, violins, guitars, anything that plays primarily in the midrange with the same remarkably realistic sense of air being moved past lips, through the mouthpieces, tubes, and bells of brasses, through the reeds and pipes of winds, and from the strings and bodies of violins and guitars. Combined with a sui generis bloom that makes sounded notes seem to swell three-dimensionally, as if they are riding on the surface of an expanding sphere rather than flattening out in a single plane, ARC’s airiness has given it an edge in sonic realism from go.

Of course, that isn’t to say that classic ARC excelled everywhere it played. Audio Research gear, preamplification and amplification, has never had the grip or the discernment of solid-state in the bass; it has almost always added a little energy in the upper mids, a bit of roll-off on the very top, and a touch of suckout or leanness in the power range; and in spite of its nonpareil midband transparency, it has also added a soft graininess to the entire soundfield. Over the years, ARC has improved voicing in all of the areas I’ve just mentioned, but never really eliminated these characteristics, only ameliorated them. Until now.

Which brings me to ARC’s latest (and in some regards, greatest) amplifier, the Reference 160M monoblock. 

I should start by saying that if you’re expecting, as I rather was after hearing the Reference 160M and the Reference 6 preamp driving those surprisingly excellent Sonus faber speakers at RMAF, that familiar, bright, lively, intensely bloomy, midrange-centric ARC sound, you are going to be a little surprised and, initially perhaps, put off—at least if you’re using the amp in its standard Ultralinear mode. In fundamental ways the 160M doesn’t sound like any other ARC amp I’ve heard or reviewed. Oh, there are definite family resemblances, but in overall tonal balance, in bass response, in imaging, and even to some extent in bloom and resolution, this is a different creature than William Zane Johnson’s designs.

Of course, the REF160M should sound different since so much about it is a departure from classic ARC. To begin with, its output tubes are no longer GE 6550 pentodes. In the REF160M ARC is using Russian KT150 power beam tetrodes, with 6H30 drivers and solid-state regulation of the (much stiffer) power supply. (ARC started using KT150s to power its amps in the mid-2010s, not only for sonic reasons but because of their availability and, according to ARC, durability.) 

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