Part 2 - Making Your Computer an Audiophile-Quality Music Player

HOW TO GET THE BEST SOUND QUALITY FROM ITUNES

Now that you know from Part 1 how to import or purchase full quality audio files, the next step is to get the best sound from the basic iTunes app itself. There are settings in iTunes that will degrade the playback quality and should be defeated when you want totally accurate sound. It's O.K. to use them for casual listening, parties etc. if that works best, but this is what to do when you want to hear things right. When all of these steps are followed, iTunes is actually a bit-perfect 16 or 24 bit digital audio player. These steps apply to Mac computers. It is much more difficult to get bit perfect audio from a PC. You need to do these 4 steps and more. For that I'd suggest a google search.

THIS IS WHAT TO DO IF YOU'RE ONLY INTERESTED IN PLAYING CD-QUALITY AUDIO FILES (44.1K/16 BIT)

Most music lovers will be more than satisfied with CD-quality once they rip their CD collection properly or begin purchasing 44.1k/16 bit downloads. These 4 easy steps cover what to do so iTunes itself isn't affecting the sound quality. If you're interested in high-definition audio (48k, 88.2k or 96k/24 bit), you have to do these four plus step 5.

STEP 1 - Launch iTunes, open preferences and select 'Playback' at the top. Make sure 'Sound Enhancer' and 'Sound Check' are NOT turned on, then click 'OK'. The 'Crossfade' feature will not hurt anything if you like it.

STEP 2 - Under the 'Window' pulldown menu at the top of iTunes select 'Equalizer'. Uncheck it, and to be safe set the Preset menu to 'Flat', then close the window.

STEP 3 - At the top of the iTunes screen, set the volume control all the way to the right. If you are feeding the computer's analog audio output jack to your hi-fi system or powered speakers, the computer's volume control should also be all the way up. You should adjust the volume from your system or speakers, not iTunes or the computer. If you're listening on headphones from the computer's headphone jack, or if your powered speakers don't have volume controls, use the computer's volume control, not the iTunes volume control.

STEP 4 - To complicate things, you can also adjust volumes per song or per album. If you have never done this, don't worry about it, there's nothing to undo. If you have made volume adjustments to individual songs or albums, do this: Highlight an album on which you've made volume adjustments and 'Get Info'. You'll be asked if you want to edit multiple songs, click 'Yes', then click 'Options' at the top of the info window. You'll see a slider for volume adjustment. Leave it set at 'None' and check it, then click O.K. All of the songs on the album will be reset for no volume adjustment.

That's it for regular CD-quality audio files. Proceed to Step 5 if you're interested in playing high-definition audio files (48k, 88.2k or 96k/24 bit AIFF, WAV or Apple Lossless).

STEP 5 - Even if you knew that iTunes can play high-definition 24 bit files up to 96khz, there's something devious going on under the hood that you may not be aware of. When you are listening to any audio media player like iTunes, you are listening to an 'audio engine'. iTunes manages your music library, and provides the DSP functions we defeated in steps 1 - 4. But in Mac computers, the audio engine you are listening to is the QuickTime player. The little secret to this is, you need to set QuickTime's sample rate to match the sample rate of the file you're playing. The default setting is 44.1k, the standard rate for CD-quality files. And that's why you don't need to mess with this if all you'll be playing is 44.1k/16 bit files. But if you play an audio file with a sample rate that does not mot match QuickTime's setting, QuickTime does a rather awful internal sample rate conversion to whatever rate it is set for. So if you don't know how to do this, the extra money you spent for 96/24 downloads was wasted - it will sound worse than the same song as an mp3 if Quick Time is sample rate converting it. Here's how to set QuickTime's sample rate:

In your utilities folder launch the "Audio MIDI Setup" app. Highlight 'Built-In Output'. On the right you'll see pulldown menus for setting sample rate and bit depth. Set the sample rate to match the audio files you're about to play and bit depth to 24 bit. When you go back to playing 44.1k/16 bit lossless or mp3/AAC's, it's still recommended to leave the bit rate at 24 bit. As a side note, any mp3 or AAC that you've purchased will be 44.1k. They can be 48k, but that is very rare.

The following screen captures show how good - and bad - iTunes can be depending on preferences and QuickTime settings:

A 48k 24-bit 10kHz sine wave played through iTunes with QuickTime sample rate set to 48k and bit depth to 24 bit, iTunes DSP defeated and volume control at 100%. The tone shows as a pure spike at 10kHz with no artifacts around it. This is a bit-accurate reproduction of the tone.

A 48k, 24-bit 10 kHz sine wave played through iTunes with QuickTime set to 44.1k, 16 bit. All audio energy outside of 10 kHz is due to distortion caused by the QuickTime sample rate conversion and truncation. 

IF YOU WANT THE DETAILS, HERE'S WHY YOU DEFEATED THE FUNCTIONS IN STEPS 1 - 4
Each feature we disabled is a DSP, or Digital Signal Processor. Each of these will degrade the signal quality to one degree or another. The worst offender is 'Sound Enhancer', which is a pretty awful 'spacial expander'. This makes the music sound as though it is coming from outside of the L/R speakers, creating a much larger sound field. Even though it may wow you when you first hear it, it is highly distorted and not at all accurate.

The EQ is the second worst offender. Even quality eq's add phase distortion, and this is not a quality eq. If you have a decent hi-fi system, especially if it's a good analog preamp or receiver, its eq should be much better.

The master volume control, individual song/album volumes and the Sound Check feature degrade the signal the least. But even bringing the master volume down the smallest amount will cause a digital distortion called 'truncation distortion'. This will be most noticeable on mp3's or AAC's, a little less so on 16 bit lossless or lossless-compression audio files, and barely perceptible on 24 bit files. If you want to use the individual song or album volume adjustments, you should still leave the master volume all the way up; a combination of the two will degrade the audio much worse than using only one.

The Sound Check feature is a rather clumsy attempt at matching the volumes of songs between older vintage CDs and newer ones. Any music produced or remastered after 1995 is usually much louder than music released prior to that. This shouldn't matter if you're sitting down to listen critically to an album, just turn it up as loud as you want. But for parties or casual shuffle-play listening it ca be distracting, so that's a good time to use the feature. You'll soon be hearing of a much more accurate method of matching 'perceived' volumes.

That's all for Part 2. Part 3 will address how to improve the quality of your digital-to-analog convertor over what is built into the computer, which is where we really start getting into the audiophile side of things.