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Old 11th August 2017
Registered User
The Jensen 990 preamp was the brainchild of Deane Jensen. It made use of two transformers, two 990 op-amps and two inductive coils - hence the 'Twin" moniker. Deane believed early on that the primary cause for phase shift were the capacitors in the signal path. He also understood that noise levels are directly proportional to the input signal and desired output. To address these, he eliminated all capacitors in the signal path. He then created a two-step gain structure that can be thought of as two gears in a car - low and high - whereby at low levels, the background noise is reduced and at high gain, the circuit automatically adjusts to deliver more headroom. He then incorporated two of Jensen's finest transformers at the input and the output. The result is a stunning frequency response that ranges from around 10z to 80kHz. When we first plugged it in, we could not believe the bottom end. We thought there was an EQ patched into the signal path. We soon realized that we had never heard this type of response from any preamp before. The 990 has become legendary in that it delivers the most accurate picture of what is being presented. Unlike others that are pared down versions, the Radial 500 series Twin Servo follows Deane's original recipe with 100% discrete part placement directly on the circuit board. As a final thought, many preamps boast character... the Twin Servo boasts accuracy while delivering the warm Bessel response of the Legendary Jensen Transformer!