OK, you finally have all of your music on your computer, including the 96kHz/24 bit files you bought online and a superb new DAC such as the Bel Canto DAC3. Now to get your computer outputting the best possible sound.

Apple's iTunes has since version 7, made great improvements for both Mac and Windows platforms. The sample-rate conversion (SRC), word-length handling, and volume control are all significantly improved. If you take the time to setup iTunes properly with the correct system settings applied, iTunes can provide very high quality playback for resolutions right up to 24-bit, 96 kHz.

The very first thing you need to do is to turn OFF the 'Crossfade Songs', 'Sound Enhancer' and 'Sound Check' options in the iTunes preferences. It should be obvious, but for quality sound playback you must be using a non-compressed format such as AIFF or at the very least, a lossless format such as Apple Lossless.

Sample-rate conversion is where many of the problems occurred in iTunes, however since version 7 SRC has been greatly improved and in fact, is of such quality that it is totally transparent in operation. iTunes also now provides a high-quality, 24-bit dithered volume control which is a significant improvement when compared to the non-dithered 16-bit control in older versions. However, I still prefer to use the volume on my amplifier and leave iTunes at full output.

The main problem with iTunes is it's inability to change sample rates to match the audio it is playing. In a perfect world iTunes should simply change sample rates as needed to match the file being played but this is not the case. Instead, if you are playing a 48kHz file and your system is set to run 44.1kHz, then the SRC of iTunes kicks in. Now while the SRC is very good, it is an unnecessary overhead on your CPU. This is not really a problem if you have an 8 Core Mac Pro, but if you are running a Mac Mini, it may well be.

We could simply let the OSX CoreAudio take care of SRC, but it is of poor quality when compared to the SRC built into iTunes these days so it is to be avoided! Equally, the SRC built into Windows 2000 and XP are also of low quality, Vista however sports a much better SRC.

So, what do we do to get the best out of our systems?
The principals are simple, avoid your operating system using it's built in SRC and get iTunes to do all SRC duties. To achieve this, you need to set your system to run at 96kHz/24 Bit, and set it prior to launching iTunes.

After you launch iTunes it will adopt the systems sample rate and output all music at 96kHz/24 bit using it's built in sample rate converter. Now when your music is playing back at random, a 44.1kHz file will be converted to 96kHz, a 48kHz file also, and a 96kHz file passed straight through.

If you fail to do this setup, the expensive 96kHz/24bit files you purchased will be down sampled to whatever your system is normally running at, which in most cases is 44.1kHz. Happy listening!

An alternative setup
According to the Sonic Studio web site, the AMARRA COMPUTER MUSIC PLAYER, is the audiophile quality computer music player for the most discriminating enthusiast. Amarra represents the next generation of computer based music players and is designed using the same technology in use today by record companies worldwide for producing CDs and DVDs.

Amarra (for Mac OSX only) uses advanced mathematical algorithms, optimized data handling and processing, advanced software based Sonic Equalisation, integrated gain structure and TPDF dither processing and most notably, Automatic hardware sample rate adjustment to weave it's magic.

Operating as a plug in to iTunes, Amarra claims to offer improved audio quality when playing back un-compressed audio, other compressed formats bypass Amarra and play directly out of iTunes. Having tested this software I can say it does what it claims in terms of hardware sample rate switching, it works a treat.

However I could not really test it's claims of improved sound quality as I do not have one of the listed DAC's it is compatible with, nor do i fully understand the need for a compatible DAC, but for those who do have setups that are a match, this may be a good thing to try. If you do, let us know!