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Standard User caffn8me
(eat-sleep-adslguide) Mon 24-Jul-17 19:37:37
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Re: iTunes sound quality rant


[re: Zarjaz] [link to this post]
 
Are you using headphones or speakers to listen to iTunes? It's possible that speakers will be less revealing.

Sarah

--
If I can't drink my bowl of coffee three times daily, then in my torment, I will shrivel up like a piece of roast goat

Spiders on coffee - Badass spiders on drugs
Standard User caffn8me
(eat-sleep-adslguide) Mon 24-Jul-17 22:49:28
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Re: iTunes sound quality rant


[re: Zarjaz] [link to this post]
 
Well, I've been playing around - but I haven't got my distortion meter out yet.

I've downloaded Vox and Quod Libet audio players. I've opted for the latter because I much prefer the interface.

I get distortion (and I can reproduce this at exact points in the music) on iTunes regardless of how I play the music back - optical cable to DAC, USB cable to DAC or streaming via Airplay. Playback via USB DAC, which works better than optical, is nastily bright and significantly distorted right from the first chords of Sharon Isbin's Journey to the New World - which is acoustic guitar. It's very unpleasant and not at all realistic, and it distorts regardless of what the iTunes volume control is set to.

Playing the same tracks via Vox or Quod Libet and the optical connection reduces distortion but there is still a tiny amount on peaks. The sound is a bit wooly.

With Quod Libet on USB DAC the sound is more natural and open, has extended bass and no distortion (except for one moment which I suspect is the actual recording), even when the headphones are cranked up high. It's got a better sense of space and 'being there'.

Then I re-ripped it from the CD to FLAC using XLD with no compression and it's audibly better still. The TEAC HR Audio app improves things even further.

Interestingly, when all apps are set to maximum playback level, they're all the same volume except for iTunes - which plays back much louder.

Both Quod Libet and Vox can play all the files from your iTunes library so I'd suggest you try them and see if you can hear a difference.

I'm still of this opinion that iTunes is just plain nasty.

Sarah

--
If I can't drink my bowl of coffee three times daily, then in my torment, I will shrivel up like a piece of roast goat

Spiders on coffee - Badass spiders on drugs
Standard User caffn8me
(eat-sleep-adslguide) Wed 26-Jul-17 00:49:28
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Re: iTunes sound quality is officially pants


[re: billford] [link to this post]
 
Well, I've started again. I've updated to the latest iTunes which came out this week - 12.6.2.20

I then used Audacity to generate a clean 1kHz audio file at the maximum level with 16bit 44.1kHz sampling - exactly the same as a CD.

With the Audacity Distortion Analyser plug-in I confirmed this had no significant distortion (measured at 0.002% THD). This measurement plug-in may not be 100% accurate but it means I don't introduce more distortion from replaying via DAC to analogue through a headphone amplifier.

I saved the 1kHz tone as an AIFF format file which has no compression and is natively supported by iTunes as well as Quod Libet. Playing this back in Audacity showed the same distortion of 0.002% - effectively zero.

Using Soundflower I could then take the system sound and redirect it back into the Mac rather than sending it via a headphone or USB output. This allowed me to record the playback of the AIFF file from iTunes and Quod Libet into Audacity for analysis.

I knew iTunes was bad to my ears, but the measurements were incredible. Below are screen shots of the analysis.

First of all - the raw Audacity file;

The Quod Libet replay performance;

The iTunes replay performance;
Cupertino, we've had a problem!

One thing that is immediately obvious listening to the iTunes replay of the AIFF file is the variation in level throughout. This is shown very clearly when you compare the first graph for each group. The frequency spectrum shows why iTunes sounds so bad - an absolutely huge and totally unacceptable amount of harmonic distortion.

If anyone would like to play around, I've uploaded the 1kHz 30 second AIFF file (2.6MB);
WARNING: this is a high level audio signal so turn your speakers/headphones all the way down before playing it and increase the level slowly. Play it with iTunes and another replay app such as Quod Libet or Vox and let me know if you can hear a difference.

Next week I should be able to test on a relatively new iMac running Sierra. I'm not holding out for much of an improvement.

Sarah

--
If I can't drink my bowl of coffee three times daily, then in my torment, I will shrivel up like a piece of roast goat

Spiders on coffee - Badass spiders on drugs


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Standard User ukhardy07
(knowledge is power) Wed 26-Jul-17 01:14:01
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Re: iTunes sound quality is officially pants


[re: caffn8me] [link to this post]
 
I notice no variation throughout on a macbook pro retina 2014. I also cannot hear any distortion when listening to music via iTunes. I have tried the other sound players mentioned and cannot identify any differences. Are you sure you don't have some weird setting in itunes such as volume leveling, eq, sound check etc?
Standard User caffn8me
(eat-sleep-adslguide) Wed 26-Jul-17 01:24:57
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Re: iTunes sound quality is officially pants


[re: ukhardy07] [link to this post]
 
I am absolutely certain there are no weird settings in iTunes. When I turned audio tweaks on, the sound was worse. I'm currently on OS X 10.11.6. Perhaps that makes a difference.

Sarah

--
If I can't drink my bowl of coffee three times daily, then in my torment, I will shrivel up like a piece of roast goat

Spiders on coffee - Badass spiders on drugs
Standard User caffn8me
(eat-sleep-adslguide) Wed 26-Jul-17 02:11:34
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Re: iTunes sound quality is officially pants


[re: ukhardy07] [link to this post]
 
Here you go;

iTunes audio enhancer enabled and set minimum;

iTunes audio enhancer enabled and set to mid;

iTunes audio enhancer enabled and set to max;
So, the audio enhancer actually makes a difference. It sounds particularly nasty on the mid (default) setting. This is borne out by the measurements. The spectrum is particularly interesting.

Sarah

--
If I can't drink my bowl of coffee three times daily, then in my torment, I will shrivel up like a piece of roast goat

Spiders on coffee - Badass spiders on drugs
Standard User billford
(elder) Wed 26-Jul-17 08:30:04
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Re: iTunes sound quality is officially pants


[re: caffn8me] [link to this post]
 
I'm with ukhardy- I can't hear any problems with iTunes on any file.

I downloaded your 1kHz file- it sounded the same in both iTunes and Audacity. (And in VLC, QT and QT7, fwiw.)

I used Audio HiJack to capture and save the outputs from iTunes and Audacity (as uncompressed AIFF) and used Audacity to look at the spectrums- both the same, a single peak at 1kHz and no visible harmonics.
In reply to a post by caffn8me:
Cupertino, we've had a problem!
Sorry, but I think you've got a problem. Maybe hardware, maybe software, and I've no idea where to start looking.

But as an easy first shot, have you tried deleting the iTunes preference files?

Bill
A level playing field is level in both directions.

_______________________________________Planes and Boats and ... ______________BQMs: IPv4 IPv6

Edited by billford (Wed 26-Jul-17 09:35:58)

Standard User billford
(elder) Wed 26-Jul-17 08:53:19
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Re: iTunes sound quality is officially pants


[re: billford] [link to this post]
 
As an afterthought- I didn't need to take any care over the iTunes volume setting, the file played at the usual level.

I've got the "Sound Check" box ticked in preferences, maybe there's a problem there in your setup?

Bill
A level playing field is level in both directions.

_______________________________________Planes and Boats and ... ______________BQMs: IPv4 IPv6
Standard User caffn8me
(eat-sleep-adslguide) Wed 26-Jul-17 10:18:53
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Re: iTunes sound quality is officially not quite as pants


[re: billford] [link to this post]
 
In reply to a post by billford:
But as an easy first shot, have you tried deleting the iTunes preference files?
Bingo! We have a winner laugh

I can't see any particular setting in the old preferences file which would obviously caise sound degradation but it has 59 items in its root whereas the new file has just 15.

Thank you.

Sarah

--
If I can't drink my bowl of coffee three times daily, then in my torment, I will shrivel up like a piece of roast goat

Spiders on coffee - Badass spiders on drugs
Standard User billford
(elder) Wed 26-Jul-17 10:45:11
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Re: iTunes sound quality is officially not quite as pants


[re: caffn8me] [link to this post]
 
In reply to a post by caffn8me:
Bingo! We have a winner laugh
Glad to hear it smile

I've always been wary of preference files ever since I had a weirdie which (I think) was caused by something like the preferences editor only showing/setting the bottom 4 bits of a byte (leaving the others unchanged), but the app used all 8 without masking out the bits it didn't need. So when something, somehow, set one (or more) of the high bits it didn't show in preferences, but the app did some very peculiar things crazy

Bill
A level playing field is level in both directions.

_______________________________________Planes and Boats and ... ______________BQMs: IPv4 IPv6
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