The dead OPA37-head preamplifier circuit

This circuit is a common tape recorder head amplification circuit in the 1990s. It uses the ultra-low noise precision operational amplifier OPA 37 as the head pre-op amplifier. The circuit can provide standard NAB equalization. Its voltage amplification factor is 50dB at 1kHz. The audio input signal is picked up by the magnetic head device and sent to the non-inverting input end of the OPA37. This connection method makes the op amp have a high input impedance, that is, pin 3 of the OPA37 to the ground can be approximately open circuit, and RL and CL in the circuit form the load of the magnetic head. Impedance. The value recommended by the magnetic head manufacturer should be used. The resistive and capacitive components in the circuit should use high-quality metal film resistors and organic synthetic film capacitors.

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