Microsoft's spec for active PC speakers

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Hi everyone,

The next version of the AC97 audio PC specification will allow for Jack Sensing. This is a method whereby the codec automatically configures the jack connectors depending on what is inserted, be it line in, line out to active speakers, microphone, headphones etc.

Unsurprisingly, the codec works out what’s connected by measuring it’s impedance from 40Hz to 20KHz. The consequence of Microsoft’s research is that the input impedance of those lovely new active speakers you’re building should be between 4K-16K for it to be recognised!

More info here (self extracting Word doc – 1.4MB):
http://download.microsoft.com/download/whistler/WH02MS/1.0/WXP/EN-US/analog_impedance.exe

More general info here:
http://www.xbitlabs.com/articles/multimedia/display/int-sound2.html

Nice one,
David.
 
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