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  • Radial Engineering Tonebone Twin-Servo Microphone Preamplifier - Front
  • Radial Engineering Tonebone Twin-Servo Microphone Preamplifier - Side / Open
  • Radial Engineering Tonebone Twin-Servo Microphone Preamplifier - Slant
  • Using the Twin-Servo with a condenser mic
  • Using the Twin-Servo with an active DI
  • Using the Twin-Servo with a ribbon mic

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Circuit type: Two stage variable gain all discrete using original Deane Jensen circuit with IC DC servo. Jensen transformer coupled input and output.
Frequency response: 14Hz to 85kHz / 8Hz to 100kHz (±1dB / ±3dB)
Total harmonic distortion: 0.004%
Dynamic range: 91dB
Input impedance - XLR: 1.3kΩ
Input impedance - instrument: 220kΩ, unbalanced
Output impedance: 75Ω
Maximum output: +22dBu
Mic preamp gain: +60dB
Common mode rejection (CMRR): -72dB
Equivalent input noise (EIN): -120dBu @ maximum gain
Total Harmonic Distortion (THD+N): 0.004%
Intermodulation distortion: 0.004%

Microphone input: Transformer coupled, Jensen JT-15KE
Meter: 10 segment peak indicator with hold
Polarity reverse: 180°
Pad: -15dB
Ground lift (rear panel): Lifts ground on XLR inputs
XLR configuration: AES spec: pin-1 ground, pin-2 (+), pin-3 (-)

Power: 110mA
Phantom power: 48VDC - 10mA (as supplied by 500 frame)
High pass filter: 6dB/octave @ 150Hz
Construction: 500 Series module
Size: 5.25" x 1.5" x 7" (134mm x 38mm x 178mm)
Weight: 1.75lb (0.79 kg)
Shipping size: 6.75" x 1.875" x 9" ( 171mm x 48mm x 229mm)
Shipping weight: 2.20lb (0.997 kg)
Conditions: For use in dry locations only between 5°C and 40°C
Warranty: Radial 3-year, transferable

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Radial Engineering Tonebone Twin-Servo Microphone Preamplifier

R700 0111 00
2.20 LBS
Usually ships within 24 hours.
Calculated at checkout

Product Description

Twin-Servo Microphone Preamplifier

  • Exceptionally wide frequency response from 0.5Hz to 150kHz
  • Twin-servo topology eliminates capacitors in the signal path
  • Virtually zero phase shift or bandwidth limitation
  • Oversized Jensen transformers for maximum headroom

The Radial Jensen Twin-Servo & 500 series preamplifier is an updated version of what may well be the most spectacular preamp ever made.

Originally developed by industry icon Deane Jensen in 1988, the Twin-Servo 500 is an adaptation that fits the popular 500 series format. The design begins with the legendary performance of two 100% discrete 990 op-amps cascaded in tandem to deliver 60dB of gain with less than 1/10th the distortion and twice the bandwidth of a single stage design. This maximizes the gain-margin so that no matter what the input, the lowest possible distortion will be realized. This also reduces noise at mid and low levels, a critical advantage for those that record with a wide dynamic range. In order to minimize phase distortion and retain the delicate balance of fundamentals with harmonics, all capacitors have been removed from the audio signal path and replaced by two DC servo feedback circuits. This not only reduces low-frequency noise, but also eliminates the ugly distortions associated with electrolytic capacitors that are especially degrading to low-level microphone signals when used to block phantom power in transformerless designs. To deliver the widest possible bandwidth, Jensen transformers are placed at both the input and output producing a frequency response that extends from 0.2Hz to 150kHz. The transformers further benefit with unmatched common-mode noise rejection from offending devices such as power supplies, light dimmers and motors that may be connected to the same power service.

Features include a convenient front-panel Neutrik combo connector with choice of XLR and ¼” inputs, a dual-gang potentiometer for level adjustment along with a 10 segment LED meter for signal management. This is supplemented with a 180º polarity reverse switch that toggles the absolute phase, a gentle high-pass filter to eliminate excessive resonance, a -15dB pad to prevent overload, and a 48V phantom power activation switch.

The Jensen Twin-Servo... likely the finest microphone pre-amplifier ever made.