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Margules Audio U-280SC Power Tube Amplifier

The U280SC high end tube amplifier, with over 20 years of evolution, is positioned as a sonic reference thanks to its ability to produce a sweet, lively natural sound, full of detail, richness and precision. Its full Class A, adjustments free design, has turned it into a favorite in the demanding audiophile community for its abilities to drive a wide variety of loudspeakers. RETAIL: $5,000.

$2,999 USED

U-280sc 25th Anniversary Stereo Tube Amplifier.

The Margules U280-SC 25th Anniversary Stereo Tube Amplifier combines the superior sound of vacuum tubes with new and innovative technology. The results are clearly apparent in its quick detailed dynamics and ultra-smooth transient response. Unusual versatility and unprecedented reliability provide an exceptional performance upgrade to an already remarkable amplifier. Class-A Output Stage & Active-Servo Bias Vacuum tube power amps with class-A outputs are rare. Class-A operation causes the tubes to run quite hot, and increases the chance of saturating the output transformer. Margules has resolved this problem by incorporating an Active Servo Bias (patent pending). The bias actively tracks the input signal, permitting full class-A output, without overdriving the tubes. Active Servo Bias also sets DC bias and AC drive levels, assuring optimum electrical and sonic performance. Throughout the useful life of the output tubes, no drive or bias adjustments are ever needed. New tubes can be installed without test equipment or time-consuming setup. Active Servo Bias also makes it possible to use a variety of output tubes. The 6550, KT88, KT99, KT100, KT 120, KT150 can be interchanged without modification. Active Servo Bias is implemented with semiconductors, which are designed for the aerospace industry, assuring long, trouble-free operation.

The New U280-SC 25th Anniversary Stereo Tube Amplifier includes a new and improved differential output, as well, further reducing the THD and transient distortion. Ultralinear / Triode & Strapped Operation. Audiophiles have argued the merits of Ultralinear v Triode operation for 50 years. Triode operation provides lower distortion, at the price of reduced power output. The U280-SC resolves this predicament by providing switchable Triode / Ultralinear operation. For those listening sessions where you prefer a more refined sound, you simply switch to Triode Mode. And when more power and punch is needed, you simply switch to Ultralinear Mode. Unlike most vacuum tube amplifiers, the U280-SC's outputs can be strapped, for twice the output. Start with a single amp, then add a second U280-SC for increased power—or to convert to triode operation at the same power level. Separate gain controls for each channel make precise balancing easy. This simplifies the setup of bi-amped systems, as well. Regulated Shunt Power Supply. The input stages of the new U280-SC 25th anniversary include a special SHUNT power supply for these critical circuits. Shunt technology provides a dramatic improvement in Q damping, the key factor in regulating voltage for those stages. Good regulation reduces the loss of signal integrity that occurs when the signal itself shifts the amplifier’s operating point.

Each channel uses separate regulators that further improve the U280-SC’s already excellent imaging. Damping is critical to overall performance including smoother transient response and overall staging. Further improvements in quickness, dynamics and the overall life-like listening experience result. Our new Power Supply is virtually indestructible due to specially designed regulation technology that protects the amp from major tube failures.


Power Ultralinear: 75w/canal
Power mono Ultralinear: 135 w
Triode: 40 w/channel
Power mono triode: 80 w
Disortion: > 0.1%
Frequency response: 20-55 khz
Signal to noise radio: > 88 db
Max power consumption: 585w
Weight: 32 kg
Mesurements in cm. W 45 H 22 D 35