[. . . ] High Frequency Circuit The capsule 01a RF-condenser microphone presents, contrary to low Irequency circuits, a low impedance output. [. . . ] : To prevent ground loops, pin 2 (circuit ground) is not connected with the , housing 01the power supply respectively the microphone. Connection to Amplifiers with Powering Facilities 11 appropriate voltage source is available in the amplilier the condenser an microphone can be powered directly. It should be so stabilised and liltered, that the unweighted noise voltage is< 10 ftV at 8 mA current consumption (Fig. Short Description These microphones are especially designed pressure transducers lor instrumentation purposes. Only the operating principle 01RF-condenser microphones allows a Irequency response to extend down to 0 Hz. Input Sensitivity and Input Impedance' Sennheiser special condenser microphones can be connected directly to all amplifiers whose input impedance is > 2 kQ. [. . . ] Sy this means the large signal on the microphone cable is maintained up to just belore the amplilier, wh ich helps to increase the signal to noise ratio. [. . . ]