External HD Changing the quality of the sound?

BitPerfect is an app that works alongside iTunes. You use iTunes to manage your library (set which HDD to keep the library in etc, add new songs, add metadata info if needed, create playlists etc).

BitPerfect just takes over the playback engine from iTunes. You install it from the App Store like with most new apps. It will be in the Applications folder.

a. Use a SSD for the main OS
b. OK to use an external drive for music
c. use a music player software that does memory cache-ing

Oh, if you are using a USB connection on your DAC, use a FW or Thunderbolt drive. If you are using a FW-SPDIF connection, use a USB DAC.

I too use iTunes. But the Mac version is better integrated with the OS from what I understand than the PC version and it is a great way to organize album meta data and playlist. I just organize them once and it works for my music servers and iOS/iPod devices as well.

To use memory play, try BitPerfect from the AppStore. It's a very simple, very easy to use plug in to iTunes. It bypasses iTunes' playback engine and sounds very good.

It's IMHO a close second to Audirvana Plus (which is still affordable) and A+ provides the option to play DSD files as well, if supported by the DAC (it will convert DSD to PCM otherwise). If you only have primarily RBCD or HR PCM, BitPerfect will work just as well.

PureMusic and Amarra IMHO are much pricier and not worth the added moolah.

Yeap. BitPerfect (click on the little logo on the top right of the menu bar. Select Preferences. You can adjust the size of the cache obviously limited by the RAM installed but RAM is cheap these days. Our old 2011 iMac already had 4x4GB RAM

Ah, Ghosthouse. I get what you mean. BitPerfect just needs to know where iTunes keeps the music files the first time it loads up. The main options are just listed in the drop down menu.

If your DAC displays the sample rate, there is one way to check if it is running, Play some music files in 44.1 and in 96kHz. Without BP enabled, iTunes would resample everything to whatever you set in AudioMIDI setup for the audio device.

So if it is set to 96kHz, even yr 44.1kHz music would be resampled. With BitPerfect set to native mode, it would switch between different sample rates depending on which file you are playing.

I find that my EMM Labs XDS1 and Playback Designs still sound better with a spinning disc but the software keeps sounding better so I suspect it might overtake it eventually.