Dynamic microphones work without a USB preamp?

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Level 1

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Dynamic microphones work without a USB preamp?

If I were to buy a cable that runs from my XLR Audio-Technica PRO4L dynamic microphone, with an end that fits into the Mac's 1/8" mic jack, would I get any signal? Or do I need to buy a USB preamp if I want any sound?

I only ask because from my understanding an iMac's mic jack requires that any microphone plugged into the mic jack must power itself, and I'm not sure if a dynamic microphone meets that requirement.

17" iMac, 2.16gHZ, Mac OS X (10.4.10)

Posted on Aug 8, 2008 8:30 AM

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Answer 1

Duane

Level 10

124,293 points

Aug 8, 2008 8:47 AM in response to Gafaddict

The audio input on the iMac is a "line level" input. It is similar to a "tape in" or "AUX in" jack on a stereo. Therefore it is expecting a signal much larger than the signal created by a normal microphone. Therefore connecting a normal microphone to the iMac's audio input results in extremely low or no sound.

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Answer 2

The Looby

Level 4

1,285 points

Aug 8, 2008 9:53 AM in response to Gafaddict

iMac audio inputs have adjustable gain, so they're not quite the same as an ordinary
"line" input. However they don't have nearly enough gain for high-quality mics such
as the PRO 4L.

At normal conversational sound pressure levels (~ 0.01 Pa), the 4L's output would be
in the neighborhood of 10 microvolts -- while your iMac's maximum input sensitivity
is about 75 millivolts (full-scale). Not even close! That mic requires a preamp.

[iMac Audio Developer Note|http://developer.apple.com/documentation/Hardware/Conceptual/HWTech Audio/Articles/Audio_implementation.html#//apple_ref/doc/uid/TP40003978-SW281200331167]

[Audio-Technica PRO 4L specs|http://www.audio-technica.com/cms/resource library/files/967a0d8e032bf6b6/pro4lprodpro.pdf]

...have you hugged an engineer, today?

Looby

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