Optical digital audio input port on MacBook Pro

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Optical digital audio input port on MacBook Pro

I believe that the optical digital audio inputs on the latest MacBook Pros are defective. I am not sure if the problem is with the hardware or the software.

I use two analog-to-digital converters in my recording studio: the Grace Design Lunatec V3, and the Mytek Stereo96 ADC. Both produce a SPDIF stereo signal with a Toslink output port. I use a Toslink cable with the required 3.5mm adapter.

Both of these converters work perfectly with my 24" iMac. In mid-December of 2009, I got a 15" MacBook Pro. There was difficulty getting the MacBook Pro to recognize a signal from either converter, and when the signal was recognized, the recordings were crackly, pitch-shifted, off-speed, and sometimes parts of the recording would get repeated. All of the settings were adjusted, including the bit-rate and sampling frequency, as well as the Audio Resolution (in both Garage Band and Twisted Wave).

I took the MacBook Pro to the Apple Store, and was very pleased with the service there. My MacBook Pro was replaced with a new one. However, when I brought the new MacBook Pro into my studio, there were the same problems.

At the encouragement of a technician at Apple Care, last weekend I brought one of my converters (the Lunatec V3) to the local Apple Store and made recordings on a number of their machines. The results:

Perfect recordings on the 27" iMac and the Mac Pro. This is in addition to my own 24" iMac.

The same problems - dropped connection, crackly noise, shifts in pitch, and repeated phrases - in two 17" MacBook Pros and one 15" MacBook Pro. This is in addition to the two 15" MacBook Pros that I have tried at home.

I have a case number with Apple Care, but haven't heard back from anyone in a week. I am thinking of just returning the MacBook Pro, but it is a very nice machine in every other way.

Is this an acknowledged problem at Apple, and can a fix be expected?

Thanks,

Mike

MaBook Pro 15" late 2009, Mac OS X (10.6.2)

Posted on Jan 16, 2010 5:48 AM

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Answer 1

Jan 17, 2010 2:59 AM in response to Desperaudio

Have you tried a different cable? The audio ports on the MBP both seem to be of a slightly different size than what seems normal. None of my cables seem to plug in as far on the MBP as other Macs.

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Answer 2

Desperaudio Author

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Jan 17, 2010 6:15 AM in response to DaddyPaycheck

I assume you mean a different adapter. The 3.5mm adapters are not all the same size? Have you used an adapter in the optical digital audio port of a MBP and had it work properly? And if so, where did you get the adapter?

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Answer 3

Desperaudio Author

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Jan 27, 2010 3:15 PM in response to DaddyPaycheck

Still no solutions. The internet seems oddly quiet on this subject. Has anyone out there used a Toslink cable to record SPDIF audio through the input ports of a recent MacBook Pro?

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Answer 4

Rod Hagen

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Jan 27, 2010 3:32 PM in response to Desperaudio

Hi Desperaudio, and welcome to the forums,

I guess that no-one who frequents this forum has run into your specific issue, but I'm wondering whether you might be better off posting your original message over in one of the sound specific "Pro Applications" groups here.

Perhaps the "Logic Studio" - http://discussions.apple.com/category.jspa?categoryID=231 or "Soundtrack Pro" - http://discussions.apple.com/forum.jspa?forumID=743 areas?

There are a lot of audio pros over there who I'd guess will have undoubtedly run into the problem if it is as ubiquitous as you indicate. I'm sure others there would be interested to know about it, too.

Cheers

Rod

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Answer 5

Jan 27, 2010 3:50 PM in response to Desperaudio

Desperaudio wrote:
Still no solutions. The internet seems oddly quiet on this subject. Has anyone out there used a Toslink cable to record SPDIF audio through the input ports of a recent MacBook Pro?

I typed 'mini toslink' into the search engine and found a couple of threads with people doing similar things as you.

E.G.: SPDIF => RCA to TOSLINK Converter => TOSLINK => MBP Input

Here's one http://discussions.apple.com/thread.jspa?threadID=2268802&tstart=0

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Answer 6

Rod Hagen

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Jan 27, 2010 4:00 PM in response to Rod Hagen

There are also a few complaints about "noisy" audio stages in MBPs in the Logic forums (though not dealing with your specific Toslink/SPDIF question. The general solution, I'm afraid, seems to be to use a firewire based audio interface instead.

Cheers

Rod

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Answer 7

Desperaudio Author

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Jan 27, 2010 4:04 PM in response to Desperaudio

It seems to me that if there is a port on a MacBook Pro called "digital audio input" then it should be possible to use it, in one way or another. By I still haven't come across a single example of it being successfully used.

It's odd, I tell ya! Odd!

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Answer 8

Rod Hagen

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Jan 27, 2010 4:14 PM in response to Desperaudio

Yes, I think its odd, too, especially given the common use of MBPs in the music game.

You say you haven't come across other examples of it being successfully used, but have you you run into other posts indicating the same problem, too?

I'm wondering if there is some specific problem involving the interaction of your own particular gear with the MBPs involved here, or whether, as DPC suggested, it may be something as simple as a cable or adaptor issue.

Is the gear you are using "common stuff" in the audio world? (hence my suggestion of trying over in the Logic forums or the like, where people will have wider experience of such things).

Good luck with it, desperaudio. Certainly sounds like a significant annoyance / pain in the proverbial!

Cheers

Rod

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Answer 9

Desperaudio Author

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Jan 27, 2010 4:57 PM in response to Rod Hagen

Thanks Rod. The MacBook Pro such a great machine in every other way, that I really, really hope to find a software solution. Although....being an audiobook narrator, the perfect machine would actually be the iPad with a toslink audio input port. Now that's a machine that would really interest me.

Message was edited by: Desperaudio

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Answer 10

Rod Hagen

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Jan 27, 2010 5:13 PM in response to Desperaudio

What a great job! I've been enjoying making very amateur "audiobooks" for a young grand-daughter recently (simply using a USB mike plugged into one of the MBPs) and emailing her mother the results. Its a great way of remembering old childhood favourites and inflicting them on (whoops, I mean 'enhancing the education of" 😉 ) the next generation. Very amateur, but she really enjoys them, I gather. Doing it for real must actually be quite a buzz.

A couple more passing thoughts on the original topic. I guess you will have worked through such things, but does it make any difference whether the MBP is running from power or from battery? The "power in" section of the MBP is located pretty close to the optical port circuitry and might contribute to interference, I guess.

Another possibility might even relate to the proximity of the Mac power adaptor or the computer itself to the other equipment. Have you tried hooking it up to different power outlets, increasing distance between the power block or the computer and the other gear, introducing some shielding, etc etc.

Finally, there can be an issue in which residual current occurs on the body of the MBP itself when it is hooked up using the "duckhead" unearthed powerplug rather than the three prong earthed power lead. I would imagine this, too, could interfere with sensitive gear. (just thoughts from an old audio buff).

Cheers

Rod

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Answer 11

Desperaudio Author

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Jan 27, 2010 5:20 PM in response to Rod Hagen

Thanks for the help, Rod. I have tried the MacBook Pros in different configurations of power and proximity. My impression is that the internal clock of the laptop is not syncing with the SPDIF clock coming into the port. It doesn't seem so much an electrical problem as a clocking problem. Especially when it can sometimes be so hard just to get the MacBook Pro to recognize a digital input. This is why I am still hopeful for a software solution.

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Answer 12

Desperaudio Author

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Jan 29, 2010 3:45 PM in response to Desperaudio

Still no answers. Why can I use a Toslink cable with the adapter (iMac) and without (Mac Pro), and get the results I need, but the same technology and setup - with adapter - will not work on a MacBook Pro?

Are there some extra controls on the MacBook Pro audio inputs that I don't know about?

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Answer 13

Rod Hagen

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Jan 29, 2010 9:17 PM in response to Desperaudio

Hi again

Well, don't know whether you are aware of it or not, but there is a "clock source" option in the "Audio-Midi Setup" utility. Could this be relevant? Lets you determine whether the Mac or the external device controls the clock speed, as I understand it.

Cheers

Rod

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Answer 14

Desperaudio Author

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Jan 30, 2010 5:07 AM in response to Rod Hagen

Hi Rod,

I have played with the Audio MIDI Setup, and the clock source remains grayed out. If I could change this setting, it might help, but it doesn't seem adjustable on my system.

Mike

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Answer 15

Rod Hagen

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Jan 30, 2010 3:18 PM in response to Desperaudio

You seem to have to create a new "aggregate device" (using the "+" button beneath the device list on the left) to be able to use it, Mike. I'm not sure how this would impact on you.

Cheers

Rod

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