Intro
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The Dutch brand Sonnet Digital Audio has visited us a couple of times now. The Dutch brand is increasingly making its mark on the international market. Especially the extraordinary Non-Oversampling (NOS) dacs are ‘to blame’. We ourselves at Alpha Audio have been using the Sonnet Morpheus and Pasithea as reference for some time now. Why? They sound exceptionally good and remain relatively affordable in “the grand scheme of things.” Today, however, no d/a converters but a set of monoblocks are in the rack. The Sonnet Digital Audio Kratos mono power amplifiers. Can this digital guru also convince us in terms of amplification? Let’s check it out!
Those who have been following Sonnet Digital Audio and Metrum Acoustics for some time know that the founder – Cees Ruijtenberg – has made amplifiers before. The Metrum Forte immediately comes to mind. This stereo power amplifier was tested and approved by us in 2017, but that’s already six years ago! How quickly time goes by.
However, Ruijtenberg went back to work on his circuit and not only refined it, he improved it in a number of ways. Originally, Ruijtenberg was looking for a way to recreate a kind of triode tube amplifier, but without the disadvantages of tubes. To do this, he devised an amplifier that combines a FET input stage with a MOSFET output stage.
The new Sonnet Kratos is now a fully balanced mono amplifier that delivers 50 watts into 8 Ohms and 95 watts into 4 Ohms. The Kratos goes futher than the Forte in several ways, and not just because of its separate design.
One substantial change is the brand new, superfast input transformer. This should provide even more resolution and dynamics. Another significant improvement is the wider bandwidth compared to that on the Forte.
Unlike tube amplifiers, the “damping factor” remains sufficiently high so that the amplifier always has a grip on the speaker, and there is almost no feedback with the Kratos. All these modifications, combined with some smaller tweaks, should take the original design to the next level. But off course, this needs to be seen.
Recognizable
The boxes themselves look modest and have the same (half-width) dimensions (29x25x6cm) as the dacs. They are available in black and silver. This not only saves on costs, but also creates a certain uniformity. Up front we see the standby button and the familiar small, light blue screen. This screen shows the temperature (the boxes get warm but not hot) and an indication that the amplifier is operational. If desired, the screen can be turned off completely so you are not distracted by the lights at night. The choice is yours.
At the back you can choose from either XLR or RCA inputs but you can only use one variant at a time. To switch, you have to slide a small switch at the bottom of the unit. Ditto for using the ‘Music Sense’ application that automatically turns off the Kratos amplifier after 30 minutes when it no longer receives a signal.
