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Topic: Problem with Digital Audio Out from Mac Mini (Read 19141 times) previous topic - next topic
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Problem with Digital Audio Out from Mac Mini

I am using a brand new Mac Mini (4GB RAM running OS 10.6.5) to run primarily FLAC audio tracks to my stereo system’s preamp, a McIntosh MX132 via the TOSLINK digital audio out.

The problem is that at the end of every song, it seems like the Mac Mini stops sending the audio signal to the preamp during the “gap” between songs, as evidenced by the L/R audio input indicator lights on the front of the preamp going out.  When the next song starts, it takes about 1-2 seconds to re-establish the connection (i.e., for the indicator lights come back on on the preamp) and so I don’t hear the first second or so of that next song.

This problem happens with both FLAC and ALAC files using Songbird and iTunes. It also happened when I used the VLC player software.

I am using two other TOSLINK audio inputs from my DVD player and Cable TV box, both with no problems. 

I have changed out the TOSLINK cables and switched the Mac audio output into the other 2 preamp TOSLINK inputs with no success.

Also, I tried a 3.5mm-to-dual RCA splitter and ran the analog audio out from the Mac Mini's headphone jack and it works fine.  So the issue is only with the TOSLINK digital/optical output.

I have tried different software audio players (iTunes, Songbird, VLC) and this happens with all 3. I have also tried both ALAC and FLAC files, which play fine on another computer (i.e., the song files definitely are OK).

I have also tried “gapless” playback and this does not solve the problem.

I've researched this online and can't find anyone with a similar problem. I'm hoping it's just something simple I'm overlooking. I have tried playing with the gapless and crossfade settings in iTunes but I think the issue is either with the audio out from the Mac Mini or how the preamp is handling the audio input via Toslink.

Any help would be greatly appreciated. Thanks.

Paul

Problem with Digital Audio Out from Mac Mini

Reply #1 –
Sounds like an issue with they way you amp deals with digital signal. I use 3.5mm-to-dual RCA splitter so i hooked up my MacMini to my amp via Toslink and can't recreate this issue with my MacMini, is it possible for you to try another Amp ? It could very well be the amp causing the problem.

Also try going to audio midi set up in the utlitiles folder and make sure the digitial output is set to 44100.hz and 2ch 24bit.

Problem with Digital Audio Out from Mac Mini

Reply #2 –
Do you have the same output sample rate set as the tracks are?

Problem with Digital Audio Out from Mac Mini

Reply #3 –
Thanks for the help, I have a few more questions as I try to solve this problem.

Quote from: Billytheonion on
Sounds like an issue with they way you amp deals with digital signal. I use 3.5mm-to-dual RCA splitter so i hooked up my MacMini to my amp via Toslink and can't recreate this issue with my MacMini, is it possible for you to try another Amp ? It could very well be the amp causing the problem.


I think it's at least partly the amp, it seems like it's slow to reconnect/sync with the audio output. 

Question: why do you use the analog audio output which is coming from the Mini's amplifier which I'm assuming is not very good?  I haven't done that (except to test) because I assumed the audio quality was low.  One solution I'm considering is to take the digital audio output and run it thru an external DAC (something like this: http://www.hirestech.com/products/), which then provides an analog output that my preamp should be able use without the digital switching problem.

Quote from: Billytheonion on
Also try going to audio midi set up in the utlitiles folder and make sure the digitial output is set to 44100.hz and 2ch 24bit.


Quote from: googlebot on
Do you have the same output sample rate set as the tracks are?


OK I see where in the Audio Midi setup I can adjust the digital output.  The output is set to 44100.hz and 2ch 24bit.

googlebot: I'm ripping my CDs into FLAC files using XLD and I don't see what the sample rate is.  I guess I just assumed they were at 44.1KHz but I'm trying to figure it out now.

Thanks again guys.. 

Problem with Digital Audio Out from Mac Mini

Reply #4 –
Quote from: pgm234 on
Question: why do you use the analog audio output which is coming from the Mini's amplifier which I'm assuming is not very good?  I haven't done that (except to test) because I assumed the audio quality was low.

You should not make this assumption.

Problem with Digital Audio Out from Mac Mini

Reply #5 –
Quote from: greynol on
Quote from: pgm234 on
Question: why do you use the analog audio output which is coming from the Mini's amplifier which I'm assuming is not very good?  I haven't done that (except to test) because I assumed the audio quality was low.

You should not make this assumption.


Ok, does than mean that in the case of the Mac mini it's not true?

The Mini's analog output from the headphone jack has been amplified by the Mini's internal amplifier.  So I'd be feeding an amplified signal into my stereo preamp.  Doesn't putting the Mini's amplifier into the process degrade the final output from my home speakers?

That's why I was looking into buying the external DAC/Music Streamer like the HRT model I cited. That way I could take a preamp audio output from the Mini (bypassing the Mini's internal amplifier), then do the DAC process in the HRT (or similar) box, and feed the analog audio (still preamp) signal into my stereo preamplifier.

So are my assumptions incorrect?

Thanks again for taking the time to help.

Problem with Digital Audio Out from Mac Mini

Reply #6 –
I use the analog audio output because i don't use my MacMini for anything that requires surround sound.  It may feel it doesn't  sound as good because the output levels are pretty low. If you were to volume match the digital with analog you would be hard pressed to hear a difference thats if you even could.

Problem with Digital Audio Out from Mac Mini

Reply #7 –
pgm234,

Please read TOS #8 and the following thread:
http://www.hydrogenaudio.org/forums/index....showtopic=16295

They should be kept in mind when trying to justify assumptions about audio quality.

Problem with Digital Audio Out from Mac Mini

Reply #8 –
What i actually do is use the analogue out into my amps Main In, sounds amazing and the Mac can be used to control the volume.

Problem with Digital Audio Out from Mac Mini

Reply #9 –
I don't know enough about this stuff so I'm learning I shouldn't make assumptions about what will sound good and what won't until I try it.

Problem with Digital Audio Out from Mac Mini

Reply #10 –
You should also be aware that you cannot be sure of what you actually hear if you know ahead of time which setup you're listening to.  If you have some type of expectation bias your brain can and often will play tricks on you.

Problem with Digital Audio Out from Mac Mini

Reply #11 –
Quote from: Billytheonion on
What i actually do is use the analogue out into my amps Main In, sounds amazing and the Mac can be used to control the volume.


Billy, thank you again for taking the time to help me.  I'm going to try to do an unbiased sound comparison. It would be great to save the cost of the external DAC if it doesn't improve the sound quality.  And your solution definitely solves the main problem I have with my preamp being slow in resyncing with the audio input.

Problem with Digital Audio Out from Mac Mini

Reply #12 –
Another solution is to use a Airport Express, that will bypass the MacMini's internal sound processor, some say this is the way to go to get the best possible sound. I honestly can't hear any difference between that and going straight from the analogue our to my amps Main In. If your amp doesn't have a Main In then APE may be the cheapest solution.

Edit: The Apple TV is  cheaper than the APE and will do the same thing plus so many extra features.

Problem with Digital Audio Out from Mac Mini

Reply #13 –
Normally a CD is ripped to its native bit depth and sample rate: 16 bits / 44.1 kHz
You might try these settings in the audio midi.

Some audio drivers do mute the digital out between tracks.
If for some reason the McIntosh is very slow in locking on the signal this might explain the drop-out.
However I would expect this not to happen in case of gapless playback.
If you connect the 2 analogue, is gapless really gapless?

I also expect this to happen at the beginning of the very first song.
No ‘enhancements’ active like fading?

TheWellTemperedComputer.com

Problem with Digital Audio Out from Mac Mini

Reply #14 –
Quote from: Billytheonion on
some say this is the way to go to get the best possible sound.

Not to belabor the point but some also say you need magic pebbles to get the best possible sound.

Problem with Digital Audio Out from Mac Mini

Reply #15 –
Is anyone actually silly enough to believe that pebbles are magical and can improve sound.

Problem with Digital Audio Out from Mac Mini

Reply #16 –
Unfortunately yes and for this reason I think the old "some say" does a disservice to this community.  Let's stick to verifiable facts, please.  If you have objective evidence that an APE does a better job converting digital to analog than a Mac Mini then feel free to present it.

Problem with Digital Audio Out from Mac Mini

Reply #17 –
I have no evidence, i doubt very much i could come up with any, i personally can't tell the difference between the MacMini or APE. No scientific tests but it all sounds the same to me. I just suggested the APE as a way to overcome their issue.

Problem with Digital Audio Out from Mac Mini

Reply #19 –
Quote from: pgm234 on
I am using a brand new Mac Mini (4GB RAM running OS 10.6.5) to run primarily FLAC audio tracks to my stereo system’s preamp, a McIntosh MX132 via the TOSLINK digital audio out.

The problem is that at the end of every song, it seems like the Mac Mini stops sending the audio signal to the preamp during the “gap” between songs, as evidenced by the L/R audio input indicator lights on the front of the preamp going out.  When the next song starts, it takes about 1-2 seconds to re-establish the connection (i.e., for the indicator lights come back on on the preamp) and so I don’t hear the first second or so of that next song.


Just now remembering some time ago I read a Stereophile review of the Airport Express reporting this same behavior and in fact they attributed the problem to the ceasing of digital signal output from the device between two songs, coupled to the delay of the feeded DAC to resync in time from the start of the next song.

Here's the exact excerpt:<<One operational glitch that didn't affect my system to any significant extent but did do so for some readers was the fact that, as the AE doesn't have a local clock circuit, when the incoming data is interrupted, as it is when you change songs in iTunes, there is no longer a digital output to feed the DAC, which loses lock as a result. Both the Levinson and the Benchmark DACs that I use deal gracefully with the lost lock and are quick to unmute when the new song is sent to the AE. I therefore missed the fact that with some other DACs, the first seconds of a song might be cut off.>>
... I live by long distance.

Problem with Digital Audio Out from Mac Mini

Reply #20 –
Quote from: Billytheonion on
Another solution is to use a Airport Express, that will bypass the MacMini's internal sound processor...


There is no sound processing in a Mac mini, when the digital output is used, the sample rate matches, and volume is set to 100%.

I suspect the McIntosh to employ some queer sample rate detection mechanism. S/PDIF normally doesn't know a "connection" state, samples are supposed to be played as they come. Maybe the McIntosh tries to "improve" this simple mechanism by trying to detect the sample rate for reclocking and then chokes on a microsecond delay between the end of the last and start of the next track. I would seriously reconsider using the McIntosh for D/A conversion if you cannot identify audible benefits.

Problem with Digital Audio Out from Mac Mini

Reply #21 –
Quote from: googlebot on
I suspect the McIntosh to employ some queer sample rate detection mechanism. S/PDIF normally doesn't know a "connection" state, samples are supposed to be played as they come. Maybe the McIntosh tries to "improve" this simple mechanism by trying to detect the sample rate for reclocking and then chokes on a microsecond delay between the end of the last and start of the next track. I would seriously reconsider using the McIntosh for D/A conversion if you cannot identify audible benefits.


I'm pretty convinced that you're right, my problem is with the McIntosh's limitations in handling the digital/optical audio input.

So I think I've narrowed this down to two solutions.

1. Feed audio from the Mac Mini's headphone jack using a 3.5mm-to dual RCA splitter into the analog input of my preamp.  Alternately, I could take the Mini's audio output from its USB port to an external USB DAC, and from there run analog R/L audio cables to the preamp.  If I use the external DAC, I should still be able to use the Mini's digital/optical output for movies as the issue with the delayed sync between the Mini and my preamp is not important with movies (I don't care if I miss the first second of a movie's audio). So for the movie side, I still can have 5.1 audio output to the preamp.

2. It was suggested to me that AppleTV would work, that its digital/optical output would not cause the sync delay problem.  It's only $99 and if it doesn't work I can always return it.  However, the ATV choice carries pluses and minuses. First, my 1000+ album collection is all in FLAC. I could run Fluke under iTunes or use Max and convert everything to ALAC. I haven't tried Fluke but it seems like some users at least have had issues and it's just another added complexity.

Also, I've been using Songbird and I really like it. iTunes seems to be a step backwards, especially with a large music collection as its sorting capabilities seem limited, but maybe I just need to play with it more.

The advantages of going the ATV/iTunes route are: (1) hopefully the ATV output solves my optical input problem; (2) I get to use the features of ATV (I'm just not sure I need/want any of them); (3) I have an all-Apple solution so hopefully future technical issues are minimized, as opposed to a mix of systems and apps; (4) the ATV user interface is easy and my wife will like it.

Anyway, thank you again to everyone for the terrific help.  I think I’m close to having this issue solved.

Problem with Digital Audio Out from Mac Mini

Reply #22 –
Quote from: greynol on
Unfortunately yes and for this reason I think the old "some say" does a disservice to this community.  Let's stick to verifiable facts, please.  If you have objective evidence that an APE does a better job converting digital to analog than a Mac Mini then feel free to present it.


There are different utterances in which "some people say" occurs. If billytheonion had said "Some people say magic pebbles improve SQ, so you might try that," he would clearly have been trying to sneak round TOS #8. But he actually said "S.p.s.t. <x is better>, but I can't hear it." In that case, s.p.s.t. is clearly equivalent to "You will find some claims on the internet or in magazines," which is an entirely empirical statement, especially as the obvious implication of "but I can't hear them" is that such claims should be subjected to test.

Objecting to forms of words, rather than what the words are used to say, can end up in a Scunthorpe situation.

Problem with Digital Audio Out from Mac Mini

Reply #23 –
He did in fact offer up the AirPort Express as a solution, though I don't think he was intentionally trying to sneak around TOS #8 and to be clear, I was not calling him out on a TOS #8 violation; rather I was attempting to inquire as to whether he noticed that people making such claims also had objective evidence supporting their position.  Somehow this is wrong but yet it is perfectly fine to drop the idea that magic pebbles might improve sound quality so long as I stipulate that I don't have the ability to tell the difference?

Let's talk about the spirit of what I was trying to get across instead of nitpicking the language that I used.  Would I have garnered your approval if I had said, "I find third-party claims about needing an AirPort Express to get the best sound quality dubious and would like to see some objective evidence in order to take them seriously.  I think this community is better served without their presentation if they cannot be substantiated in accordance with our Terms of Service."?

If billytheonion feels that I was accusing him trying to avoid a TOS #8 violation then I extend my apologies, though it is pretty clear to me from his response that he did not take it that way at all.  On the contrary, it seemed quite obvious that he was extending at least some credibility to what others have been saying.  Again, if this assumption is wrong I further apologize to him.  Perhaps I should have prefaced my reply which you found offensive with an acknowledgment that he took the time to suggest differences between alternate solutions are probably not audible as far back as his second reply in addition to crediting him with identifying the problem in the very first reply to this discussion.

Problem with Digital Audio Out from Mac Mini

Reply #24 –
Yea sorry about that, didn't realise they lowered the price of the the APE, i still feel the Apple Tv is a better buy only  few extra $$ and so much functionality.

Quote" There is no sound processing in a Mac mini, when the digital output is used, the sample rate matches, and volume is set to 100%." In my poor english way thats what i meant.

No i don't feel that anyone was accusing me on anything, i understand what Greynol was getting at. Lots of claims are rubbish and that  there is no need to bring them up here. Just because people say this is better doesn't mean it is, especially with no evidence. 

Converting all your Flacs to ALAC is an option and using iTunes. If you need any help organising iTunes sing out, i find it has more than enough options to keep your music very well organised. I do have an Apple Tv 2 and it doesn't cause the signal to drop out, so hopefully that solves your issue. Once it's set up there is no need to have the TV on either and can be controlled via your computer or an iDevice iPod Touch iPhone or iPad.