Electronic circuit of tape record

Abstract

Abstract PURPOSE:To improve the S/N of a cassette deck by connecting a bias trap circuit across a coil for erasure head, giving an AC current sufficient for the saturation of the head to a coil of the head, converging said AC current into 0 causing the head to be demagnetized thereby reducing remarkably an output impedance of a sound recording amplifier. CONSTITUTION:A constanct current circuit 1 is a current feedback type common emitter amplifier taking a dummy coil 4 as a load. Further, an impedance converting circuit 9 has an emitter follower circuit 13 in place of an operational amplifier. The bias trap circuit 15 is connected in parallel with the coil of the erasure head 14. The circuit 15 is constituted of a 3mH coil and a 1,000 pF capacitor. A signal current is applied to a sound recording head 11 (head in common use for sound recording or sound recording/reproduction) via the constant current circuit 1 and a buffer amplifier 9. A 50 or 60Hz commercial frequency is aplied to the head 11 from a terminal 18 and the impressed voltage is reduced gradually by adjusting a variable resistor. As a result, the head 11 is demagnetized.

Inventors

• 👤 Shoichi Tanaka
• 👤 正一 田中

Bibliographic Details