Dan D'Agostino
Momentum S250 Stereo Amplifier
The Momentum S250 stereo amplifier delivers the extraordinary sound quality of the Momentum M400 monoblock in a more affordable stereo design. The circuit topology and construction of the stereo amplifier mirror those of the monoblock, using the same ultra-efficient copper heat sinks with venturi cooling, the same 1% metal-film resistors, the same 69 MHz output transistors and the same fully complementary balanced configuration. The result is audio fidelity equaled by no other amplifier—except, of course, the Momentum M400 monoblock itself—and an efficient design that consumes less than 1 watt of power at standby.
The new Momentum S250 stereo amplifier receives a power upgrade, now delivering 250 Watts/channel into 8 Ohms. This is up from the original 200 Watt/channel specification. A 20% increase in transformer size, up to 1,800VA, provides the engine for this output power increase. Connected to this larger power source is a new output stage design that includes a number of major enhancements.
The driver section underwent a major revision and now features a fully complementary signal path with individual transistors employed for the positive and negative halves of the musical signal. Current drive is nearly doubled which feeds a new output stage with an open loop gain increased by the same factor of two. The sound is more spacious, delicate, and dynamic.
The distinctive power meter from the monoblock makes an encore appearance in the stereo amplifier, with a separate indicator needle for each channel. Like the monoblock, the stereo amplifier uses through-hole construction and is hand-built and individually tested in D'Agostino's Arizona facility.
The Momentum S250 employs the same chassis as the original with a small aesthetic design change to the copper feature on the faceplate sides. Additionally, the meter now displays a scale appropriate for the greater power output.
