Patent ID: 8090121

Claim:
An audio adapter comprising: a first audio interface having a left ear audio pin, a right ear audio pin, and a ground pin, wherein the first audio interface is an analog audio interface, the left ear audio pin and the right ear audio pin correspond to two sound channels of a stereo sound system; a second audio interface having a power pin, a left ear audio pin, a right ear audio pin, and a ground pin, wherein the second audio interface is a universal serial bus (USB) audio interface, the left ear audio pin and the right ear audio pin correspond to the two sound channels of the stereo sound system; a first amplifier having an inverting terminal, a non-inverting terminal, and an output terminal, the power pin of the second audio interface connected to the non-inverting terminal of the first amplifier, the left ear audio pin of the second audio interface connected to the inverting terminal of the first amplifier via a first current-limiting resistor, a first variable resistor connected between the inverting terminal and the output terminal of the first amplifier, the output terminal of the first amplifier connected to the left ear audio interface of the first audio interface and connected to the ground pin of the first audio interface via a first voltage-limiting resistor; and a second amplifier having an inverting terminal, a non-inverting terminal, and an output terminal, the power pin of the second audio interface connected to the non-inverting terminal of the second amplifier, the right ear audio pin of the second audio interface connected to the inverting terminal of the second amplifier via a second current-limiting resistor, a second variable resistor connected between the inverting terminal and the output terminal of the second amplifier, the output terminal of the second amplifier connected to the right ear audio interface of the first audio interface and connected to the ground pin of the first audio interface via a second voltage-limiting resistor.