Radial Jensen Twin-Servo 500 Series Mic Preamp


Mic preamp, Jensen 990 opamp, dual Jensen transformers

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SKU: R700 0111


The Radial Engineering Jensen Twin-Servo 500 Series Mic Preamp is a faithful recreation of Deane Jensen’s original Twin-Servo 990 mic pre, regarded by many audio professionals as one of the finest preamps ever made.


This mic preamp has pedigree. The circuit designed by the Jensen engineering team includes two cascaded 990 op-amps to share the load and provide 60 dB of clean gain. The two servos eliminate the need for signal-degrading capacitors in the audio path and allow for less than -120 dBu of noise.

Engineered for superior sound quality, the two oversized input and output Jensen transformers are a crucial part of the design. They contribute to lowering the noise floor and freeing the signal from hum and RF interference, while producing an extended frequency response and plenty of headroom.

Augmented by a 180º polarity-reverse switch, a -15 dB pad, and a high-pass filter that eliminates excessive low-end, the Twin-Servo opens musical tone-shaping possibilities. Other features include a dual-gang potentiometer for optimal gain, a 10-segment LED meter that gives instant visual feedback for the input signal and a 48V phantom power-activation switch to power condenser microphones. The front-panel Neutrik combo connector offers the choice of XLR microphone input and standard hi-Z 1/4″ instrument input.

Re-imagined for today, this adaptation of the Jensen Twin-Servo fits the popular 500 series format.

Jensen Mic Input Transformer
The JT-16-PCJR is exceptionally quiet and linear from 5 Hz to 50 kHz with less than 0.06% distortion at 20 Hz
Jensen Dual Op-Amps
100% discrete audio signal path without any tone-shifting capacitors
Jensen Output Transformer
The JT-11-EM is linear from 2 Hz to 200 kHz with less than 0.001% distortion at 20 Hz
180° Polarity-Reverse Switch
Reverses pins 2 and 3 at the output to help phase-align microphones when two channels are in stereo use
10-Segment Meter
10-Segment Peak Indicator with Hold. Custom-designed circuit for greater VU accuracy
Dual-Gang Pot
Simultaneously controls the dual-990 op-amp topology for optimal gain at all levels
High-Pass Filter
Gentle high-pass filter may be inserted into the signal path to reduce excessive low-frequency content and control resonance
Reduces the input sensitivity by -15 dB when amplifying exceedingly high output sources
Activates the 48V phantom power supply for use with condenser microphones and active direct boxes
Combo Input
Combination balanced XLR mic input and 1/4″ instrument input is mounted on front panel for ease of use
Ground Lift Switch
Set-and-forget rear-panel ground switch lifts the pin-1 ground at the XLR input
Available when used with the Radial Workhorse, the Omniport accesses a hi-Z instrument input
Full Enclosure
100% encased steel casing reduces magnetic interference from nearby modules that may cause noise pollution
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