INTEGRATED AMPLIFIER: Margules Audio U280sc

World Class Audio for over 40 years, Margules Audio has been delivering audio art to the World ! Margules Audio has developed its own technology, creating two world famous brands : Margules Audio, the high end line and the versatile, sought after audio product, Magenta.

The Margules Audio U280sc Stereo Amplifier is a Pure Class A, tube audio amplifier, with Active bias o Servo-controlled output stage, does not require any bias adjustments, at any time. High precision regulated voltage in the input and inverter tubes, active damping control, bias meter, 70W/channel, can work in triode, ultralinear, mono, or stereo modes.

The main design attribute is its great versatility, variable output impedance, independent gain control for each channel, precision metal film resistors, polypropylene capacitors, etc. 4 output tubes, can use 6550, KT99, KT88, KT100.

Class A Output Stage & Active-Servo Bias Vacuum tube power amps with Class A outputs are rare. Class A operation can cause the tubes to run quite hot and increases the chance of saturating the output transformer. Margules Audio engineered new technology and has eliminated this problem by incorporating Active Servo Bias (patent pending). The bias actively tracks in 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, or KT100 can be interchanged without modification. Active Servo Bias is implemented with semiconductors designed for the aerospace industry, assuring long, trouble-free operation.

Ultralinear / Triode & Strapped Operation:

Audiophiles have argued the merits of Ultralinear and Triode operation for 50 years. Triode operation gives lower distortion, at the price of reduced power output. Serious audiophiles have rewired Ultralinear amplifiers to convert them to triode operation. The U280sc ends this argument, by providing switched Triode / Ultralinear operation. For those times that you don't want the high power output, you can enjoy the more-refined sound of triodes, easily.

Unlike most vacuum tube amplifiers, the U280sc's outputs can be strapped, for twice the output. Start with a single amp, then add a second for increased power — or to convert to triode operation at the same power. Separate gain controls for each channel make precise balancing easy and simplify the setup of bi-amped systems.

Regulated Power Supply:

The input and driver stages incorporate classic, time-proven circuitry. The U280sc's design differs because it includes tightly regulated high voltage for these critical circuits. Good regulation reduces the loss of signal integrity that occurs when the signal itself shifts the amplifiers operating point. Each channel has separate regulators for improved imaging.

Zero Feedback:

The U280sc does not use overall negative feedback. This would normally result in a low damping factor, which is not desirable for most speakers. Margules Audio has developed the BEFS (Back Electromotive Force Sensor), which changes the amplifier's output impedance as the load requires. BEFS permits the amplifier to drive difficult speaker loads with exceptional dynamics and extended, controlled bass.

The U280sc's innovative design is complemented with precision metal-film resistors and polypropylene capacitors.

This amplifier disappears behind the music flow on listening and it offers a tactile three dimensional soundstage which is close to a “Live” performance. A rare example of musical breath and holographic sound.