NAGRA - MSA power amplifier (11.01.2010)
A year ago, at the 2009 CES, the Nagra MSA transistor amplifier was presented as a prototype. Now the MSA is introduced to the market in its final version.
The Nagra MSA is a stereo power amplifier with 60 W per channel into 8 ohms output. The two channels can be parallel-bridged to reach a double mono output power of 120 watts RMS into 4 ohms. Casing of the MSA is faithful to the distinctive look and to the aesthetic standards of the brand. The front face is equipped with the traditional Nagra elements: the modulometer and the large rotating selector. The size of the Nagra MSA is consistent in width and depth (275 x 230 mm without connectors) with the Nagra PL-L, PL-P and VPS preamplifiers and also with the Nagra CD players family.
The generous heat sink mounted on the top of the unit is a machined single block of aluminium. The MSA relies on original Nagra solutions and on the experience from such amplifiers as MSA, PSA and PMA. PFC (with active correction) power supply is one of the important technical features. A 200W transformer and capacitors of 84.000uF are alos used. Power output stages are based on a double current transfer driver stage and a pair of MOSFET transistors per channel in a common source push-pull configuration with the output on the drains. This arrangement allows comfortable operation under any situation, with no trace of instability, even when running in parallel-bridged mode, with very low impedances loads.
The MSA feature a pair of balanced XLR inputs and gold-plated speaker terminals. There is also a switch provided to choose sensivity of either 1V or 2V. MSA can be turned on an off in a conventional manner, but it can also operate in an automatic mode, turning on upon detection of input signal or turning off after detecting that there is no input signal for more than 15 minutes. An array of sensors and surveillance circuits will detect any over-heating or output stage overload. As soon as an anomaly is detected, the control circuit deactivates all inputs and inhibits the power circuits. The MSA also hosts a soft-start switch-on circuit that makes sure the relays only start up a few seconds after the unit is powered up.
Nagra has also informed about the devlopment of an amplifier based the 300B tubes. A stereo push-pull integrated amplifier with 20W per channel is called Nagra 300i. The size of the Nagra 300i also conforms to that of the compact series. A power version, called 300p will follow the integrated amp. The launch of both versions of the 300B is planned for 2011.