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Old 30th July 2012, 10:07 PM   #1
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Default USB to power an amp?

Is possible to make an audio amp using power from USB? how much will be max output? :/

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Old 30th July 2012, 10:10 PM   #2
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I think that USB use 5v and max is 100mA right? its just 0.5 Watts :/
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Old 30th July 2012, 10:17 PM   #3
N Brock is offline N Brock  United States
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nope, standard is 500mA but some allow more, (USB 3.0) and some ports like on the macbook air allow less current draw.
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Old 3rd August 2012, 01:55 PM   #4
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If you use an efficient Class-D amplifier with NFB, and partner it with a switch-mode dc-dc converter that alters its output voltage in response to the envelope level of the signal, you can use the fact that speech and acoustic music has a high peak-to-mean ratio. The output power of the amp + dc-dc converter will have a much higher peak power capbability than the simple USB power source would imply. Obviously you also need a large reservoir capacitor value.

There was a company pushing this approach strongly on here last year.
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