I need help on electronics stuff.. Can I use 12VAC adapter for 9V device?

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I have a set of computer speakers. My brother lost the adapter and I would like to use the speakers. The back of the speaker says 9V AC in. I found two adapters in my room: Adapter A says: AC/DC Adaptor Input: AC100-240V, 60/50Hz Output: DC 4.5V, 600mA Adapter B: AC Adaptor Input: 220VAC, 50Hz Output: 12VAC, 800mA Can I use one of these for the 9V AC in speaker?