DeVerm;349853 Wrote: > The schematic in that link shows a S/PDIF transmitter on both coax and > toslink. The coax output has a transformer and guess what: the BNC > connector (or RCA) is -not- connected to ground, just like I tried to > explain why they should have done that on a DAC's input when they use > the transformer anyway. > > cheers, > Nick. As I understand the convention, one is supposed to "float" the sending end of the S/PDIF coax and ground the receiving end. So a ground on the primary of the S/PDIF input transformer would be "right", by this convention. Maybe that seems to defeat the purpose of the transformer, which is to BRE.AK the ground path (galvanic isolation). However, often in better audio designs the audio signal grounds are not directly connected to the case (protective ground). Instead there is a low value resistor (I often use 4.7 ohms) between the case (to which the grounding conductor of the power cord MUST be directly connected) and the audio ground. This causes the grounding currents (mostly caused by stray capacitance) to build up most across the low value resistor, whose value is high compared to the resistance of the inter-unit cables, rather than acress the resistance of the cables themselves.
Were I designing an S/PDIF input, I might be inclined to use a pulse transformer with the primary grounded to the case through w separate low-value resistor, while the secondary was grounded directly to the circuit (audio) ground, which was in tturn grounded through a low-value resistor. -- Timothy Stockman ------------------------------------------------------------------------ Timothy Stockman's Profile: http://forums.slimdevices.com/member.php?userid=8867 View this thread: http://forums.slimdevices.com/showthread.php?t=53345 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
