Phonograph pickup device

Details Phonograph pickup device Phonograph pickup device

1976-09-15

1978-07-25

Phillips, Charles E.

Undertaking

274 23A, G11B 310

Patent

active

041025369

ABSTRACT:
An improved phonograph pickup device having a pivotally mounted tone arm on which a drive coil and a sense coil are mounted and are coupled to a magnetic field. The level of current flow to the drive coil alters its position relative to the magnetic field. A cueing control circuit is connected for providing feedback controlled energization of the drive coil whereby damped movement of the tone arm is provided when it moves relative to the record disc. The sense coil is connected in the control circuit to provide a feedback signal for the circuit that is proportional to the velocity of the movement of the tone arm. The device also includes a cartridge responsive to both static and dynamic forces exerted between the cartridge and the record disc. The cartridge is connected as a part of a force control circuit which also provides feedback controlled current flow through the drive coil. When the cartridge is lowered into contact with a record disc, the force control circuit portion is operative to establish a preset force level between the cartridge and the record disc and by force feedback corrects for cartridge displacement forces represented by frequencies below the audio range, such as those presented by record warpage. The output of the cartridge is proportional to the force level present between the cartridge and the record disc surface. This output is feed back to the force control circuit. This circuit also provides a reference signal which establishes the preset force level and which is applied to a phase correction network including an amplifier, the output of which establishes the level of current flow to the drive coil. A control selection circuit coupled to the force control and the cueing control circuits selects the cueing control circuit to control the energization of the drive coil in response to an up or down cueing signal and selects the force control circuit to control the energization of the drive coil when the force level between the cartridge and the record disc is at least half of the desired force level.

REFERENCES:
patent: 3623734 (1971-11-01), Toyonaka et al.
patent: 3830505 (1974-08-01), Rabinow

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