Patent ID: 8948421
Filing Date: 2015-02-03
Classification: H04R

Abstract:
1. A ribbon microphone circuit comprising: a ribbon microphone unit including a ribbon diaphragm disposed in a magnetic gap formed by a magnet fixed to a frame; a step-up transformer boosting signals output from the ribbon microphone unit; buffer amplifier circuits connected to a secondary winding of the step-up transformer; an external power supply circuit externally supplying power for driving the buffer amplifier circuits; and a switch circuit including photo-relays having lights that are turned on while the external power source is being supplied through the external power supply circuit, and having contacts that are turned on or off depending on states of the respective lights, wherein while the external power is being supplied to the photo-relays from the external power supply circuit, the lights are turned on to supply the external power source to the buffer amplifier circuits, and signals output from the ribbon microphone unit are sent from the secondary winding of the step-up transformer through the buffer amplifier circuits, and while the external power source is being not supplied to the photo-relays from the external power supply circuit, the lights are turned off to prevent the external power source from being supplied to the buffer amplifier circuits, and the signals are sent from the secondary winding of the step-up transformer without passing through the buffer amplifier circuits.