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The Margules Audio U-280SC Black Special Edition 25th Anniversary is a Class A vacuum tube amplifier designed for audiophiles seeking flexibility and high fidelity. It features switchable triode and ultralinear operation modes, allowing users to tailor the sound from smooth and organic to punchy and dynamic. The amplifier uses an Active Servo Bias system that continuously adjusts bias based on the input signal, enabling full Class A operation without manual adjustments and extending tube life. It supports various output tubes including 6550, KT88, KT90, KT100, KT120, and KT150 without modification. The U-280SC has zero negative feedback, compensated by the proprietary Back Electromotive Force Sensor (BEFS) system, which dynamically adjusts output impedance to improve damping and bass control. It includes individual volume controls per channel for precise balance and can be configured as stereo or monoblock. The amplifier has a regulated shunt power supply for low distortion and excellent imaging. Its robust build includes silver-coated PC boards, metal film resistors, and polypropylene capacitors. Dimensions are approximately 17.7" W x 8.7" H x 13.8" D, weighing about 68 lbs. It accepts unbalanced RCA inputs and has speaker binding posts outputs. The amplifier can operate without a preamplifier due to its input attenuators. The 25th Anniversary edition is noted for its refined soundstage, dynamic bass, and versatility in tube and impedance configurations.
Amplification power output and characteristics
Analog signal output specifications
Input and output connections
Size, weight, and appearance
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The closest alternatives on specs, description and the systems they turn up in, with the specs they share set side by side.
The U-280SC's power @ 8ω is 50W against the U-280SC Black 25th Anniversary's 55W and its high-frequency extension 45 kHz against 40 kHz. Both share low-frequency extension (20 Hz) and thd (0.080%).
The MB3045's power @ 8ω is 60W against the U-280SC Black 25th Anniversary's 55W, its low-frequency extension 10 Hz against 20 Hz, and its thd 0.200% against 0.080%. Both share high-frequency extension (40 kHz).
The Spirit's power @ 8ω is 65W against the U-280SC Black 25th Anniversary's 55W, its low-frequency extension 12 Hz against 20 Hz, and its high-frequency extension 60 kHz against 40 kHz. Both share class (A).
The LM-508IA's power @ 8ω is 48W against the U-280SC Black 25th Anniversary's 55W, its thd 1.000% against 0.080%, and its weight 41 kg (90 lbs) against 31 kg (68 lbs). Both share class (A).
Cary Audio Design CAD-120S MkII
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