Jadis JA120 Mono Power Amplifiers (Hi-Fi+ 90)

In these days of Global Warming, environmental sensitivity and the rapid evolution of highly efficient Class D amplifiers of diminutive dimensions and seemingly improbable rated outputs, one’s forced to wonder whether there’s really a place for amps like the Jadis JA120? In fact, if you wanted to define the audio equivalent of an electrical dinosaur, you could do worse than start with one of these French mono-blocs: over two feet long, a foot wide and another foot high, and weighing in at a far from cool 100 lbs, it would qualify on grounds of physical dimensions alone. Add to that no fewer than six output tubes a side, with a constant current draw of around 250 Watts, all required to produce a comparatively modest 100 Watt output – as well as a lot of heat – and high efficiency and environmental concerns are clearly not top of the product design agenda.

The JA120 uses the new KT120 tube. But Jadis have done more than just look at more powerful output tubes. There is an additional front-end tube, adding more gain to the driver circuit at the expense of increased complexity, while fuseable resistors now protect the audio circuits should an output tube fail. These look just like a 20mm fuse – and are just as easy to replace. In addition to these steps, the power pendulum has swung the other way, meaning that the JA120 only claims 100 Watts from its six output tubes, running them well inside the comfort zone.

So, what about the output transformer? Many years ago, I interviewed Andre Calnette, the founder of Jadis, and he suggested that 90% of the sound of any valve amp is down to its output transformer. Which probably explains why the company takes the unusual step of winding all its transformers in-house. Indeed, they are very much a house speciality and the hand-wound designs have been steadily refined over the years. Combine that with the revised driver arrangements and the JA120 sits at the pinnacle of the company’s current thinking; if there was ever an argument for oodles of glass driven Class A power then this should be it…

Just as the output tubes are used conservatively, that rated output should also be considered conservative. In use, the JA120s deliver just the sort of power I’ve always lusted after from the marque. If to these ears the 80s sounded sluggish and the 100s lack the immediacy of the 30, neither complaint can be leveled at the 120. This amp is big, bold, dynamic and when necessary, dictatorial – in the best Jadis tradition. What’s even better is that getting it to play ball is simplicity itself, as long as you follow a few simple rules. The first and most important is that you will probably want to lift the earth connection on one of the power cords to avoid a ground loop. Secondly, in my experience the Jadis amps work best on short interconnect driving long speaker cables and this latest model is no exception. If you must run long cables there is a balanced input option and I’d certainly consider it. Running single-ended, shorter interconnects bring a welcome immediacy and clarity to the sound which recedes as the leads get longer.

Eagle eyed readers will have noticed the twin sets of output terminals. That’s exactly what they are; not alternative impedance taps from the transformer. To match the amplifiers’ impedance to the speaker, you need to remove the bottom of the chassis and rearrange a set of metal jumpers. This might seem like a chore, but it’s generally a one off operation and when it comes to transformers, if that’s the way Jadis want it done, I’m not going to argue. But don’t overlook this adjustment just because it isn’t external. The other thing the amplifiers benefit from is proper support; adding mechanical coupling to bypass the rubber feet provided a welcome boost in focus, transparency and low-level resolution.

Power is a deceptive quality. There are plenty of amplifiers out there, boasting prodigious power outputs on paper, yet in practice, they never seem to deliver. Conversely, there are other amplifiers that belie their modest paper specifications and produce performances with real musical impact and presence. One of the reasons that I always loved the JA30 was their ability to punch above their weight. It was a quality that seemed to diminish as the Jadis amps got more powerful, but the JA120s have sorted that failing once and for all. Real musical power isn’t just about Watts – although they certainly help. It’s about how many of them get where they need to be, and just how quickly they can do it. It’s about presence, weight and the ability to jump when the music demands it, and together they add up to drama and impact. The trick is to deliver that, but to master subtlety and delicacy too – and that’s where the 120s really score.