I am initializing a sound card using JUCE, suppose if the sound card is powered off due to various reasons, is there a way to find whether the active device is dead or alive
Generally, devices that aren't available won't show up in the list.
... Except for ASIO devices which will show up if the driver is installed, even if the device isn't physically present. The hack I use is try and start the device and, if this fails, it's probably (though not definitively) not there.