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sfieldhouse · Dec 13, 2006, 03:55 PM

I'm sure this has been covered elsewhere, but I can't find the right thread.

One of the things I hated about windows was the lack of being able to select the sound output, I understood that this was possible in OS X.

SO.... I have my iMac connected via the optical out (3.5mm optical) to my AV receiver. Sound is great, everything plays through my nice speakers. But thats the problem. EVERYTHING, including alerts, IM sign ins, etc... comes through six speakers.

In sound preferences the drop down box for selecting "play alerts and sound effects through..." is greyed out. Why? its greyed out on digital out.

Basically the question is : how do I get alerts and system sounds to play through my iMac's internal speakers?

The other problem is of course that the volume control on my apple remote is rendred useless, apart from in front row that is, i didnt realise that it doesnt control the itunes volume slider

hemant · Dec 14, 2006, 02:46 PM

I would also be interested to know if this is possible.

brokenbells · Dec 14, 2006, 07:29 PM

It sure is the problem this end too. Most probably - what i figure out - is that, the volume control has been blocked out for digital out, since the audio systems taking a digital in most usually have their own inbuilt amplifiers. Since the iMac comes with a 12 Watt inbuilt amplifier, the raw audo signal through the optic cable disrupts/overloads the amplifier in the AV system.

Well it is my theory, unless untill someone has a solid explanation to this.

P · Dec 15, 2006, 10:30 AM

Digital audio out is actually a bit more complicated than you'd think. The point is that it is an unmodified digital audio stream that is sent all the way to the amplifier, thereby reducing noise. Regular 2-channel audio is sent as a PCM stream - like an uncompressed digital audio file. It is not possible to control the actual volume of that file without degrading the quality (and not degrading the quality is what digital audio is all about). Instead, you control the volume at the amplifier.

5.1 channel audio is even more complicated, as then you have to send a compressed AC3 stream to the amplifier. For realtime audio (like in games) this requires something called Dolby Digital Live, DDL, a feature that is missing from most 5.1 or 7.1 "HD" audio chips on motherboards. They will only produce 5.1 audio for something that already has AC3 encoding (like a DVD) or by using the analog audio ports. Using that analog ports is much lower quality audio, however, because the signal is sent as analog between the computer and the receiver.

Anyway, about the OP: I don't have anything connected to my digital port, but I basically think that you're screwed. You can select the audio out source for USB speakers and external audio adapters, but I think that internal speakers are disabled by just inserting something into the audio out port.

sfieldhouse · Dec 16, 2006, 02:28 PM

Ive tried connecting my iMac to my amp via a USB digital audio converter, but i still couldn't select between the usb audio device and the internal speakers

not sure whats up here.

Semstudent · Dec 17, 2006, 08:58 AM

This may defeat the purpose of your use of the digital audio out, but the way I've gotten around this issue it to use an Aiport Express for the sound from iTunes. I understand that there is software (Airfoil?? or others??) that allow you to select the system audio you wish to send through your system. I find the sound quality to be exceptional using the Airport option...just my 2 cents worth.

1tuffchevy · Dec 19, 2006, 01:50 AM

I have the solution, I think, and best part is it's totally free:

Rogue Amoeba - Freebies

Download "Detour".

"Circuitous Audio
Technically speaking, Detour allows you to send audio to different output devices on an application-specific basis. What does that mean exactly? It means you can...

...send music from iTunes to your external USB speakers and keep the annoying beeps and blips of iChat going through your computer's built-in speaker.

...mute any application's sounds all together.

...change the volume of some applications relative to others. Make your email client's alerts quieter, and you'll never again be jarred from work just to receive spam. "

1tuffchevy · Dec 19, 2006, 01:53 AM

Aw crap... I think that might be PPC only. Can someone check?

1tuffchevy · Dec 19, 2006, 02:02 AM

Crap. Well, you can always try Sound Source, instead of Detour. It's a lot less powerful, but it should be allow you to route all your sound one place, and your 'system' beeps to another. Argh. This sucks. I totally think they should bring it back... at the very least, an app that outputs music to an external device, and uses the internal speakers for everything else.