Optically connecting (pc) motherboard to receiver (7.1)

S

Skybuck Flying

Hello,

The following motherboard has an optical out:

ASRock 939A790GMH, link to manual:

http://europe.asrock.com/downloadsite/manual/939A790GMH.pdf

The following receiver has an optical in:

Denon AVR 1909, link to manual:

http://usa.denon.com/DocumentMaster/US/AVR-1909-OM-E_202A.pdf

It seems the receiver manual does not explain how to use optical connections
or what they are for... at the back of the receiver it says "tv/cbl"
something like that...

So is optical in only ment for tv signals ? or can it be used for audio
connections as well ? (I guess tv has that as well...)

Also does optical signals carry 7.1 signals ? Since the receiver has 7
speakers connected (no bass/subwoofer)

So in other words:

Is an optical cable ment for 7.1 connections as well ?

Thanks for any answers... if I could use only 1 optical cable instead of 3
or 4 electrical/rca cables that would be pretty cool and handy and more safe
electrical/light ? ;)

I guess if the receiver would get input from a tv signal it could somehow
transfer/broadcast this audio towards speakers so that's one thing... but
can it also disconcern the individual speaker signals (stereo signals) ?
Hmm...

So in other words: do these systems support carrieing 4 stereo signals
across one optical cable ?

Bye,
Skybuck.
 
P

Paul

Skybuck said:
Hello,

The following motherboard has an optical out:

ASRock 939A790GMH, link to manual:

http://europe.asrock.com/downloadsite/manual/939A790GMH.pdf

The following receiver has an optical in:

Denon AVR 1909, link to manual:

http://usa.denon.com/DocumentMaster/US/AVR-1909-OM-E_202A.pdf

It seems the receiver manual does not explain how to use optical connections
or what they are for... at the back of the receiver it says "tv/cbl"
something like that...

So is optical in only ment for tv signals ? or can it be used for audio
connections as well ? (I guess tv has that as well...)

Also does optical signals carry 7.1 signals ? Since the receiver has 7
speakers connected (no bass/subwoofer)

So in other words:

Is an optical cable ment for 7.1 connections as well ?

Thanks for any answers... if I could use only 1 optical cable instead of 3
or 4 electrical/rca cables that would be pretty cool and handy and more safe
electrical/light ? ;)

I guess if the receiver would get input from a tv signal it could somehow
transfer/broadcast this audio towards speakers so that's one thing... but
can it also disconcern the individual speaker signals (stereo signals) ?
Hmm...

So in other words: do these systems support carrieing 4 stereo signals
across one optical cable ?

Bye,
Skybuck.
Click to expand...

SPDIF is an inferior technology. You would not be happy with it,
because of how it handles channels.

In many situations, you get stereo (2 channels).

If you're playing a DVD, with AC-3 encoding available, the
AC-3 stream can be sent across the TOSLink cable to the receiver.
If the receiver has the appropriate digital decoder inside, it
reconstructs 5.1 audio.

It is generally difficult, to get a computer to encode analog
audio, convert to AC-3, maintain lip sync, and send it to the
receiver. My Nforce2 motherboard could do that, with 50 millisecond
latency, as there were separate DSP processors to do that.
Doing that with the system processor, is generally too slow
for gaming situations.

With the SPDIF, you're either looking at 2.0 configuration or
occasionally hearing a 5.1 configuration. It would be up to
your receiver, to "synthesize" additional channels, if it was
capable of doing so. The sound is just, inferior in every
possible way.

If all you wanted was a stereo signal, SPDIF is wonderful.

In general, I think placing the SPDIF connector where they
have, on your motherboard example, is a mistake. They should
have used a standard 6 jack analog configuration, for maximum
useful functions.

There have been computers, with mixed function SPDIF connectors.
Some laptops for example, have what looks like an ordinary
audio jack (1/8" stereo connector). But if you pull out the
plug and look inside the hole, you'll see the glow of a
red LED. And that LED is actually a TOSLink transmitter
for SPDIF_OUT. So it is possible to make hybrid analog/digital
jacks, for a few dollars more. You plug a TOSLink cable with
the right kind of adapter on the end, to access the red light
from the embedded TOSLink red LED transmitter.

Page 42 of the Denon manual, mentions "Digital In" mode, with
options of PCM and DTS. If left in Auto, it will detect 2.0
or 5.1 coming over TOSLink on its own. Or you can select PCM
(2.0 channel) or DTS (5.1 channel) manually. To test DTS,
use a commercial DVD movie, and on the new motherboard, select
Digital out to send the signal across the optical (TOSLink) cable.

This is an example of a TOSLink cable. It uses plastic fiber
optics internally, to make as cheap a cable as possible.

http://ep.yimg.com/ca/I/yhst-67720110273938_2156_14495974.jpg

This is a closeup of a TOSLink connector. This square thing
should fit in the back of the Denon, on the left. Red light
should come out of the hole in the middle of the metal part.

http://upload.wikimedia.org/wikipedia/commons/4/41/TOSLINK.jpg

*******

To connect up 7.1 analog, you'll need four identical cables,
each consisting of a 1/8" stereo plug on one end, and two
RCA (cinch) connectors on the other end. That's my best guess,
based on the pictures in the manual. It appears external in
is done with RCA. This particular cable costs $3, so you'll
need $12 worth of cables if you don't already have them.

http://ecx.images-amazon.com/images/I/41H+lLci4rL._SL500_AA300_.jpg

Paul
 
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