| 摘要 |
PROBLEM TO BE SOLVED: To obtain a reproduced sound output with a frequency characteristic almost flat over the entire sound frequency range by reproducing low sound frequency components in the case of driving an electromagnetic coupled speaker with a digital sound signal to reproduce the sound. SOLUTION: A serial digital sound signal in n-bit is fed to a drive section 20. A speaker 10 is provided with (n+α) sets of primary coils 1, each of which connects in series with a switch circuit 24 and a constant current source 25. A low frequency correction circuit 21 enhances low frequency components of the serial digital sound signal and extends the number of bits of the signal into (n+α) bits. A serial parallel conversion circuit 22 converts the serial digital sound signal in the (n+α)-bit from the lower sound frequency correction circuit 21 into a parallel sound signal in the (n+α)-bit. A corresponding bit of the parallel sound signal in the (n+α)-bit from the serial parallel conversion circuit 22 applies ON/OFF control to any corresponding circuit in the (n+α) sets of the switch circuits 24.
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