A diagnostic circuit is used for detecting the load status of an audio amplifier. The audio amplifier includes two output terminals for connection to a speaker. The diagnostic circuit may include a first circuit, which configured to generate a first signal indicating whether a signal provided via the two output terminals comprises an audio signal. A second circuit can be configured to detect a first measurement signal being indicative for the output current provided via the two output terminals, and to compare the first measurement signal with at least one threshold in order to generate a second signal indicating whether the output current has a low current amplitude profile or a high current amplitude profile. A third circuit can be configured to generate a diagnostic signal as a function of the first and the second signal.