Neumann.Berlin KM 84 User's Manual
Contents
1. NEUMANN BEF gt gt THE MICROPHONE COMPANY KM 84 48 Volt Phantom Powered From the very start Neumann has maintained close rela tions with the people using its products The suggestions wishes and demmands of these important customers often lead to the development of new standards and the intro duction of novel techniques One particularly important development began with a visit by Neumann staff to Oslo Norway in 1966 Norwegian State Televi sion planned to outfit a new station which would use transistor based micro phones Instead of using the German 12 Volt wire circuit system the engi neers wished to use the station s existing central 48 Volt DC system Neu m mann suggested a circuit in which the microphone could be operated with this 48 Volt supply by dividing the volt age across the two modulation pins and developing the nec essary current in reference to the cable shield This system is devised by using two matching 6 8 kOhm resistors where the positive pole of both modulation wires are fed to these resistors and recovered in the microphone Due to the high degree of balance because of the careful ly matched resistors no potential difference voltage ex ists between the modulation wires Thus the term Phan tom Power has come to be understood as a powering sys CENT HUTT ha wl LATE DEPRES S T TCC2. in this new type of pow ering and using a new connector for microphones in 1966 resulted with the KM 84 as being one of the great success stories in Neumann s history Following its introduction all microphone manufacturers began to produce or modi fy models for 48 volt phantom powering and this system has since become the world standard for condenser micro phone powering sr gg ag a
3. nA amp tem where no voltage is developed between the modula tion pins of the microphone and thus does not appear unless used with a corresponding microphone sr Fg A ee This type of powering sys tem has several advantag es one being particularly important in standard ap plications Phantom pow ering allows for the con nection of dynamic and ribbon mics without dam age All microphones with a symmetrical unground ed output can also be used with this powering scheme Even tube micro phones with their sepa rate power supplies can be connected to a Phantom supply without problems The first microphone made with this technolo gy was the Neumann KM 84 a miniature mi crophone with a near per fect cardioid characteristic due to the excellent KM 64 capsule it con tains The circuit was made quite small so that the mic could be made with a diameter of only 21mm and a length of 110 mm With phantom powering a truly minia ture microphone was now possible The KM 84 was designed with a 10 dB attenuation switch therefore allowing the microphone to be used up close with loud instruments By placing the pad at the gate of the field effect transistor FET this pre attenuation prevents the hot capsule signal from overloading the front end of the amplifier With the switch on a sound pressure level of 130 dB can pass through without distortion What began as a modest interest
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