SPDIF output from computer

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Hi all

Hopefully someone might be able to shed some light on a little problem I'm

I have a brandname PC (NEC, Packard Bell...same thing) which I'm setting up
basically as an entertainment PC (ok, dont roll your eyes). It is an MSI
mainboard produced specifically for the brand and MSI website has little to
no useful info on the board.

Natrually I have no information as to the connectors on the mainboard of
this PC but have concluded that the onboard SPDIF output connector comprise
a 3 pin header GND, signal & +5V. I made an assumption that the output level
would be a standard. When connected to my amp (all sheilded / coax cable) I
do get all the right indications as to DD, DTS, PCM etc. and the audio all
comes from the correct speakers (and sounds a damn side better than using
the 6 analogue outputs from the shitty onboard amps through the 6CH input on
the amp). However I do get faint clicks & pops...certainly not normal, and
when I played back a recording I had made from my camcorder (in DD 5.1)
there was at one point an audio dropout of a couple of seconds.

I havent dragged a CRO home yet to look at the signal, but am beginning to
wonder as to whether the output is TTL instead of the typical SPDIF level.
Anyone have any ideas? Maybe TTL to be connected to a toslink module?

Thanks in advance

Re: SPDIF output from computer

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Identify the sound chip. Its datasheet will often have an application
circuit or reference design.

- Franc Zabkar
Please remove one 'i' from my address when replying by email.

Re: SPDIF output from computer

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I tested the output last night and it is indeed a TTL signal. The simplest
solution would have been to connect straight to a Toslink TX module (I
didn't have any DVD players laying around that were otherwise useless
though) and use optical but instead knocked up a crude but effective
converter to hookup to the coax input on the reciever (There are a couple of
simple circuits floating around on the web for buffering & crude impedence
matching). The thing does however work a treat.


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