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

19 replies

Desperaudio Author

Level 1

0 points

Jan 31, 2010 2:48 PM in response to Rod Hagen

Hi Rod, thanks again.

I did add an aggregate device, and tried it again today to double-check, and the result is the same: It sounds like the audio has a crackly static.

Mike

Desperaudio Author

Level 1

0 points

Feb 2, 2010 6:54 AM in response to Rod Hagen

Hi Rod,

Sorry to bug you, but I thought you might like to know exactly what I'm trying to use the MacBook Pro for. I have a couple of websites with a lot of audio recordings:

http://www.americanaphonic.com
http://www.desperaudio.com

I hope to improve and develop the content of these sites with the editing mobility of a laptop. So I plug it in via the Toslink digital audio input port, grab the audio, break it down with an editing program called Twisted Wave, and present the audio to my employers. But this chain of events is broken at the first link, at plugging it into my studio.

So I'm in a bind, I'm not ranting or raving, and I think there's a solution out there. It's just a question of finding it. And I do appreciate your trying to help out.

Mike

Desperaudio Author

Level 1

0 points

Feb 15, 2010 4:44 PM in response to Desperaudio

I finally went out and bought another Toslink cable. This one was expensive (Monster brand) and I'm using the same 3.5mm adapter. It was an improvement, but not quite the solution. The previous Toslink cable was made by Belkin.

Now the Lunatec V3, with the Toslink mod, is working very well. I'm getting good, clear audio, without the crackle.

On the Mytek Stereo96 ADC, there is a big improvement in that the MacBook Pro consistently recognizes that there is a digital audio input. With the previous Toslink cable, it would oscillate between digital and analog. However, when recording, there is crackle. I can't seem to get clean audio. So now I am trying to figure out the difference between these two converters - the Grace Design Lunatec V3 and the Mytek Stereo96 ADC. It's possible that this problem is related to the converter signal rather than the MacBook Pro, however, it's still too early for any definitive conclusions.

And it is still a total mystery why the Belkin Toslink cable worked fine on all the iMacs and Mac Pros that I tried, but not on any of the MacBook Pros. I've actually ordered 4 more Toslink cables, each from a different company, and they should arrive throughout the week. I really want to get to the bottom of this mystery.

Desperaudio Author

Level 1

0 points

Feb 23, 2010 12:12 PM in response to Desperaudio

Okay, this is embarrassing to admit, but the problem was the 3.5mm adapter. I bought Toslink cables from 4 different sellers on eBay and tried them all out, and finally figured this out.

First, let me apologize for saying that the problem was the MacBook Pro. Apple has provided great customer service and the best gear I know of. I made the wrong conclusion because my 3.5mm adapter worked in every iMac I tried, but not in any MacBook Pro.

Second, thanks to DaddyPaycheck, who gave the first, and correct, response to my problem.

And lastly, thanks to Rod Hagen for trying to help out.

If there is a lesson here, it is to replace cables and connectors first, before moving on to more complex and expensive parts of the audio chain.

This thread has been closed by the system or the community team. You may vote for any posts you find helpful, or search the Community for additional answers.

Optical digital audio input port on MacBook Pro