You may think that Sonnet Digital Audio is a new name in the world of the true Hi-Fidelity and the digital technology, but it is only partially so. For sure, Sonnet it is a new brand, but it includes all the previously built-up know-how in Metrum Acoustics, with the most recent technological/product optimizations developed since mid-2018, when Cees Ruijtemberg left Metrum Acoustics to start Sonnet Digital Audio.
Who is Cees Ruijtemberg (Ed.)
Cees Ruijtenberg is the Dutch digital genius. After founded and developed Metrum Acoustics and after having produced some of the best DAC available today at extremely competitive prices, gifted with the most complete, balanced and deeply natural sound, today Cees presents with the top DAC Sonnet Morpheus the design of a further refined Metrum Pavane Level 3. You can hear the difference.
Our Kratos mono block amplifier differs in many respects compared to normal transistor power amps. When looking to available hybrid designs were tubes will drive the power output stage, soundwise Kratos will have lots of similarities. Like them Kratos has an airy and spacious sound but with the control and grip of a transistor amplifier. A disadvantage of these hybrids however is the problem of aging of the triodes. To avoid this problem for our Kratos a front end has been made with high voltage fet transistors. As a result, the measurable properties are completely identical compared to triodes, but having the advantages that no aging occurs. A similarity is the high operating voltage to get these circuits working. The result is a high degree of linearity. From this point on, the circuit drives a class A/B mosfet output stage. Only a small amount of feedback is needed to get the correct gain, but at the same time it also improves the damping factor. While a dedicated circuit for the high voltage is made, the output stage is powered from a heavy 400 Watts power supply.
In addition to manual control of the amplifier, it can also be controlled via a remote cable to our Morpheus dac. Another switchable option is the so-called "music sense" that checks the input for the presence of music and turns the power amplifier on. After half an hour of no information, this circuit will put the amplifier back into standby mode.
Protections are of course part of this design such as overcurrent, offset and overheating and are monitored in real time. All relevant information can be seen via a display on the front.
(Top side of Kratos, Power section with 400 Watts power supply)
(Bottom side of Kratos, High Voltage simulated triode section)
50 Watt into 8 Ohms, 95 Watt into 4 Ohms, 160W into 2 Ohms
Distortion 0.040% THD
Damping Factor >150
110/115V AC 220/230V AC 60/50Hz
Output Noise 350 µV RMS
Frequency Response 10 - 230.000 Hz – 3dB
Slew Rate 100V / µSec
Input Impedance RCA 15 KOhm, XLR 60 KOhm
Max Power consumption 400 Watt
Main Voltage 110/115V AC, 220/230V, 60/50Hz
Dimensions 290 x 250 x 60 mm