PURPOSE: To obtain an extremely small-sized acoustic device which requires neither a power amplifier nor a power source circuit, by providing a preamplifier for amplifying an audio signal in a housing.

CONSTITUTION: In the housing 1, an AM/FM tuner, detecting circuit 2, and the preamplifier 3 for amplifying the audio output of the circuit 2 are stored and a power source jack 4 for supplying a power voltage to them and an audio jack 5 for leading out the audio output of the preamplifier 3 are provided. A plug 8 has a power source plug 6 to be connected to the power source jack 4 and a signal plug 7 to be connected to the audio jack 5; the power source jack 6 is supplied with a DC voltage form a battery pack 9 and a signal obtained by the signal plug 7 is supplied through the battery pack 9 to an electroacoustic transducer 10 such as headphone crystal earphones.