Diode connection
A two-pole or multi-pole socket of a radio receiver at which the recovered useful signal is present, which is restored by the demodulator diode , is referred to as a diode socket or diode connection .
History and technology
The original audio signal is brought out by the demodulator diode of the intermediate frequency amplifier.
The diode socket initially functioned as an output and, in the case of corresponding devices, also as an input for an external signal source. Later the input and output functions were separated and switched. A turntable or tape recorder can also use the receiver's downstream output stage for playback in the loudspeaker.
In older tube radios, the diode connection consists of two banana sockets with a diameter of 4 mm and a distance of ~ 19 mm. The corresponding two-pin plug was called the diode plug and the cable was called the diode cable. To distinguish it from the external speaker socket that looks the same, the diode socket was later given a third connection for a flat pin in between, which is connected to ground in mono devices. The loudspeaker connection received a third round pin in the middle. The third pole also made it possible to use it in stereo equipment.
With the later change to the standard to the 3-pin, later also 5-pin DIN connectors , these were also referred to as diode sockets or diode plugs. The term was also used for transistor devices.
The input of a diode socket usually leads to the volume control . This signal level corresponds to that of the signal supplied by the diode.
When using a voltage divider, the diode output only has about 1/10 of the input level without load and supplies the microphone preamplifier in the tape recorder. The voltage divider reduces the attenuation of the demodulator diode with the cable capacitance and means a smaller time constant .
The diode connections , mostly designed as DIN connectors in Europe , were replaced by other connector systems ( cinch / RCA , jack plug 6.3 mm / 3.5 mm, mono 2-pole, stereo 3-pole) by the end of the eighties .
Diode cable and transfer cable
A transfer cable is required for a connection between two tape recorders with DIN sockets. It differs from the diode cable in the “crossed” wire routing, whereby the output of one device is placed crosswise to the input of the other.
If the recording TB device has a phono input (high level input), no crossover cable is used for transferring . The reproducing TB device has its LF signal on pin 3 (with stereo also pin 5 for the second channel). The recording device also picks up the audio signal at the phono input on pin 3 (with stereo also here pin 5 for the second channel).