No, a device that is designed to run on 9V AC power should not be powered with 12V AC. The voltage rating specified for a device indicates the acceptable range of voltage that it can safely handle. Applying a higher voltage than what the device is designed for can potentially damage or even destroy the device.
In the case of a device that requires 9V AC, it is important to provide it with the correct voltage to ensure proper operation and prevent any electrical issues. Using a higher voltage like 12V AC can lead to excessive heat generation, component failure, or other electrical malfunctions.
If you need to power a device that requires 9V AC and only have a 12V AC power source available, it is recommended to use a voltage regulator or a transformer to step down the voltage to the appropriate level. This will ensure that the device receives the correct voltage it requires for safe and proper functioning.