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1. Col Roma Mexico D F 06700 Mexico Tel 525 514 7448 Toll free 1 888 538 8605 FAX 525 533 4654 Email info margules com mx Visit our home page in internet http www marqules com Margules U280SC zs User manual
2. Margules Audio Amplifier U280SC 25 anivesary Congratulations 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 amp 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 St
3. ereo Tube Amplifier includes a new and improved differential output as well further reducing the THD and transient distortion Ultralinear Triode amp 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 soft sound you simply switch to Triode Mode And when more power dynamics detail 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 amplifiers operating point Each channel uses separate regulators that further improve the U280 SC s already e
4. f the fuse blows again one tube is in short or damage replace it The amplifier does not sound properly Look for The proper voltages supply The amplifier output impedance selector to be in the proper position Check for further advises in the operation section of this manual Noise in your system Check for ground loops in the system No more than one physical ground should have the system Advises Always mount your amplifier in a firm platform avoiding external vibrations from loudspeakers You can change the tonal characteristics by placing your amplifier in different type of supports like footer spikes etc To minimize unwanted noise in the system Avoid excessive length in the interconnect cables Avoid having AC line cables and strong electromagnetic fields near the signal ones Because you have a servo controlled bias and the BEFS always use the best interconnects AC power line and loudspeakers cables that you can get We recommend having the gain potentiometers at maximum level In our opinion you will achieve the best sounding qualities Characteristics Frequency response 10 50KHZ Power Ultralinear 80W channel Triode 40W channel Mono Ultralinear 120W Mono triode 60W Noise 1 2M V Maximum total harmonic distortion 0 2 Weight 32KG Power consumption Standby 170W Max output 600W m MARGULES For more information please contact us at MARGULES AUDIO Uruapan 17 4
5. nger period Precaution and care This product is intended to be plugged directly to the power supply line of your house Although we have taken all the precautions to make your equipment completely safe and to comply with the safety standards we recommend to unplug it from the wall outlet if your are not going to use it for an extended period of time Keep the equipment in a well ventilated area and far away from materials that can be ignited Do not expose to rain or direct sunlight Do not open High voltage no serviceable parts inside The voltage supply should be 15 of the line nominal voltage specified in the product To clean use a soft lightly humid cloth Never take the tubes out while the amplifier is plugged It is important to substitute the tubes with the correct numbers Troubleshooting Doesn t turn on Look for Proper connection to the wall outlet The rear switch to be in on position The U280 SC has a 3 minute delay pre warm up time Wait until the current meter display reaches 35ma The circuit breaker in the rear of the amplifier is probably activated if you see the button ejected push it in One channel doesn t sound Look for The gain controls to be in the correct position The connections to be properly set A protection fuse can be blown check them and if is the case replace it Warning HIGH VOLTAGE inside Be certain to have the amplifier unplugged from the power line I
6. s from 4 to up ohms load If used as Stereo or Mono the Triode Ultralinear mode should be the same in both channels Connect the speakers to the output binding posts red to red black to black the input signal of the amplifier to the preamplifier If you are not using a preamplifier set the level controls to minimum otherwise full clockwise Check the power switch in the back of the amp to be off Connect the amplifier to the AC outlet of the wall check that all connections are OK and flip the switch to on Wait until the meter reads 43 ma The panel meter is the actual current passing through the right front output tube When overpasses the 100ma you are overdriving the tubes around 120ma coincides with the maximum power It is not important if you overdrive the tube in short periods if you do it continuously it will shorten the life expectancy of the tubes To change the tubes just unplug the A C power line cord pull out the old ones and insert the new tubes the active bias will balance them We recommend matched pair output tubes but this is not indispensable Do not substitute with other type the two 12AU7 tubes in the back of the amplifier You will unbalance the circuit and will raise the distortion Break in The break in period is about 150 hours of music reproduction Tube life expectancy For optimal performance we recommend to change the set off tubes every two years although they should last a much lo
7. xcellent 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 Zero Feedback The U280 SC does not use negative feedback as do most tube amplifiers Negative feedback results in a loss of detail and sound richness Margules has developed the BEFS Back Electromotive Force Sensor which changes the amplifier s output impedance per the load requirement BEFS permits the amplifier to drive difficult speaker loads with exceptional efficiency dynamics and extended controlled bass The U280 SC s innovative design is complemented with a fine new finish new silver coated epoxy pc boards military grade potentiometers precision metal film resistors and audio grade interstage capacitors SETUP The amplifier should be unplugged from the wall outlet Choose the proper output impedance accordingly to your speaker both channels should be the same 2 ohms from 1 to 2 ohms load 4 ohms from 4 to 8 ohms load 8 ohms from 8 up ohms load In Mono mode always use both channels of the amplifiers in ultralinear or triode mode in the same output impedance range The recommended settings are the following 2 Ohms should 4 Ohms from 2 to 4 ohms load 8 Ohm

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