Страница 1: ...2807 is a compact instrument of modular construction providing stabilized voltages for 8 K Microphone Preamplifiers and Condenser Microphones The low output impedance of its two amplifier channels en...
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Страница 3: ...TWO CHANNEL MICROPHONE POWER SUPPLY TYPE 2807 October 1971...
Страница 4: ...2 Connection of Measuring Instrumentation 11 3 3 Use of Ext Control Socket 11 3 4 Installation in Module System 12 4 DESCRIPTION 14 4 1 Amplifier Channels 1 and 2 14 4 2 Automatic Channel Selector 18...
Страница 5: ...better than 60 dB The two channels of the 2807 may either be used independently of one another or they may be automatically or remotely switched enabling the output of both channels to be monitored us...
Страница 6: ...nput 2 Fig 2 1 Front Panel of 2807 Two 7 pin sockets for connection of B K Condenser Microphones or Accelerometers via their associated preamplifiers to the inputs of channel 1 and 2 amplifiers respec...
Страница 7: ...potentiometers for adjustment of the input signals applied at sockets INPUT 1 and 2 respectively The range of attenuation is from 0 to 40 dB Five position switch with the following func tions Input 1...
Страница 8: ...plifiers are chopped at a fre quency of approximately 2 Hz by a relay operated from an internal multivibrator The chopped signal is available at the socket OUT PUT 1 The sockets OUTPUT 2 are grounded...
Страница 9: ...of the polarization voltage using an external DC digital voltmeter having a rating of at least 20 kil volt A CHASSIS GROUND socket which may be used as a DC return when measuring the polarization vol...
Страница 10: ...B 0002 3 For further information see section 3 3 Two miniature coaxial sockets which are con nected in parallel to the sockets of the same name on the front panel Depending on the setting of the FUNCT...
Страница 11: ...nel of 2807 VOLTAGE SELECTOR For selection of the correct mains voltage The selector may be turned to the correct voltage using a small coin or wide blade screwdriver when the knob in the centre of th...
Страница 12: ...tion using a small coin or wide blade screwdriver 3 1 2 Polarization Voltage The 200 Volt polarization voltage provided by the 2807 for condenser microphones is preset at the factory to within 1 Volt...
Страница 13: ...ppropriate operating mode 5 Depending on the operating mode selected connect one or both of the sockets OUTPUT 1 and OUTPUT 2 to the recording and meas uring instrumentation The effect of capacitive l...
Страница 14: ...rs DRIVE SHAFT SPEED con trol the output of the 2807 may be chopped at a frequency which permits the output of both channels to be recorded alternately using one chart length of the recording paper se...
Страница 15: ...g the case into a 19 inch rack it can be fitted with the slotted flanges GV 1037 or if a more rugged instrument is required the metal case can be fitted with the wooden case KA 0027 for protection For...
Страница 16: ...K Microphone Preamplifiers Type 2615 2618 2619 and 2627 Pin 4 see Fig 2 2 of the sockets is the respective input to the two amplifier channels of the 2807 whilst the remaining pins supply stabilized v...
Страница 17: ...re coaxial socket The output impedance of the amplifiers seen from these sockets is low approximately 13 n in series with 4 7 uF and therefore the effect of cable shunt capaci tance is small see Fig 4...
Страница 18: ...2807 for 1 harmonic distortion 5 0 5 c 0 10 Q a 15 Qj a v A IV I I I 1 a b 20 25 30 0 05 I 0 1 0 2 0 5 2 5 10 20 Frequency Hz Fig 4 4 Low frequency characteristics a 2807 alone 16 b 2807 plus 2627 Mic...
Страница 19: ...of the 2807 suffer from phase distortion This also applies to the microphone preamplifiers which may be used with the 2807 and therefore the phase characteristics of the 2807 with and without the use...
Страница 20: ...the socket is grounded the relay will switch from the output of channel 1 to the output of channel 2 To denote which amplifier channel is functioning when various operating modes are selected a secon...
Страница 21: ...orized voltage regulator circuit to ensure good stability and low yoltage ripple The filament and relay voltage supply delivers 12 6 and 6 3 Volts DC to power the internal astable multivibrator of the...
Страница 22: ...is given in Fig 5 1 In this arrangement the wall to be tested is built as a partition between two reverberant rooms one of which is termed the transmitter room and the other the receiver room By means...
Страница 23: ...ified by a 2606 Measuring Amplifier This has the advantage that the output from both channels can be recorded alternately using only one recorder and the same chart length of the recording paper see F...
Страница 24: ...ply ZR 0024 for each of its chan nels Fig 5 3 Vibration Preamplifier Type 2623 The 2623 is a small low noise unity gain preamplifier which has a field effect input stage to give it an extremely high i...
Страница 25: ...celerometer is mounted on a vibrating surface under investiga tion and a condenser microphone placed close to the sound generating area of interest The sound and vibration signals are fed separately v...
Страница 26: ...B from 2Hz to 20kHz and 60 dB at 200 kHz 15 pV over the 20Hz to 200kHz range with input to the amplifiers shunted to ground with a 750 n resistor In accordance with B K Microphone Pre amplifiers 28 V...
Страница 27: ...OL socket The EXT CONTROL socket may also be used with the Two Channel Selector of the 2305 Level Recorder This permits both channel out puts to be recorded alternately using only one recorder 100 11...
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Страница 32: ...s Accelerometer Preamplifiers Accelerometer Calibrators Vibration Meters Magnetic Transducers Capacitive Transducers Vibration Exciter Controls Vibration Programmers Vibration Signal Selectors Mini Sh...