Valve Detector Receiver

The valve detector receiver is the logical extension of the crystal detector. This circuit can achieve astonishingly good selectivity, since the rectifier circuit is designed to have very high impedance. The valve detector receiver can be connected to an active PC speaker or a crystal earphone, for example, and it generates genuine ‘valve sound’.The EAA91 is a dual diode with a 6 V / 300 mA filament. In contrast to a semiconductor diode made of germanium or silicon, it does not require a minimum voltage (threshold voltage) to arrive at the knee of its characteristic curve.