Jensen
Twin
                        Servo 990 Mic Preamp:  
                    Transformer
                        enhanced technology for superior sonic performance.
                        Bringing science to
                        sound. 
                    
                    
                    The
                        Jensen Twin Servo 990 Mic Preamp is considered the
                        world's finest mic
                        preamp by audio experts. It's the ideal integration of
                        advanced design
                        software, hardware, engineering know-how, and carefully
                        controlled
                        'golden ears' tests. It has earned high marks for sonic
                        performance
                        since its introduction in 1988. 
                    The
                        basic circuit was originally published as an application
                        note by Jensen
                        Transformers for their finest microphone input
                        transformer, the
                        JT-16-B. Each channel uses two
                        precision 990C
                        operational amplifier modules, developed and patented by
                        Deane Jensen,
                        to achieve one tenth the distortion and twice the
                        bandwidth of a single
                        stage design.  
                    The Jensen
                        Twin Servo 990
                        mic preamp has a 19" wide
                        mainframe rack-mount chassis (1.75"H x 19"W x 8"D) and
                        can be ordered
                        with 1 to 4 channels. Additional channels can be easily
                        added later up
                        to the total capacity of the mainframe.  
                     Highlights: 
                    •
                        JT-16-B Input Transformer. Jensen's best mic input
                        model. 
                    •
                        Two
                        990 Discrete Op-Amps Per Channel. Faster, quieter, more
                        powerful and
                        better sounding than typical monolithic op-amps. 
                    •
                        Elimination Of All Coupling Capacitors From The Signal
                        Path. Results in
                        less degradation of the audio signal. 
                    •
                        JT-11-BMQ Output Transformer. Jensen's best line output
                        transformer. 
                    •
                        Input Bias Current Compensation Circuitry And DC Servo
                        Circuitry.
                        Eliminates signal degrading coupling capacitors. 
                     Standard
                          Features: 
                    •
                        Fully Sealed Conductive Plastic Gain Control. Provides
                        smooth
                        continuous gain adjustments from 16dB to 60dB. 
                    •
                        20
                        OHM MIC switch or 20dB PAD switch. 
                    •
                        POLARITY REVERSE switch. 
                    •
                        PHANTOM POWER switch. 
                    •
                        All
                        Front Panel Switches Are LED Illuminated. 
                    •
                        Gold Plated XLR Connectors for maximum reliability. 
                    •
                        Ground Lift Switch On Each Channel. Helpful for
                        eliminating ground
                        loops. 
                    •
                        VU-1 meter. Very accurate and informative 20 segment LED
                        meter, with
                        separate Peak LED, for monitoring preamp output. 
                    •
                        Toroidal Power Transformer With Additional Shielding.
                        Eliminates hum
                        problems so no external power supply is needed. 
                    •
                        Universal Power Supply. Internal switch provides six
                        primary voltage
                        choices to accommodate use anywhere in the world. 
                    •
                        Chassis Ground Isolation Switch. Helpful for eliminating
                        ground loops. 
                    •
                        Pin
                        2 Or Pin 3 High. Internal jumpers make changes in the
                        field easy. 
                         
                     
                    
                      
                        
                            | 
                         
                        
                          | Jensen Twin Servo 990
                                Standard Channel Detail | 
                         
                        
                          |   | 
                         
                        
                            | 
                         
                        
                          | Jensen Twin Servo 990
                                Back Panel Detail | 
                         
                      
                     
                     Specifications,
typical
                          (0dBu = 0.775V): 
                    
                      
                        
                          | Voltage Gain Range | 
                          +1dB | 
                          16 to 60 | 
                          dB | 
                         
                        
                          |   | 
                            | 
                            | 
                            | 
                         
                        
                          | E.I.N.,
                                20-20kHz
                                bandwidth, unweighted, 60dB gain, 0dBu
=
                                0.775V | 
                          150 Ohm source | 
                          -128.7 | 
                          dBu | 
                         
                        
                           
                               | 
                            | 
                            | 
                            | 
                         
                        
                          | Frequency Response,
                                ref: 1kHz | 
                          20Hz | 
                          -0.05 typ, -0.1 max | 
                          dB | 
                         
                        
                           
                           | 
                          20kHz | 
                          -0.05
                              typ, -0.1 max | 
                          dB | 
                         
                        
                           
                           | 
                          0.4Hz
                              and 140kHz | 
                          -3 | 
                          dB | 
                         
                        
                          |   | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          | Time
                                Domain Response | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          |      Deviation
                              From Linear Phase (maximum) | 
                          20Hz to
                              20kHz | 
                          +2 | 
                          deg | 
                         
                        
                          |      Group
                              Delay  | 
                          20Hz to
                              120kHz | 
                          2.16 +0.05
                             | 
                          µs | 
                         
                        
                          |      Squarewave
                              Risetime  | 
                           
                           | 
                          2.2 | 
                          µs | 
                         
                        
                          |      Squarewave
                              Tilt  | 
                          20Hz | 
                          5.8 | 
                          % | 
                         
                        
                          |    | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          | Total
                                Harmonic
                                Distortion (note 1) | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          |      Output
                              Level +4dBu, any gain setting | 
                          100Hz to
                              20kHz | 
                          0.001
                              typ, 0.003 max | 
                          % | 
                         
                        
                          |   | 
                          20Hz | 
                          0.036
                              typ, 0.100 max | 
                          % | 
                         
                        
                          |      Input
                              Level +8dBu (note 2) | 
                          100Hz to 20kHz | 
                          0.001
                              typ, 0.003 max | 
                          % | 
                         
                        
                          |   | 
                          20Hz | 
                          0.120
                              typ, 0.300 max | 
                          % | 
                         
                        
                          |    | 
                            | 
                            | 
                            | 
                         
                        
                          | Common Mode Rejection
                                Ratio | 
                          60Hz | 
                          125 | 
                          dB | 
                         
                        
                           
                           | 
                          1kHz | 
                          100 | 
                          dB | 
                         
                        
                           
                           | 
                          10kHz | 
                          80 | 
                          dB | 
                         
                        
                          |    | 
                            | 
                            | 
                            | 
                         
                        
                          | Common Mode Input
                                Voltage | 
                           
                           | 
                          +300 | 
                          V-pk | 
                         
                        
                          |    | 
                            | 
                            | 
                            | 
                         
                        
                          | Optimum microphone
                                Impedance (switch selectable) | 
                           
                           | 
                          150/20 | 
                          Ohms | 
                         
                        
                          |   | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          | Input
                                Impedance, +15%
                                max | 
                          20Hz to 20kHz | 
                          1.27 | 
                          k Ohms | 
                         
                        
                          |   | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          | Phantom
                                Power  | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          |      Voltage | 
                           
                           | 
                          +52 | 
                          VDC | 
                         
                        
                          |      Current
                              (maximum) | 
                           
                           | 
                          9.5 | 
                          mA | 
                         
                        
                          |   | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          | Maximum
                                Output Level | 
                          75 Ohm load | 
                          +24 | 
                          dBu | 
                         
                        
                          |   | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          | Output
                                Load Impedance
                                Range | 
                          minimum/nominal | 
                          150/600 | 
                          Ohms | 
                         
                        
                          |   | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          | Output Source Impedance | 
                          20Hz to
                              20kHz | 
                          70 +5
                             | 
                          Ohms | 
                         
                        
                          |   | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          | Power
                                Requirements, 4
                                Channels | 
                          +15% | 
                          100,
                              120, 140, 200, 220,
                              240 | 
                          VAC | 
                         
                        
                          |   | 
                           
                           | 
                          48 to 66 | 
                          Hz | 
                         
                        
                           
                           | 
                           
                           | 
                          25 | 
                          Watts | 
                         
                        
                          |   | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          | Dimensions
                              (note 3) | 
                           
                           | 
                          1.75H x
                              19W x 8D | 
                          Inches | 
                         
                        
                          |   | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          | Notes
                                :  | 
                           
                           | 
                           
                           | 
                           
                           | 
                         
                        
                          |      Unless
                              otherwise specified : 25°C ambient, 150 ohm
                              source, 600 ohm load. | 
                         
                        
                          |      (1)
                              Low frequency response distortion is almost
                              entirely 3rd harmonic. | 
                         
                        
                          |      (2)
                              Worst case of maximum possible input at minimum
                              gain with unclipped
                              output. | 
                         
                        
                          |      (3)
                              Handles extend 1" beyond the front panel. | 
                         
                        
                          |      "Twin
                              Servo" is a registered trademark of Jensen
                              Transformers,
                              Inc. | 
                         
                      
                     
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