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JeffTL
Nov 14, 2004, 05:06 PM
My iMac G5 (1.6 GHz 17" 1GB) is shipping by Thursday and I have a question about the sound.

I have a 2.1 set of Boston Acoustics Digital BA735 speakers that were on a Gateway computer -- these are the ones with the mini plug for connecting to a Creative sound card; I believe they are S/PDIF. I am hoping to be able to digitally connect these to the iMac -- I think it is possible, but has anyone else here tried anything like this on an iMac G5 yet?


Thanks!

mslifkin
Nov 14, 2004, 08:10 PM
If I'm not mistaken, the digital audio output on the iMac G5 is an optical (TOSLINK) output. It sounds (no pun intended) like the speakers you have connect via a mini DIN connector, so that's probably not going to work. The iMac does have built-in stereo speakers, plus it's got a headphone jack that you could plug regular stereo speakers into. If you want the 5.1 surround sound from the optical outputs there are speakers that will plug directly into the optical output, I'm just not sure which brands are available.

Regards,
Marc

Anonymous Freak
Nov 14, 2004, 09:19 PM
There are three forms of digital speaker connection:

S/P DIF (Sony/Philips Digital Interface Format) sends the digital signal over a wire. The most common physical connector type for this is an RCA jack (the kind that you see in groups of three in red/white/yellow on the back of your VCR,) and it transmits one direction only over the single wire.

TOS-link is an optical fibre link. Technically it uses the same signaling as S/P DIF, only over an optical link instead of of a copper wire. This is what the Power Mac G5 and iMac G5 have. (The iMac G5 uses a 'combo jack' that uses a mini-plug sized optical jack that doubles as an old-fashioned analog headphone jack.) TOS-link has a small laser diode in the transmitting end (so if you look in the port, you'll see a red light,) and a photoreceptor in the receiving end.

Proprietary: Any of a hundred custom digital connections used by different companies. This is what Creative Labs uses for their branded speakers. They specifically use a small multi-pin round plug for it. (Looks kind of like older Macintosh serial ports.)

Looking at references to that speaker model, it looks like it uses an S/P DIF input. Which means that it will not work with the Mac. (It appears that SOME models of that speaker ALSO have an analog input, in which case you can use them analog with the Mac, but if yours only has the digital then you're out of luck.)

JeffTL
Nov 14, 2004, 10:26 PM
Well, according to Apple, the iMac G5's port has S/PDIF (http://developer.apple.com/documentation/Hardware/Developer_Notes/Macintosh_CPUs-G5/iMacG5/03_Input-Output/chapter_4_section_15.html). The connector for my sound system looks to physically be a mono mini plug, though of course the information it is transmitting is digital stereo. Does anyone know if this is the type of connector the iMac uses?

Thanks.

Anonymous Freak
Dec 23, 2004, 03:53 PM
Well, according to Apple, the iMac G5's port has S/PDIF (http://developer.apple.com/documentation/Hardware/Developer_Notes/Macintosh_CPUs-G5/iMacG5/03_Input-Output/chapter_4_section_15.html). The connector for my sound system looks to physically be a mono mini plug, though of course the information it is transmitting is digital stereo. Does anyone know if this is the type of connector the iMac uses?

Thanks.

Yes, Apple has it written confusingly. It is technically an S/PDIF output, but over TOSlink (S/PDIF really defines the signal, not the connector, but the copper RCA connector is usually just called S/PDIF, and the optical, TOSlink.)

The physical connector on the iMac is a combo minijack/mini-TOSlink connector. It uses the same physical plug shape as a conventional headphone plug (a 1/8" minijack,) but it has a laser-LED transmitter on the end. So it will take either a conventional headphone plug for analog, or a special mini-TOSlink plug that looks similar to the minijack, only it's plastic, with a fiber-optic core in the center, for digital.

A 'normal' TOSlink plug looks like a small squareish plug (about the same size as a 1/4" 'RCA' plug, but square,) with a small round fiber-optic core at the center that juts out from the square part just a tiny bit. The port end looks significantly different than anything on analog systems. It does *NOT* look like a headphone plug, nor does it look like an RCA plug. It is a squareish recessed port, with either a flap that pushes inward, or a small plug that you manually remove, to protect the port.

You can see pictures of a couple TOSlink cables at this link (http://www.core-sound.com/toslink-cables.html). The one on the left is a TOSlink-to-TOSlink (big square to big square) cable, the one on the right is a TOSlink-mini-to-TOSlink (headphone-jack-sized to big square) cable.

If your stereo equipment doesn't have one of these funny squareish ports, it won't work with the iMac G5 (or PowerMac G5 or AirPort Express, for that matter.) If your stereo equipment's only 'digital' audio plug looks like a conventional RCA port (the kind used for video and audio on a VCR that usually comes in groups of three: Red, White, and Yellow,) then you're out of luck. (Yes, companies make RCA-to-TOSlink converters, but they're REALLY expensive.)