. Elements of acoustical engineering. Electro-acoustics; Sound. ^TJOT^ EQUIVALENT CIRCUIT / 'â â â ^^ -' ,â ' ~^ N / \ CRYSTAL NEEDLE ''IcCmcI'mc CROSS-SECTIONAL VIEW "" '"" FREQUENCY Fig. Cross-sectional view and equivalent circuit of the mechanical system of a crystal pickup. In the equivalent circuit: Zmr the mechanical impedance of the record. Cmo the compliance of the needle. m\ the mass of the needle holder. Cm\ the compliance of the shaft. Cuirui and CmzTmi the compliances and mechanical resistances of the crystal sup- ports, mc-, Cmc and tmc the mass, complian
. Elements of acoustical engineering. Electro-acoustics; Sound. ^TJOT^ EQUIVALENT CIRCUIT / 'â â â ^^ -' ,â ' ~^ N / \ CRYSTAL NEEDLE ''IcCmcI'mc CROSS-SECTIONAL VIEW "" '"" FREQUENCY Fig. Cross-sectional view and equivalent circuit of the mechanical system of a crystal pickup. In the equivalent circuit: Zmr the mechanical impedance of the record. Cmo the compliance of the needle. m\ the mass of the needle holder. Cm\ the compliance of the shaft. Cuirui and CmzTmi the compliances and mechanical resistances of the crystal sup- ports, mc-, Cmc and tmc the mass, compliance and mechanical resistance of the crystal. m^ the mass of the pickup and tone arm. Ju the force generated by a constant velocity generator. The graph shows the voltage response characteristics with the record charac- teristic of Fig. A. Open circuit response characteristic. B. Response characteristic with 500,000 ohms shunting the crystal. 2. Magnetic Pickup.âA magnetic pickup ^'^ is a phonograph pickup whose electrical output is generated in a coil or conductor in a magnetic field or circuit. A typical magnetic pickup is shown in Fig. The. Cm2 EQUIVALENT CIRCUIT 20 .^ B ._ ~\ . - -y u Sio o 0. y /â , hy / 1 ul / -A 1000 FREQUENCY Fig. Magnetic pickup and the equivalent circuit of the mechanical system. Intheequiv- alent circuit: Zmr the mechanical impedance of the record. Cmo the compHance of the needle, mi the mass of the needle holder and armature. Cmi the compliance of the needle holder pivot. Cm2 and rui the compHance and mechanical resistance of the damping ma- terial. OT2 the mass of the pickup and tone arm. /m the force generated by a constant ve- locity generator. The graph shows the voltage response frequency characteristics. A. Re- sponse with the record characteristic of Fig. B. Equalized response characteristic. 8 Kellogg, E. W., Jour. A. I. E. E., Vol. 46, No. 10, p. 1041, 1927. ^Hasbrouck, H. J., Proc. I. R. E., Vol. 27, No. 3, p.
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