In the last few years, by far the most successful hybrid amplifier design to come my way has been the Trilogy Audio Systems 995R, that company’s flagship mono-bloc. It succeeds largely through an innovative circuit that couples a 6H6P-based voltage gain-stage to a compound output-stage, with small Mosfets at the input and multiple bi-polar devices delivering the current – enough current to pump out 50 Watts in Class A, 200 Watts in Class AB. It’s an arrangement that leverages the strengths of each individual element, the linear voltage gain and emphatic dynamics of the 6H6P tube, the impedance match between it and the Mosfets, the ability of the bi-polar devices to drive complex loads – a causal chain that plays directly into the amps’ purposeful sense of musical presence and authority. Operating mode is three-way switchable (A, AB or ecoA – which reduces bias current to the output stage when there’s no signal) and styling and build quality are as impressive as the amps are visually imposing. But what the 995Rs are not, is cheap: at €56K a pair (including 20%sales tax) the bill is as gulp inducing as the amplifier’s weight…
Which brings me to the subject of this review, the 994 mono power amp, paired with the 914 line-stage, an amplifier combination that embody the innovative hybrid ethos outlined above. With an all-tube line-stage and tube/solid-state power amplifiers, you don’t get much more hybrid than this, but let’s start with the 994 power amps.
The same width as the flagship 995R, the narrow but deep chassis of the 994 is around an inch-and-a-half shorter in height and nearly four-inches less when it comes to depth. Where the 995R looks statuesque, the 994 looks squat, solid and powerful, an impression heightened by the heat-sink slots carved into the face of the massive front-panel. If this amp was a fighter, it would be Marvin Hagler rather than Sugar-Ray Leonard: if it was a drummer, it would be Mickah ‘Don’t F**k With Me’ Wallace. It’s an aesthetic dominated by the massive fascia which, the best part of three-inches thick and carved from solid aluminium, contributes mightily to each amp’s 25kg (55lb) weight. More than just a heat-sink, its sheer mass gives the 994 significant thermal stability, the importance of which more and more designers are coming to appreciate.
Sitting on three-feet, the ‘shoe-box’ footprint of the 994 makes a pair easy to accommodate on a single shelf or amp stand, while the handed symmetry of the front-panels makes the arrangement look planned. If you do place the amps in a rack, just give the heat-sinks some air above them. Run these amps in Class A (if my experience is anything to go by, that’s exactly what you’ll want to do) and those front-panels will get plenty hot. Small LEDs display power-on and operating mode, just in case the cosy warmth of your listening room isn’t indicator enough. Which makes it time to talk ecoA. A simple push button on the rear of each amplifier changes its operating mode, cycling between A, ANB and ecoA, which saves on electricity. An LED on the back indicates which mode you are in, while the front LED runs solid blue for Class A, off for AB or pulsing blue (in the absence of signal) for ecoA. It’s the latter which most listeners will opt for – especially if you get clever with the 914’s timer settings – of which more below.
