Mola Mola has announced a new mono power amplifier called the Ossetra. The Ossetra is relatively compact but, thanks to its “Trajectum” Class-D amplifier technology, can deliver 350 watts into eight ohms.
Mola Mola Ossetra
Mola Mola describes its proprietary Trajectum topology as a discrete interpretation of Class D. The designers essentially moved much of the gain into specially designed Class A stages and combined that with a full-bridge output and a wide-bandwidth feedback loop. According to Mola Mola, the result is a preservation of Class D efficiency while simultaneously reducing noise and distortion.
The Ossetra has a maximum power output of 350 watts into eight ohms. At four ohms, this is 700 watts, and if the load were to drop to two ohms, 900 watts would be available. The specified S/N ratio is 130 dB. The bandwidth is greater than 100 kHz.
Key engineering changes include a redesigned power supply that, according to the company, significantly exceeds regulatory limits in terms of EMI performance, reduces noise, and improves both dynamic and continuous output power. These power supply improvements are matched to an output stage described as a significantly higher current-carrying amplifier, making the amplifier easier to drive under heavy speaker loads.
Mola Mola has opted for a full-bridge output topology for the Ossetra, which, according to the company, maintains a balanced signal path from input to output and reduces some secondary power supply requirements. First, the company implemented all-new discrete Class A amplification stages, designed with a high open-loop bandwidth and positioned to carry a large portion of the amplifier’s total gain. According to the company, this revised amplification structure allows for increased feedback around the output stage without the usual drawbacks, resulting in reduced system noise and distortion.
The input stage is DC-coupled by default, with no capacitors in the signal path. According to the manufacturer, this avoids the sonic compromises that capacitors can cause. However, there is a pragmatic compatibility measure: at higher signal levels, a capacitor is added to the path to accommodate third-party preamplifiers that do not tolerate DC coupling. Mola Mola also highlights new shunt voltage regulators placed close to the input stage. These are said to improve noise rejection, reduce local output impedance, and keep the AC current local to the load.
Mola Mola claims the Ossetra exhibits minimal load dependence, which should ensure consistent frequency response across varying speaker impedances. The output impedance is less than 0.002 ohms, resulting in a damping factor of over 4,000. This allows the Ossetra to drive virtually any speaker without difficulty, even those with erratic impedance variations.
