S/PDIF input

From HwB

S/PDIF input circuits

The following circuits can be used to convert S/PDIF signals to TTL level signals which can be connected to any suitable output circuit or directly to digital electronics.



S/PDIF coax input circuit 1

                      10 nF        |         |
                       ||          |    |\   |        |\
S/PDIF input ------ ---||----100R-- ----| O-- --- ----| O----- TTL out
                   |   ||               |/       |    |/
                  75R                           10K
                   |                 74HCU04     |
                  ---                           ---

This circuit is part of circuit "Splitter for S/PDIF coax/optical output" by T. Giesberts from Elektor Electronics magazine July/August 1995 pages 78-79.

S/PDIF coax input circuit 2

                             ----10K-----  5V
                            |     /\
                           ---     |
                     4700 pF       |
                       ||          |    |\            |\
S/PDIF input ----------||---------- ----| O-----------| O----- TTL out
( /-500mV)             ||               |/            |/


The capacitor works as DC blocking capacitor. 10 kΩ trimpot signal raises its ground potential to the point that Hex Inverter IC1 recognizes the difference between a digital 1 and 0 input. When you firt test the circuit then first addjust 10 kΩ trimmer to the center and then adjust it so that the circuit receivers the S/PDIF signal well. If you have a voltmeter, you can adjust the trimpot to show around 2.6V at pin 1 of the IC. The inverter buffers the input and produces TTL 0-5V output signal. This circuit does not provide the 75 Ω termination resistor, so you need to add it if you have problems because of cable signal reflections. This circuit is part of Coax Digital Out to MD circuit design.

See also