Preamplifier Input Impedance

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Ribbon microphones need to be mated to preamplifiers with suitable input impedance. An impedance mismatch will degrade the performance of any ribbon mic.  A ribbon microphone needs to be paired with a preamplifier that has high enough input impedance that it won't load down the microphone. The lower the input impedance, the more the ribbon becomes damped, meaning that its movement is restricted. An overly damped ribbon tends to sound dull, with rolled off bass and slightly diminished highs. The output of the mic will also be reduced, requiring more preamp gain, which in turn adds more noise to the recording. In order to deliver its full frequency response, a ribbon microphone needs to see an input impedance of at least 4-5 times its output impedance. For example, if a microphone has an impedance of 300-Ohms, the preamplifier should have an input impedance of 1200 to 1500 Ohms, or greater. Don't confuse preamplifier input impedance with rated microphone impedance. Many preamps will specify what microphone impedance they are designed for, but this does not necessarily translate into the preamp's actual input impedance. If the input impedance is not specified, contact the manufacturer to find out what it is. Other Considerations

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