B&K 2627 User Manual Download

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Summary of Contents for 2627

Page 1: ...or Preamplifier with insert voltage calibration capability for 1 inch condenser microphones The extremely high input impedance ensures a flat frequency response over a wide range The Preamplifier conf...

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Page 3: ...MICROPHONE PREAMPLI Fl ER TYPE 2627 September 1971...

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Page 5: ...ttenuation 14 Distortion 14 Noise 14 2 3 Environmental Sensitivity 15 Temperature 15 Hu Jlidity 15 Vibration 15 Acoustic Sensitivity 16 Magnetic Field 16 Shock Sensitivity 16 3 INSERT VOLTAGE CALIBRAT...

Page 6: ...4 USE WITH OTHER EQUIPMENT 24 4 1 Microphones 24 4 2 Accelerometers 25 4 3 Microphone Power Supplies 25 4 4 Extension Cables 26 5 SPECIFICATIONS 27 5 1 2627 Preamplifier 27 5 2 Junction Box ZH 0007 28...

Page 7: ...upplies The input configuration of the Preamplifier is in accordance with IEC Recommendation R 237 1 2 PREAMPLIFIER REQUIREMENTS Transducers such as condenser microphones generally have a small capaci...

Page 8: ...t the transmission ratio is independent of frequency at these frequencies but depends on the total capacitive loading of the trans ducer Any capacitance additional to the transducer capacitance e g th...

Page 9: ...equency decreases The cut off frequency 3 dB point is where wRC 1 Hence the cut off frequency f 1 27TRC A lower cut off frequency could be obtained by increasing the total capacitance C However this w...

Page 10: ...de in the Preamplifier case for storage of a B K microphone cartridge in its own case see Fig 2 1 Fig 2 1 The Preamplifier Type 2627 and mahogany case The physical dimensions of the preamplifier alone...

Page 11: ...und Heating element Signal Casing to outer screen Looking at pins from outside 120 V DC Supply Heating element Fig 2 3 Pin connection of output plug The preamplifier connects directly to the PREAMP IN...

Page 12: ...ntains a high impedance input stage coupled with a field effect transistor and a low impedance output stage A heating element 180 Q resistor is built into the preamplifier This element raises the temp...

Page 13: ...the preamplifier should also be discon nected before a transducer is connected to the preamplifier The construction of the preamplifier is such that stray capacitances and leakage resistance are kept...

Page 14: ...ncy 100 r r r r r r r r VRMS 50 0 5 0 2 0 1 J _ ___ ___ __ _____ _ _ _____ _ _ _ 1 10 2 Hz 5 Frequency Fig 2 5 Limitations of the dynamic range of the preamplifier due to capacitive loading This shows...

Page 15: ...I iII Ill I I IIJ tl I lt _ Ill i I i I I fi l II I I 41 f 1 I I I I II I I 1 1 50pF isJ __ _u I I I I II I I I 1 I i II I I 1 1 I I II 1 t 4 1 II I I I I II I I i I I 1 Hm I I I I I I I II T f I I 0...

Page 16: ...um is shown in Fig 2 8 BrUel K f r BrU I Ktcar BrUel Kjmr occcoocoooooooooooooococccoooooccoooooococcooccooo BrUel Kjatr 50 25Pj iveter Ronge __ Q__dB Rectifl _ _ loww u Freq _ _ Hz Wr Sp ed _ _ rnmf...

Page 17: ...of high humidity it may be advantageous to connect the heating element 2 3 3 Vibration Fig 2 9 shows the noise output level from the preamplifier with a dummy transducer capacitance 50 pF when shaken...

Page 18: ...t I 30 v r 2_ nl lll tlf trf itt t r t l I f 1 l l 1 lA r _ t _ i _ r _ I I fll _ If _ I I I w t tt r 1 I JI H J 1 l bt a J r r I ____ _ I i 10 IV r T l L __ j_j t d i _ i t 1 _L __ _ 1 l t t j tl 1 I...

Page 19: ...ltage sensitivity of a microphone The open circuit volt age of a microphone is defined as the vol1 age at a single given frequency which appears at its terminals when the microphone is working into an...

Page 20: ...t voltage Ec can be supplied in two ways by a The internal reference oscillator of the Measuring Amplifier which can be used to give a voltage at a frequency of 1 kHz or b an external generator such a...

Page 21: ...is terminated in the same acoustical impedance Then on the Measuring Amplifier depress the push buttons Ref 50 mV RMS and Insert Volt Cal Int Then adjust the GAIN CONTROL until the voltage V is the s...

Page 22: ...the external generator to be the same as that of the sound source Depress the push button Insert Vol Cal Ext and adjust the output of the generator until the voltage V indicated is the same as before...

Page 23: ...the preamplifier and the indicating instrument Fig 3 2 shows the preamplifier connected to the junction box Fig 3 2 Junction Box ZH 0007 and the Type 2627 Preamplifier The pin guard ring on the pream...

Page 24: ...V indicated on the measuring instru ment 22 6 Switch the sound source off leaving the microphone terminated in the same acoustical impedance Switch the function selector on the Junction Box to positi...

Page 25: ...F O socket is electrically isolated from the body of the junction box 3 3 SYSTEM CALIBRATION The insert voltage technique enables any practical sound level at any frequency to be simulated and recorde...

Page 26: ...icrophones and adapters for use with the Type 2627 Preampli fier The nominal cartridge polarization is 200 V except for the Type 4148 which requires cartridge polarization of 28 V The Type 4148 may be...

Page 27: ...that given on the calibration chart The new sensitivity Sv is given by where s v Sv Sv Ct Cc Ct Cc the calibrated voltage sensitivity with cable capacitance Cc the accelerometer capacitance the new ca...

Page 28: ...see Fig 2 5 4 4 CABLES Extension cables are available to enable them icrophone and preamplifier to be operated at a remote distance from the Measuring Amplifier Analyzer or power supply The B K exten...

Page 29: ...ge Max Output Current Frequency Range with 50 pF input capacitance see Figs 2 6 and 2 7 Attenuation Preamplifier alone with 1 inch microphone Diameter 23 8 mm 0 936 in Length 99 mm 3 9 in Length with...

Page 30: ...Accessories included 5 2 JUNCTION BOX ZH 0007 Dimensions overall Weight 28 see Fig 2 5 for 1 distortion limits 15 uV so uv 3 uV Better than 60 dB attenuation at 1 kHz 120 V 2 rnA Heater 12 V 60 rnA In...

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Page 32: ...rs Accelerometer Preamplifiers Accelerometer Calibrators Vibration Meters Magnetic Transducers Capacitive Transducers Vibration Exciter Controls Vibration Programmers Vibration Signal Selectors Mini S...

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