In a very real way, this is the easiest review I’ve ever had to write. The Audio Research Reference 160 S is the stereo version of the Reference 160M mono power amplifiers we reviewed in Issue 163. The 160 S is cheaper and takes up less floorspace but offers almost all the qualities of the 160 M, save the obvious channel separation that mono amps bring and a very slight reduction in ‘edge of the limits’ range and scale brought about by a shared chassis. Unless you like to play at ‘noise abatement’ levels or have a particularly demanding block of iron masquerading as a loudspeaker, you might never notice. We loved the 160 M, and the 160 S does nothing to tarnish that feeling. There. Job done!
OK, so it’s not quite that simple, and neither was it quite that simple for Audio Research to take a perfectly fine mono valve power amplifier and squidge (technical term) it down into a single chassis. Or, more correctly, it’s not so easy to turn mono amps into a stereo amplifier without throwing the baby out with the bathwater. Often, the sacrifice is substantial and while the product still makes it out into the wild, it does so at the expense of performance… and we’re all canny enough to recognise the shortcomings. The reviews are good, but not the same kind of ‘rave’ of the original model, sales are mixed, and history doesn’t treat the ‘stretched’ or ‘shrunken’ model kindly. Fortunately, Audio Research has a gift for not doing that at all. In the case of the Reference 160 S, it took the popular 160 M and made sure the 160 S had the same basic voicing, in the process consciously moving the mild shortcomings such a change makes to places where few will notice or care.
The Reference 160 S replicates almost everything of the 160 M in not-quite microcosm, including a proprietary auto-bias circuit, switchable Triode or Ultralinear modes of operation, balanced and single-ended inputs, a choice of speaker output taps, and an output tube monitoring mode. It also sports two matched pairs of KT-150 power output turning in a healthy 140W – which are fed by two 6H30 double-triodes in the gain stage – per channel. That’s exactly the same gain-stage and output valve configuration found in the mono amps. The mono amps have their own chassis and their own power supplies, where in the 160 S both of these are commoned and fed by a huge C19 IEC connector.
The other big thing that’s retained is the GhostMeter front panel display, where the twin VU meters on the front of the amplifier ‘float’ within the glass front. In print, this can sometimes look as if it is part-obscured by the glowing glass behind it, or it looks as if it glows too brightly. In fact, neither of these things are true in the real world, and – although it’s probably more an ‘ankle up’ than a ‘head up’ display, the GhostMeter really looks the part, ladling on the retro-cool to the point where you might want to play some John Barry soundtracks. More importantly, it can also act as a useful status display board for the amp’s health and tube hours.