An apparatus reproduces an information signal modulating a carrier signal recorded on a magnetic tape. A portion of the signal being boosted in accordance with a characteristic of the information signal. The apparatus comprises a playback device for reproducing the information signal from the magnetic tape, a detector for detecting the levels of the portion of the signal and the rest of the signal respectively and comparing the levels with each other, and a judging circuit for judging the characteristics of the signal in accordance with the output of the detector.