Mac Mini, iTunes & high resolution audio

[robdrums2097]

Hi all,

 

First post from a regular loiterer (if that isn't a word, it is now). I've always been impressed by the balance of passion & realism on these forums, so I'm going to give a question I have a shot.

 

So I've just ordered a pretty much full spec Late 2014 Mac Mini, with i7, 16GB & 2TB Fusion Drive. Its main use will be music, connected by optical to my Cambridge Audio AV receiver via its digital audio output. This has a 192/24 capable Cirrus Logic DAC, that should be perfectly capable without the need for a separate upsampling DAC (of which I have one - a DACMagic Plus - but am looking to 'slim down'. I can't hear any particular benefit over my receiver's DAC apart from the filter adjusters). I'm keeping the DACM for now in case I do decide to revert to it. But it'll probably end up on eBay.

 

Anyway, Google searches bring up many articles & threads that I believe to be outdated. I don't really want to start buying & wasting time & computer resources with plug-ins, apps & alternative players (JRiver, Audirvana, Pure Music & the like) if I can help it. I'm happy to keep things simple with the standard Mac setup & iTunes.

 

Although I enjoy & respect good quality, I'm not the sort that sits listening critically for / imagining 'sound stages' and the minutest of details in my music when using different DACs, cables, players and things. I just want things to work & to work well with good sound and to enjoy my music, hence coming to my first Mac after years of PC use.

 

But I want to both get decent sound quality (obviously) and get into HDTracks and listen to high res ALAC files.

 

My question is this: if the output is set accordingly in the MIDI & iTunes menus, will the 2014 Mini with current software & Yosemite output a 192/24 signal? The vast majority of my music is ripped at 44.1/16 ALAC from CDs. Will this music either be upsampled (detrimentally or improved) if MIDI is set to 192/24, or worse, will it downsample high res stuff to the same if set lower? Or is the Mac / iTunes clever enough (these days, where I know it didn't used to be) to automatically change this setting on the fly? Or theoretically, if I understand what I've read about the likes of BitPerfect plugins, would I need to manually adjust the MIDI settings each time I play a high res track, or vice versa if set accordingly (far from ideal, obviously)?

 

Will iTunes serve me well enough as an above average but not fanatical amateur audiophile? (I've no objection to its interface, I use Home Sharing and need it unavoidably for iOS management. Plus it's of course free) Or do I need to use something like JRiver or Audirvana to manage a large collection of varied sample rate music to hear everything seamlessly as it's meant to be heard? I've a feeling from what I've been reading that I've been doing it wrong for years through Windows iTunes, and that all music was probably outputting at the same quality, with some funny processing up and down going on to compensate.

 

Many thanks in advance for any advice.

 

Rob

[goldsdad]

My question is this: if the output is set accordingly in the MIDI & iTunes menus, will the 2014 Mini with current software & Yosemite output a 192/24 signal? The vast majority of my music is ripped at 44.1/16 ALAC from CDs. Will this music either be upsampled (detrimentally or improved) if MIDI is set to 192/24, or worse, will it downsample high res stuff to the same if set lower? Or is the Mac / iTunes clever enough (these days, where I know it didn't used to be) to automatically change this setting on the fly?

 

iTunes hasn't changed. (By the way, the setting you're talking about has nothing to do with MIDI. Audio MIDI Setup Utility is for Audio and MIDI settings, and you're dealing with the audio settings, not MIDI settings.)

 

Or theoretically, if I understand what I've read about the likes of BitPerfect plugins, would I need to manually adjust the MIDI settings each time I play a high res track, or vice versa if set accordingly (far from ideal, obviously)?

 

To ensure no resampling at all in the computer when using straight iTunes , the output rate in Audio MIDI Setup must be matched to the rate of the files about to be played while iTunes is closed, otherwise there will be two potential stages of resampling - one by iTunes and a subsequent one by the OS before audio is sent to a device. Explanation: iTunes doesn't output directly to an audio device driver - it outputs to the OS and the OS outputs to a device driver. When iTunes is launched, it sets its output rate (the sample rate of the audio data it sends to the OS) to match the output rate of the OS (which can be seen/set in Audio MIDI Setup). If the OS rate is changed while iTunes is open, iTunes knows nothing about that change, the iTunes output rate remains as it was when launched, and there will be resampling by iTunes if the file's rate doesn't match iTunes rate, and resampling by the OS when the iTunes rate doesn't match the OS rate.

 

I think you should try setting the rate in Audio MIDI Setup to the maximum supported by the connection to your DAC/receiver, so that resampling will occur for files of any different rate, and seeing whether you find the sound acceptable. If happy with the sound, then you can relax and enjoy the music with no fuss or extra software.

 

Regarding the optical connection, the newest Mac minis can output 192 kHz over optical but are you sure about the receiver's optical input? It's quite likely, but not definite, that the receiver's optical input has a maximum of 96 kHz. Also be aware that not all optical cables will faithfully transport 192 kHz.

[Musicophile]

If you want to stick with iTunes i strongly recommend you invest at least $10 for Bitperfect as it takes away the sample rate changing hassle.

 

You can always experiment with other players later.

[orgel]

If you want to stick with iTunes i strongly recommend you invest at least $10 for Bitperfect as it takes away the sample rate changing hassle.

 

+1 on this. Audirvana+ is my personal favorite, but I was recently hanging out at an audio dealer's in my area, and it emerged that he was using the iTunes/BitPerfect combination in his most upscale room (dCS stack, Wilson Alexandria XLF's) because he needed "something bulletproof" for his demos.

 

--David

[robdrums2097]

Thanks all. To say I'm finding this all a headache that almost just convinces me to stick with CD quality would be an understatement!

 

I'm not averse necessarily to using another player - JRiver does possibly look interesting, for example - but at £7.99 for each app download of the remote, it'd need to present a very convincing case to make it worthwhile considering 95% of my collection is CD.

 

I could use USB if I resumed use of the DACMagic, or HDMI if I changed my rig to go through the receiver (it currently goes straight to the TV, so the optical was the preferred choice for audio to my amp). On PC at least I always had very variable results using both of these connections, sound quality- and stability- wise.

 

If iTunes + BitPerfect will work seamlessly & faultlessly with OSX (and hopefully with El Capitan when it's released), then perhaps this is the way to go.

 

I think optical is capped at 96khz, so even if the software, the OS, the cable & the receiver input were all perfect, it seems it isn't possible.

 

Makes you wonder, a bit like 'HD Ready' TVs, that patently weren't true HD or ever displaying an HD picture, even though their users thought they were a part of the future, how many people are paying for and running high definition audio and not actually getting it through the speakers as I have been!

[Melvin]

snip ...

 

If iTunes + BitPerfect will work seamlessly & faultlessly with OSX (and hopefully with El Capitan when it's released), then perhaps this is the way to go.

 

I'm just going to play Devil's advocate on this if you don't mind. BitPerfect did not always play nice in my system. Is it worth the $10? Absolutely! Is it without issue? No. FWIW, every player, including iTunes, has some gremlins.

 

Welcome to the madness.

[robdrums2097]

Regarding the optical connection, the newest Mac minis can output 192 kHz over optical but are you sure about the receiver's optical input? It's quite likely, but not definite, that the receiver's optical input has a maximum of 96 kHz. Also be aware that not all optical cables will faithfully transport 192 kHz.

 

Also, this article lists the late 2014 MM as ablel to output 192khz (but not the 2012 and before), so I'm guessing something has changed in there:

 

https://support.apple.com/en-us/HT202730

 

I'm not sure how I'd know what the receiver's optical socket is capable of, but I'd assume (not safely, but ish) if the internal DAC is quoted as 192/24 capable, then the inputs SHOULD be, no? I could check with Cambridge Audio, I suppose.

 

Whilst I could resume use of my DacMagic, which has asyncrous USB and upsampling, I really don't want to if I can get a good result straight from the amp...

 

Rob

[kirkmc]

Also, this article lists the late 2014 MM as ablel to output 192khz (but not the 2012 and before), so I'm guessing something has changed in there:

 

https://support.apple.com/en-us/HT202730

 

I'm not sure how I'd know what the receiver's optical socket is capable of, but I'd assume (not safely, but ish) if the internal DAC is quoted as 192/24 capable, then the inputs SHOULD be, no? I could check with Cambridge Audio, I suppose.

 

Rob

 

That's not the internal DAC; that's what you see when you have a DAC capable of 192 kHz connected to the device. I have the newest iMac, and my DAC only goes to 96, and that's the highest I see in Audio-MIDI Setup.

[robdrums2097]

That's not the internal DAC; that's what you see when you have a DAC capable of 192 kHz connected to the device. I have the newest iMac, and my DAC only goes to 96, and that's the highest I see in Audio-MIDI Setup.

 

 

Sorry, I meant the internal DAC of the receiver, not the Mac.

 

Is your iMac listed in this list - if so, I really can't see how they could sell it as 192 capable unless they stated that their OS limits to 96...

 

https://support.apple.com/en-us/HT202730

 

 

Rob

[goldsdad]

I'm not sure how I'd know what the receiver's optical socket is capable of, but I'd assume (not safely, but ish) if the internal DAC is quoted as 192/24 capable, then the inputs SHOULD be, no?

 

No.

 

192 kHz optical input is possible, but far from a safe assumption. For example my DAC internally upsamples to 384 kHz, but the inputs are limited to 96 kHz optical S/PDIF, 192 kHz electrical S/PDIF and 48 kHz USB.

 

I could check with Cambridge Audio, I suppose.

 

Yes, check with Cambridge Audio.

[Bill Brown]

Many DACs will post the sample rate capability for different input formats (optical v SPDIF v USB, etc.).

 

Simply connect the mini to your receiver with optical, if 192/24 is available you will see this sample rate as an option in Audio-MIDI set-up. If it is available and music comes out without glitches, it is capable, otherwise you are likely to be limited to 96K.

 

As others suggest, all of the programs that adjust the sample rate for bit-perfect playback have little gremlins in operation. If you set Audio-MIDI to the highest rate your receiver can receive and enjoy the sound, then just enjoy and be happy (or try Bit Perfect and see if it functions adequately to not disrupt your enjoyment)

[LCC0256]

iTunes hasn't changed. (By the way, the setting you're talking about has nothing to do with MIDI. Audio MIDI Setup Utility is for Audio and MIDI settings, and you're dealing with the audio settings, not MIDI settings.)

 

 

 

To ensure no resampling at all in the computer when using straight iTunes , the output rate in Audio MIDI Setup must be matched to the rate of the files about to be played while iTunes is closed, otherwise there will be two potential stages of resampling - one by iTunes and a subsequent one by the OS before audio is sent to a device. Explanation: iTunes doesn't output directly to an audio device driver - it outputs to the OS and the OS outputs to a device driver. When iTunes is launched, it sets its output rate (the sample rate of the audio data it sends to the OS) to match the output rate of the OS (which can be seen/set in Audio MIDI Setup). If the OS rate is changed while iTunes is open, iTunes knows nothing about that change, the iTunes output rate remains as it was when launched, and there will be resampling by iTunes if the file's rate doesn't match iTunes rate, and resampling by the OS when the iTunes rate doesn't match the OS rate.

 

I think you should try setting the rate in Audio MIDI Setup to the maximum supported by the connection to your DAC/receiver, so that resampling will occur for files of any different rate, and seeing whether you find the sound acceptable. If happy with the sound, then you can relax and enjoy the music with no fuss or extra software.

 

Regarding the optical connection, the newest Mac minis can output 192 kHz over optical but are you sure about the receiver's optical input? It's quite likely, but not definite, that the receiver's optical input has a maximum of 96 kHz. Also be aware that not all optical cables will faithfully transport 192 kHz.

 

Thank you so much for this information. I am basically in the same boat as the OP and have wondered this EXACT THING for more time than i would like to admit. For whatever reason i have never been able to locate such a brief cogent & precise explanation of iTunes/OS interface as it relates to SQ anywhere on the net...Somehow this post by Goldsdad needs to be put in a place so all Apple users who are not as sophisticated as most of the regular posters on here can reference easily. Again like the OP i lurk about on this site to TRY to glean some pertinent (for me and my hearing/listening abilities) information regarding what may improve my listening experience. I never fail to learn SOMETHING new and interesting here. Thank you again Goldsdad.

[goldsdad]

Thank you so much for this information. [...]

 

You're welcome!

[kirkmc]

iTunes does not resample; in fact, iTunes doesn't process audio at all. On Macs, it's the CoreAudio framework that does all the work, iTunes simply tells it to change things like volume and EQ, if any is set. I assume this is the same on Windows; there must be a similar system audio framework that's used, or iTunes uses QuickTime, which is essentially CoreAudio.

[goldsdad]

iTunes does not resample; in fact, iTunes doesn't process audio at all. On Macs, it's the CoreAudio framework that does all the work, iTunes simply tells it to change things like volume and EQ, if any is set. I assume this is the same on Windows; there must be a similar system audio framework that's used, or iTunes uses QuickTime, which is essentially CoreAudio.

 

Thanks for posting, Kirk. I've just checked the behaviour of iTunes 12.1.2 on OS X 10.9.5, and there is only one stage of resampling between file and the device driver, i.e. no iTunes resampling.

 

Being certain that this was not the case some time ago, I then rechecked iTunes 10.2.2 on OS X 10.6.8, and that definitely exhibits the two stages of resampling that I described earlier. So there has been a change in the past few years that I didn't realize.

[Musicophile]

I'm just going to play Devil's advocate on this if you don't mind. BitPerfect did not always play nice in my system. Is it worth the $10? Absolutely! Is it without issue? No. FWIW, every player, including iTunes, has some gremlins.

 

Welcome to the madness.

Sad to hear this. it used to be quite stable in the past but I haven't used it once since A+ 2.0

[Melvin]

Sad to hear this. it used to be quite stable in the past but I haven't used it once since A+ 2.0

 

It's been a while since I've used it but I removed it from my 2 Mac minis after an "update" to the app and haven't used it since.

[robdrums2097]

Thanks for all the input. Cambridge Audio have confirmed that the optical inputs are restricted to 24/96. Which is probably fine, if disappointing as it seems to cost much the same to download that as a 192 file.

 

SO... Why do we never talk about using HDMI, as this must be perfectly capable of the data rates required, is connected directly to my receiver already, and I'd have thought is more geared up than USB for high resolution audio considering we use it every day for DTS & DD Blu Ray 24 bit audio?

 

And am I crazy to own a DACMagic Plus with USB & be too lazy to use it (it too has often not been gremlin-free in use, especially with USB, in my three years of use with it on my PC. Funny noises, input drops, PC driver issues... Oh for a quiet life!)...

 

Rob

[Melvin]

snip...

 

SO... Why do we never talk about using HDMI, as this must be perfectly capable of the data rates required, is connected directly to my receiver already, and I'd have thought is more geared up than USB for high resolution audio considering we use it every day for DTS & DD Blu Ray 24 bit audio?

 

I believe cost is the biggest factor:

 

What are the Licensing Costs Associated with HDMI?

[robdrums2097]

OK, but if we have an HDMI output from our Mac Mini and an HDMI input on our receiver, that doesn't affect us, does it? That would seem to be a way for me to get 192/24 audio AND HD video at the same time without even using the optical. Or am I missing something?

 

Rob

[Melvin]

OK, but if we have an HDMI output from our Mac Mini and an HDMI input on our receiver, that doesn't affect us, does it? That would seem to be a way for me to get 192/24 audio AND HD video at the same time without even using the optical. Or am I missing something?

 

Rob

 

No of course not. Sorry, my brain was thinking along the lines of smaller audiophile-centered manufacturers not wanting to pay the licensing fees.

[kirkmc]

Thanks for posting, Kirk. I've just checked the behaviour of iTunes 12.1.2 on OS X 10.9.5, and there is only one stage of resampling between file and the device driver, i.e. no iTunes resampling.

 

Being certain that this was not the case some time ago, I then rechecked iTunes 10.2.2 on OS X 10.6.8, and that definitely exhibits the two stages of resampling that I described earlier. So there has been a change in the past few years that I didn't realize.

 

And how are you seeing this? I've always understood that iTunes just routes the files through CoreAudio, and doesn't do anything, other than specify a volume and an EQ (if any).

 

Or, does in resample if Sound Check is on? I'd still expect that to only happen in CoreAudio.

[goldsdad]

And how are you seeing this? I've always understood that iTunes just routes the files through CoreAudio, and doesn't do anything, other than specify a volume and an EQ (if any).

 

Or, does in resample if Sound Check is on? I'd still expect that to only happen in CoreAudio.

 

 

I'm seeing this by capturing the audio before it gets to the output audio device driver. All my tests are done at 100% volume and without Sound Check or Equalizer.

 

 

For example, set sample rate in Audio MIDI Setup (AMS) to 44.1 kHz, then launch iTunes 10.2.2 (OS X 10.6.8), play a full-bandwidth 96 kHz fs file and capture: the captured audio has a 44.1 kHz fs as expected.

 

 

Without closing iTunes, stop playback and set AMS rate to 96 kHz, restart playback and capture: the captured audio has 96 kHz fs, but contains nothing above the 22.05 kHz Nyquist frequency of an initial 44.1 kHz fs downsampling.

 

 

Close iTunes and relaunch iTunes while AMS is at 96 kHz, and play the 96 kHz fs file: captured playback has 96 kHz fs, and is full-bandwidth and bit-perfect.

 

Now play a 44.1 kHz file and capture: captured playback is 96 kHz fs, but containing frequencies limited to the 22.05 kHz of the original file.

[kirkmc]

I'm seeing this by capturing the audio before it gets to the output audio device driver. All my tests are done at 100% volume and without Sound Check or Equalizer.

 

 

For example, set sample rate in Audio MIDI Setup (AMS) to 44.1 kHz, then launch iTunes 10.2.2 (OS X 10.6.8), play a full-bandwidth 96 kHz fs file and capture: the captured audio has a 44.1 kHz fs as expected.

 

 

Without closing iTunes, stop playback and set AMS rate to 96 kHz, restart playback and capture: the captured audio has 96 kHz fs, but contains nothing above the 22.05 kHz Nyquist frequency of an initial 44.1 kHz fs downsampling.

 

 

Close iTunes and relaunch iTunes while AMS is at 96 kHz, and play the 96 kHz fs file: captured playback has 96 kHz fs, and is full-bandwidth and bit-perfect.

 

Now play a 44.1 kHz file and capture: captured playback is 96 kHz fs, but containing frequencies limited to the 22.05 kHz of the original file.

 

Hmmm... That still doesn't prove that iTunes is resampling. It suggests that there's a glitch somewhere, but I don't think there's anything in iTunes' code to resample. In fact, it would surprise me if that were the case, since having two resamplings means that it's much harder to update the code for both iTunes and CoreAudio.

 

Does this also happen with iTunes 11 or 12?

 

And what software do you use to capture the audio and verify the frequency range? I'd like to test this myself. If this is the case, this is actually something I should write about on my website.

[goldsdad]

Hmmm... That still doesn't prove that iTunes is resampling. It suggests that there's a glitch somewhere, but I don't think there's anything in iTunes' code to resample. In fact, it would surprise me if that were the case, since having two resamplings means that it's much harder to update the code for both iTunes and CoreAudio.

 

iTunes (or any other Mac app) wouldn't need to contain its own resampling code in order to resample. Apps can utilise functions and services provided by the Core Audio frameworks.

 

Does this also happen with iTunes 11 or 12?

 

As I said earlier, the two-stage resampling didn't happen in 12.1 on OS X 10.9.5 when I tested it following your first post regarding Core Audio in this thread. That was a surprise to me because it differed from my previous testing of iTunes years ago (which confirmed what others had been writing back then). So I retested 10.2.2 on a OS X 10.6.8 volume that I seldom use nowadays, and found the two-stage resampling as expected. I have no other versions of iTunes to test.

 

And what software do you use to capture the audio and verify the frequency range? I'd like to test this myself. If this is the case, this is actually something I should write about on my website.

 

An old version of Audio Hijack Pro and Audacity on OS X 10.6.8, the current Audio Hijack and Audacity on OS X 10.9.5.