Hi-Z versus Low-Z mics

[Brian Carling]

Someone was asking about using the newer low-impedance mics with older tube rigs:

With any circuit, the greatest transfer of energy occurs when the source impedance and the
load impedance are identical. The closer they are, the greater the energy transfer will be.

Vastly different impedances will cause loss of signal. Also, this loss will not be linear with
respect to frequency, and you lose "tone" as well. A mis-match will often ruin the frequency
response of the audio circuit.

Microphones are not all the same.
There are low impedance (500 ohms or so) and high impedance (10,000 to 50,000 or more
ohms) microphones.

The two are not interchangeable.

Someone can probably make a good treatise on dynamic, crystal, ceramic mics etc.

If you try to use high and low impedance mics in place of one another, there will
usually be a loss of signal. It may come out sounding muffled or very weak.

With the older rigs that have a high impedance mic input, you need a "hi-Z"
microphone. You can sometimes find a dual impedance mike, such as the
Turner Plus Three or a Shure 444D. These desk mics have a switch for
low or high impedance built into them, which is nice.

That way you can use the mic with either a newer rig or the older ones just by flipping a
switch. They also do not cost as much as a new Kenwood / Icom/ Yaesu desk mic either!!

I have two of the Turner dual impedance mics for sale at $35.00 each if anyone is interested.
I also have new E-V 602 mobile mics that are high impedance, and some good used Shure
404B mobile mics which I have to check on what impedance they are!

Brian, AF4K

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