Microphone preamplifiers

Microphone Preamplifiers by Brüel & Kjær are robust and acoustically optimized for a wide range of environmental operating conditions. The high‐output current capability of our preamplifiers is able to drive extremely long cables without signal degradation - even when measuring high sound pressure levels present at high frequencies. The Brüel & Kjær CCLD and classical preamplifier designs fit our range of 1/2" and 1/4" microphone cartridges.

Preamplifier Selection
  • Type 1706

    1706型

    高温対応CCLDマイクロホンプリアンプ

    定電流駆動(CCLD)入力モジュールに接続して、最高125ºCにおいて音響計測を行うことができるように設計されています。

    • Optimised for : CCLD
    • Connector at preamplifier : BNC
    • Polarization voltage support : No
    • Frequency range : <minmax min="20" max="50000" />
    • Attenuation : -0.35
  • 1711 - ½-inch CCLD microphone preamplifier

    TYPE 1711

    Short, ½-inch CCLD microphone preamplifier

    Enables you to make acoustical measurements in confined spaces.

    • Optimised for : Measuring in confined space
    • Connector at preamplifier : SMB
    • Polarization voltage support :
    • Frequency range : 20 to 20000
    • Attenuation : 0.2 dB (typical)
  • ½-inch microphone preamplifier

    TYPE 2669-B

    1/2-inch microphone preamplifier, tapered

    Preamplifier Type 2669-B is designed to operate over a wide range of temperatures, humidity, and other environmental conditions.

    • Optimised for : Acoustical
    • Connector at preamplifier : LEMO 0B, 7-pin
    • Polarization voltage support : Yes
    • Frequency range : 3 to 200000
    • Attenuation : < 0.35
  • ½-inch microphone preamplifier

    TYPE 2669-C

    ½-inch microphone preamplifier - cylindrical, LEMO 1B connector

    Microphone preamplifier designed to operate over a wide range of temperature, humidity and other environmental conditions. This microphone preamplifier is supplied without a cable.

    • Optimised for : Cylindrical
    • Connector at preamplifier : LEMO 1B, 7-pin
    • Polarization voltage support : Yes
    • Frequency range : 3 to 200000
    • Attenuation : < 0.35
  • ½-inch microphone preamplifier

    TYPE 2669-L

    ½-inch microphone preamplifier, tapered, incl. cable, 7-pin LEMO connector

    This ½" microphone preamplifier operates over a wide range of temperature, humidity and other environmental conditions.

    • Optimised for : Acoustical
    • Connector at preamplifier : LEMO 0B, 7-pin
    • Polarization voltage support : Yes
    • Frequency range : 3 to 200000
    • Attenuation : < 0.35
  • ¼-inch microphone preamplifier

    TYPE 2670

    1/4‐inch Microphone Preamplifier Type 2670

    Microphone Preamplifier Type 2670 is designed to operate over a wide range of temperature, humidity and other environmental conditions. Delivered with an integral 2M cable with 7-pin LEMO plug.

    • Optimised for : Phase
    • Connector at preamplifier : Fixed (2 m)
    • Polarization voltage support : Yes
    • Frequency range : 15 to 200000
    • Attenuation : <0.4
  • ¼-inch microphone preamplifier

    TYPE 2670-WB-1419

    ¼-inch microphone preamplifier, integral 2m cable with 7-pin LEMO plug

    Designed to operate over a wide range of temperature, humidity and other environmental conditions. Optimised for airbag measurements.

    • Optimised for : Airbag
    • Connector at preamplifier : Fixed (2 m)
    • Polarization voltage support : Yes
    • Frequency range : 1 to 100000
    • Attenuation : 11
  • CCLD microphone preamplifier for 1/2-inch prepolarized microphones

    TYPE 2671

    CCLD preamplifier for 1/2" microphones

    Microphone preamplifier designed for use with 1/2" microphones in a wide range of environmental conditions and in narrow spaces. 

    • Optimised for : CCLD
    • Connector at preamplifier : BNC
    • Polarization voltage support :
    • Frequency range : 20-50000
    • Attenuation : <0.35
  • ½-inch microphone preamplifier with insert voltage facility

    TYPE 2673

    ½-inch microphone preamplifier with insert voltage facility

    Designed to allow calibration of ½" and 1" condenser microphones by the insert voltage technique

    • Optimised for :
    • Connector at preamplifier : LEMO 0B, 7-pin
    • Polarization voltage support : Yes
    • Frequency range : 3 to 200000
    • Attenuation : < 0.05
  • ½-inch short CCLD preamplifier

    TYPE 2695

    ½-inch short CCLD preamplifier

    Designed for acoustical measurements with a CCLD input module. Prepolarized microphones can be connected to the preamplifier.

    • Optimised for : Short CCLD
    • Connector at preamplifier : 10 – 32 UNF
    • Polarization voltage support :
    • Frequency range : 20 to 50000
    • Attenuation : < 0.2
  • A-weighted Microphone Preamplifier - Type 2699

    TYPE 2699

    CCLD, A-weighted microphone preamplifier

    Designed to eliminate low-frequency disturbance caused by body boom and road noise during in-car measurements

    • Optimised for : A-weighted CCLD
    • Connector at preamplifier : BNC
    • Polarization voltage support :
    • Frequency range : A-weighted
    • Attenuation : < 0.3
Microphone Preamplifier



TABLE OF CONTENTS

1. Preamplifiers for condenser microphones
2. Classical Preamplifiers
3. CCLD Preamplifiers
4. Selecting a Preamplifier
5. Preamplifier Types

 


PREAMPLIFIERS FOR CONDENSER MICROPHONES

A condenser microphone must be combined with a preamplifier to provide impedance conversion, some filtering, and the capability to drive relatively long cables without significant signal degradation.

Our preamplifiers are designed in accordance with two principles, referred to as Classical Preamplifiers, and CCLD Preamplifiers. Each provide their own special set of features:

CLASSICAL PREAMPLIFIERS

The classical preamplifier has an easy to understand concept. It is basically a unity gain amplifier with extremely high input impedance and very low input capacitance. 

  • The supply voltage can be either ±15 V DC or a single 80 V DC.
  • The output signal has its own separate wire, as do the polarization and CIC voltage.
  • Pin 5 is often used for transmission of TEDS data (so called Class II TEDS).
  • Charge Injection Calibration (CIC) is performed by injecting a signal on pin 1 of the LEMO connector.

CCLD Preamplifiers

Despite its origin in the vibration transducer world, the Constant Current Line Drive (CCLD) principle is increasing in popularity in the area of sound and measurement applications. Different manufacturers market transducers using the CCLD principle under different names.

The benefit of CCLD is that the same wire is used for both the signal and the supply current. Using TEDS Class I even the TEDS data can be transmitted over that same wire (using a level controlled electronic switch as shown in the figure below). 

 


 

Classical vs. CCLD Preamplifier



Classical CCLD
Output Voltage 55 Vp 7 Vp
Output Current 2 to 20 mA 3 to 20 mA
Noise <2 µV 4 µV
Distortion ≤ 80 dB ≤ 70 dB
Verification CIC/IVC No
IEEE 1451.4 Yes Yes
Cable Price Higher Lower
Connector LEMO BNC
Microphone Type Both Prepolarized only
Accelerometer Conditioning No Yes


SELECTING A MICROPHONE PREAMPLIFIER

Brüel & Kjær offer a large selection of robust and acoustically optimised preamplifiers that allow operation in a wide range of environmental conditions. The high output current capability of Brüel & Kjær preamplifiers allows the use of extremely long cables, even with high sound pressure levels present at high frequencies.

  • Preamplifiers are available in 1/2-inch and 1/4-inch dimensions, directly fittting with the most used cartridge sizes.
  • Adaptors are available for 1-inch and 1/8-inch microphone cartridges
  • The most popular classical 1/2-inch preamplifier is Type 2669. Available in several different versions.
  • Type 2669 combines a CCLD preamplifier and an A-weighting filter in a single unit. The preamplifier is easily distinguished due to the two engraved rings
  • When insert voltage calibration is required, Type 2673 is the obvious choice.
  • Type 2695, maybe due to its small size, (half the length of the extremely popular CCLD preamplifier Type 2671), is an often overlooked unit

A CCLD input can be connected to both microphones and vibration sensors (and many other sensors with CCLD output). Due to the working principle the signal is superimposed on a DC voltage. This DC bias voltage is typically around 12 V. Bias drift (over temperature or time) will reduce the dynamic range.

Due to the lower DC supply voltage (typically 20 – 28 V DC compliance voltage out of the front-end), there is some limitation in the upper limit for a CCLD solution. Another limitation of CCLD solution is that only prepolarized microphones can be used and that CIC is not available.

This, however, in many practical applications is happily accepted to reap the benefits of CCLD: Ease of use and cheap cables!
 

PREAMPLIFIER TYPES AND APPLICATIONS 

    ½-inch microphone preamplifier ½-inch microphone preamplifier ½-inch microphone preamplifier ¼-inch microphone preamplifier Type 1706
Type No.   2669-B 2669-L 2669-C 2670 1706
Diameter inch 1/2 1/2 1/2 1/4 1/2
Optimized   Acoustical* Acoustical Cylindrical Phase CCLD
Connector at Preamplifier   LEMO 0B, 7‐pin LEMO 0B, 7‐pin LEMO 1B, 7‐pin Fixed (2 m) BNC
Connector at Instrument/Cable   B&K, 7‐pin LEMO 1B, 7‐pin None LEMO 1B, 7‐pin N/A
Calibration Facility   CIC CIC CIC CIC None
Polarization Voltage Support   Yes Yes Yes Yes No
Supply Voltage V ±14 to ±60
or 28 to 120
±14 to ±60
or 28 to 120
±14 to ±60
or 28 to 120
±14 to ±60
or 28 to 120
28
Max. Output Voltage (Peak) V 55
(5 below supply)
55
(5 below supply)
55
(5 below supply)
55
(5 below supply)
7
Max. Output Current (Peak) mA 20 20 20 20 19
Frequency Range Hz 3 to 200000
±0.5 dB
(15 pF)
3 to 200000
±0.5 dB
(15 pF)
3 to 200000
±0.5 dB
(15 pF)
15 to 200000
±0.5 dB
(6.2 pF)
20 to 50000
±2 dB (12 pF)
Attenuation dB <0.35 <0.35 <0.35 <0.4 <0.35
Noise A‐weighted, typical µV 1.9 1.9 1.9 4 4
Noise 22.4 Hz to 300 kHz, typical µV 8.2 8.2 8.2 14 15
Input Impedance GΩ || pF 15 || 0.3 15 || 0.3 15 || 0.3 15 || 0.25 6 || 0.5
TEDS UTID   1025 from
serial number
2221155
1025 from
serial number
2221155
1025 from
serial number
2221155
1025 from
serial number
2248944
1025 from
serial number
2264319
* Acoustical means a tapered preamplifier house. Other preamplifiers have cylindrical houses

 

    ¼-inch microphone preamplifier CCLD microphone preamplifier for 1/2-inch prepolarized microphones ½-inch microphone preamplifier with insert voltage facility ½-inch short CCLD preamplifier A-weighted Microphone Preamplifier - Type 2699
Type No.   2670-WB-1419 2671 2673 2695 2699
Diameter inch 1/4 1/2 1/2 1/2 1/2
Optimized   Airbag CCLD Calibration Short CCLD CCLD
Connector at Preamplifier   Fixed (2 m) cable BNC LEMO 0B, 7‐pin 10–32 UNF BNC
Connector at Instrument/Cable   LEMO 1B, 7‐pin N/A LEMO 1B, 7‐pin N/A N/A
Calibration Facility   None None IVC 10–32 UNF BNC
Polarization Voltage Support   Yes No Yes No No
Supply Voltage V ±14 to ±60
or 28 to 120
28 ±14 to ±60
or 28 to 120
28 28
Max. Output Voltage (Peak) V 55
(10 below supply)
7 55
(10 V below supply)
7 7
Max. Output Current (Peak) mA 20 19 19 19 18
Frequency Range Hz 1 to 100000
±1 dB (6.2 pF)
20 to 50000
±2 dB (12 pF)
3 to 200000
±0.5 dB (20 pF)
20 to 50000
±2 dB (15 pF)
A‐weighted to
IEC 61672 Class 1
Attenuation dB 11 <0.35 <0.05 <0.2 0, ±0.3 dB at
1 kHz
Noise A‐weighted, typical µV 4 4 1.8 4 8 Max., LIN
Noise 22.4 Hz to 300 kHz, typical µV 14 15 11 12 N/A
Input Impedance GΩ || pF 15 || 15 1.5 || 0.4 1 || 0.05 1.7 || 0.4 10
+20 to 40% || 0.5
TEDS UTID   1025 from serial
number 2264319
1025 from serial
number 2264319
No 1025 1025

WANT TO KNOW MORE?

For further details of the range, availability, and price, please use the link below to get in touch with your local Brüel & Kjær representative.