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I have a black-box circuit attached to a condenser microphone. I would like to replace this condenser microphone with another. I have output impedance data for both microphones across frequency. The microphones do not have identical impedance profiles.

How would I go about designing an impedance matching circuit to get similar performance from the new microphone when fitted? Subtle gain differences can be corrected with post-processing of recorded material.

Could connecting a microphone with different output impedance to the original potentially cause damage to the black-box/new microphone, or is this highly unlikely?

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  • \$\begingroup\$ Why are you assuming the black box is sensitive to source impedance? \$\endgroup\$ – Dave Tweed Oct 16 '12 at 13:23
  • \$\begingroup\$ I assumed that using a microphone with different output impedance to the original would change the sensitivity of the unit. I was also (perhaps unduly) concerned about potential damage to the microphone and/or black box \$\endgroup\$ – learnvst Oct 16 '12 at 13:32
  • \$\begingroup\$ Is it permanently attached or is it a separate mic? What is the black box model number? (or what does it do?) Can you post the impedance data for each mic? \$\endgroup\$ – Oli Glaser Oct 16 '12 at 15:02
  • \$\begingroup\$ The black box is a microphone preamp and D/A converter. The mic was permanently attached, but now it is desoldered and replaced with a connector allowing me to connect any mic. The phantom supply is 2.5V, which is in the operating range of the new mic. I could just plug the new mic in, but I wanted to see if mismatched impedance would be a problem. I can get the actual numbers tomorrow when I can get to my scope. I was asking preemptively :) \$\endgroup\$ – learnvst Oct 16 '12 at 15:20
  • \$\begingroup\$ I assume you mean A/D converter. \$\endgroup\$ – Dave Tweed Oct 17 '12 at 12:31
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To answer your original question, it's extremely unlikely that any microphone and any microphone preamp would damage each other. Just go ahead and try it.

It'll be easier to correct any frequency response problems that arise from mismatch issues in the digital domain than to try to do it with the low-level analog signal from the microphone.

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  • \$\begingroup\$ Decided to just hook it up. Sounds OK. \$\endgroup\$ – learnvst Oct 17 '12 at 16:08

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