audio board ... input and output impedances...


Would someone please tell me what the specs are for the audio output and input levels and impedances for computers....


Larry ve3fxq

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There are some variations from sound card manufacturer to another, just like in hifi equipment.

You can find some details at

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Line level outputs on consumer PC soundcards can typically output signals up to 2V levels and ouput impedance typically from tens of ohms to few hundred ohms (quite typical is 30-400 ohms). Those line level outputs are designed to be connected to consumer equipments (normal Hifi amplifier with -10dB nominal level line input) or powered multimedia speakers.

Typical line level audio input connections are generally designed to accept audio signals in the range of 500 mV to 2V. They are designed to operate nicely with consumer equipments like tape decs and CD players nicely (those devices use typically -10dB signal level). Line level audio input connectors are high impedance inputs (typically around 10-47 kohm).

Most sound mic card inputs require a minimum signal level of at least 10 millivolts. Sound Blasters and some older 8-bit cards need 100 millivolts. Practically all consumer soundcard supply bias voltage on their outputs to power the electret microphones (the only microphone type which works with this kind of cards). The input impedance of the typical PC soundcard microphone input is typically in order of 1500 to

20000 ohms (can vary from card to card).
Tomi Engdahl (
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Tomi Holger Engdahl

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