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Timetheus · Dec 18, 2009, 08:30 PM

So I'm attempting to connect my 2006 MBP CD to a receiver with optical in, but I'm not getting any sound out of the set-up.

I know the optical out on hte MBP is working in the sense that I have a light at the opposite end of the optical cable, and the audio pane in preferences is set to "digital out." I also know the optical in on the receiver is working fine, as I've successfully run it from other devices. But when I connect the MBP to the receiver I get nothing whatsoever. I even tried it with a different receiver to no avail.

The two are connected via a 10ft mini-toslink to toslink cable (no adapter). I have noticed that using the optical out on my cable box results in a noticeably brighter light on the opposite end of the cable than the one visible when plugged into the MBP. Is it possible that the optical transmitter on the MBP is simply too weak to register a signal across a 10ft cable?

I may order a shorter cable and/or adapter to experiment with, but does anyone else have any suggestions?

imitchellg5 · Dec 18, 2009, 08:49 PM

What OS are you running? Oddly, when 10.6.2 came out, optical out stopped working on my MacBook Pro. I repaired permissions and it started working again... it was really weird... might be your issue here.

Timetheus · Dec 18, 2009, 10:16 PM

10.5.8, still worth a shot though. Some sort of driver issue?

imitchellg5 · Dec 20, 2009, 11:42 AM

Yeah that's what I figured. Hopefully that'll do something for you.

Timetheus · Dec 20, 2009, 10:25 PM

Well, now things are much, much worse.

Somehow over the course of trying to get the optical audio work, my MBP has decided to stop giving me audio at all. The system preference pane is permanently stuck on "internal speakers" as an output source, but I get no sound whatsoever from either the internal speakers or from any headphone plugged into the audio out. The digital light no longer comes when a the optical cable is plugged in either.

I've tried resetting the PRAM, repairing permissions, and spraying canned air into the line out to no avail. The system profiler shows audio hardware as per usual, so apparently the sound bard isn't completely shot, it's just not doing its job.

Suggestions?

AKcrab · Dec 20, 2009, 10:35 PM

Getting the left I/O board replaced shouldn't cost you too much.

Timetheus · Dec 21, 2009, 01:15 AM

Well, this just keep getting weirder and more logic defying -

Thinking it might be a software issue I took the radical (and horribly Windows like) step of reinstalling Leopard w/ and archive and install. This did nothing to fix the sound problem, however, so I was about to give up.

Fishing blindly for a solution, I happened to click the "show volume in menu bar" box, which - beyond all logic, reason, or sensibility - restored sound through the on board speakers, though not to headphones. I had literally tried everything else. I still cannot get the machine to recognize a headphone plug, but it's progress.

The fact that clicking a box in the systms prefs fixed it to an extent makes me think that it might be a software issue, but then how would reinstalling the OS not have fixed that?

imitchellg5 · Dec 21, 2009, 12:11 PM

Wow. This is the weirdest issue ever. The thing is, if you take it in, the techs probably won't have a clue either.

Timetheus · Dec 21, 2009, 11:26 PM

So I went to Bestbuy and bought a Creative X-fi USB sound card, not entirely sure it would be mac compatible (it doesn't list OS X in the requirements). It worked, so I now have usable sound through it to speakers/my 5.1 Home theater. Although AC3 decoding skips like mad through it's optical out, so I'm confined to stereo.

Probably going to have to replace the left I/O for $90 on iFixit, though I'd rather not undertake that project... Also I have no idea if that will solve my original optical output issue, though I suspect it would.

SSharon · Jan 13, 2010, 01:38 AM

This seems to be a common problem on the new unibody MBPs. My speakers work fine but my audio port no longer recognizes headphones. It turned on the optical audio, I saw a red light in the port, and eventually I got it to turn off although I don't remember how. Some reports I read on the apple boards speculate that sending audio in through the port at the wrong voltage is the culprit . . . despite the fact that the port is designed for audio input as well as output.

My MBP is still under warranty so I am thinking of having them replace it, but I was hoping to figure out exactly what happened and avoid the problem in the future.

I only noticed the problem with my headphone port when I tried plugging it into my HDTV in conjunction with an HDMI cable since of course apple doesn't have audio over HDMI (is this a display port issue or an apple software issue?).

If I learn anything new about the issue I'll be sure to report back here.

Spheric Harlot · Jan 13, 2010, 05:51 AM

Originally Posted by SSharon

Some reports I read on the apple boards speculate that sending audio in through the port at the wrong voltage is the culprit . . .

I'm trying to figure out what this means.

Do you have a link handy to a thread with this possible explanation?

SSharon · Jan 13, 2010, 10:38 PM

Originally Posted by Spheric Harlot

I'm trying to figure out what this means.

Do you have a link handy to a thread with this possible explanation?

Sorry if I wasn't clear. There seem to be a few similar issues affecting a few generations of macbook pros. I don't have a link to the exact threads I was reading, but this is a sampling.

Optical Audio Out Stuck On, MacBook Pro : Apple OS X
Internal Speaker Issue on MacBook Pro... [Archive] - Mac Forums
Apple - Support - Discussions - No sound from optical output ...