John Hardy Jensen Twin Servo 990 2-Channel Microphone Preamp (Stepped Switch)

John Hardy

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Product Code: 2403-Ohm
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The John Hardy Jensen Twin Servo 990 2-Channel Microphone Preamp with stepped switch features a 22 Position Rotary Gain Adjustment. It's the ideal integration of advanced design software, hardware, engineering know-how, and carefully controlled 'golden ears' tests.

The Jensen Twin Servo 990 Mic Preamp is considered the world's finest mic preamp by audio experts. It is perhaps the epitome of transformer enhanced technology used to achieve superior sonic performance. Bringing science to sound. 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. This special 2-channel version of the Jensen Twin Servo 990 Mic Preamp was originally developed for Sony Classical to provide high resolution switch-selectable gain control. It uses a 22 position rotary switch with gold plated contacts, providing a gain adjustment range of 18-60dB in steps of 2dB. 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 is only available as a fixed two channel version, unlike the standard version.

John Hardy Jensen Twin Servo 990 2-Channel Microphone Preamp (Stepped Switch version) Features

Design 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:

  • 22 Position Rotary Gain Switch. Provides accurate and repeatable gain settings from 18dB to 60dB in 2dB steps.
  • 20 OHM MIC switch or 20dB PAD 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.

John Hardy Jensen Twin Servo 990 2-Channel Microphone Preamp (Stepped Switch version) Options

  • -20dB PAD: This really should be the option of choice for 95% of users. This will be very handy if you are recording potentially loud sources such as drums, guitar amps, and jet engines.
  • 20 Ohm Switch: This option is to help optimize microphones that have extremely low output impedances (such as Schoeps models that have 25 Ohm outputs) to work with the Hardy preamps. Optimally, a preamp will work best with these microphones if it sees the microphone as having a 150 Ohm output. This switch makes that so, and the sound opens up quite nicely. The Hardy M2 with the 20 Ohm Switch option is perhaps the finest choice you can make for use with these microphones. But if you don't have extremely low impedance microphones such as these, then go with the Default -20dB PAD option.

John Hardy Jensen Twin Servo 990 2-Channel Microphone Preamp Includes

  • Jensen Twin Servo 990 2-Channel Microphone Preamp
  • IEC Power Cable
  • Warranty Information

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What We Think


John Hardy's passion for quality has put his name at the top of the list of boutique designers of microphone preamplifiers, and has his creations at the top the lists for most coveted gear by professionals who are in-the-know and who desire the very best examples of design philosophy and implementation. John's friendship with the late Deane Jensen over the years (and Deane having been impressed with John's work with the M-1) resulted in John being contracted by Jensen to build the Twin Servo 990 preamp based on the packaging of the M-1. However, this particular special 2-channel version with 22-position switches was originally contracted by Sony Classical who desired the extra purity of this particular gain control design. The gain switches are so large that they take up what would be preamp slots 2 and 4 in the normal 4-channel chassis version of the Twin Servo 990. As a result, this 2-Channel Stepped Switch version of the John Hardy Jensen Twin Servo 990 could be considered to be the ultimate implementation of Deane Jensen's op-amp and transformer designs and John Hardy's commitment and passion for quality.

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