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Need help with S/PDIF splitter - Coax -> Coax + Optical

I

Itai Tavor

Jan 1, 1970
0
Hi,

I have a computer with a coax S/PDIF output, and I want to add an
optical output. The coax->optical conversion is easy
(from http://www.epanorama.net/documents/audio/spdif.html):


+----------------------------------------------- Coax
| Out
------- | +--10K--+
| | 10 nF | | -------
Comp. | ------- | || | |\ | |\ | |
S/PDIF |-----------+---||---100R--+--| O--+---+---| O---|TOTX179|--
Optical
OUT | ------- | || |/ | |/ | | Out
| 5cm 75R 10K -------
------- coax | 74HCU04 |
--- ---

But I'm usure about termination issues. First, how does the short coax
from the computer affect the termination of the output? Is the 75ohm
still needed? And with that resistor in the circuit, the termination is
messed up when a coax output cable is plugged in - how can I deal with
that?

I don't want to use a manual switch to select one of the outputs, and
I'd use an RCA socket with an integrated switch if I could find one, but
I can't.

Any advice?

TIA, Itai
 
K

Kalman Rubinson

Jan 1, 1970
0
Just like a 75ohm video splitter.

Kal
 
I

Itai Tavor

Jan 1, 1970
0
So, in this case that would mean a 75ohm resistor in series with the
Coax output?

I'm really confused about the input termination... the parallel resistor
is there to terminate the input cable... but in this case, with such a
short connection, it just terminates the compter's 75ohm output? If
that's correct, then a series resistor to the output cable would really
be all I need to add.

Thanks, Itai
 
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