Pre/Power Amplifiers

This should have been the simplest, swiftest review for me to undertake: I would simply drop the stereo version of the Audio Research Reference 160M [HFN Aug '18] into my system in place of the Reference 75SE. Double the number of KT150s and double the power, a price tag of two quid shy of twenty grand, fond memories of the monoblocks still tugging at me after 18 months: the Audio Research Reference 160S should have been a doddle, easy to anticipate. But it wasn't.

It has been Audio Research's practice to deliver stereo versions of its monoblocks after a suitable passing of time. In theory, the differences should relate solely to general monoblock-vs-stereo amp arguments: total isolation of left-and-right channels and separate AC sources for both, versus shared elements in the stereo edition. But here it's not straightforward because the new model – hitherto called the REF160S – is almost too good.

Dandy Triode
At first glance, this looks to be exactly what a stereo version should be: same rating, but a single chassis and a massive cost saving – roughly 30%. Otherwise, it's the same in operation and practice, again with the pain of valve housekeeping reduced thanks to auto-bias and the delicious user option of switchable Ultralinear and Triode operation on the fly.

But this calls for a moment's digression, as I champion the KT150. Over the years, I have been drawn to a handful of output valves, including the KT77, 211, 845, and I am no more ashamed than those who worship the 300B triode. But just as the 6550/KT88 became the de facto tube for most makers, as did the EL34 decades before, the KT150 has become a modern classic. Moreover, Audio Research truly knows how to apply it – as I found when moving from the REF75 [HFN Nov '12] to REF75SE. With REF160M or S, we find it also makes a dandy triode.

As editor PM counselled me, 'Triode mode offers half the power and fractionally less distortion here, but how does it sound?'. Once again, I wish there was armchair remote selection available here, but I still found the choosing of Ultralinear-vs-Triode to be source-, genre-, system- and political-bias-dependent, but that's simplifying it too much. As I said, my initial thoughts that this review would prove to be a doddle were swiftly crushed.

It was gonna be a breeze – dig out my notes for the 160M review, same music. But in the interim, I had changed from Wilson Yvettes [HFN Feb '17] to Sasha DAWs [HFN Mar '19], acquired the TechDAS Air Force III Premium turntable [HFN Jun '19] and changed all wiring to Transparent. So I had to approach this with fresh ears.

Two Into One Will Go
Installation was utterly straightforward. The rear of the amp is fitted with stout 4mm binding posts with nominal 16, 8 and 4ohm taps and an array of toggles to select single-ended or balanced inputs, fan speed and auto-shut off. Tube hours are indicated on the back.

Initially, I didn't even bother to check whether I was in Triode or Ultralinear mode, the power differences between the two never an issue for me as I'm no headbanger. I couldn't wait to hear the thing but impatience is an ugly trait, and switch-on involved the usual waiting for the unit to settle down and come out of its mute condition. I was chomping at the bit. Those two minutes or so seemed an eternity...

It was worth it, for what issued forth was so extreme a jump in performance that I immediately thought about selling my wine cellar so I could acquire a REF160S of my own. As there had been so many changes to my system since I reviewed the monoblocks, I threw out the notion of using the same LPs and CDs in an attempt at repeating precisely the same test. Instead, I trusted my ears (and hundreds of hours with the rest of the system) to decipher the charms and merits of the REF160S. And it started with the bass.