So I figured with the digital audio section and more people wanting to explore this realm of audio I'd make an attempt at a very brief starter guide. This is not intended to be an exhaustive 'how-to' but rather an overview that's intended to help someone new to get an idea of what's involved. The objective isn't to teach you everything you need to know, but to get you started. At the conclusion you likely won't have all the answers but you'll at least know which questions to ask. I'm trying to keep opinion out of this and keep it to just what I believe are industry agreed upon facts.
I'll start by clarifying, by 'digital audio' I mean playing audio files from a computer or similar device on an audio system. CDs are technically a form of digital audio, but that's not what we're after here, we're talking about playing digital audio files from a library or file system. This world is easily broken into two main areas of equal importance: Creating your digital files and Playing back your digital files. I'm going to cover each of those separately
Creating your Digital Audio files - Rip, Tag, Organize
There are two basic types of digital audio files, compressed and lossless. There are multiple variations of each, but everything falls into one of the two buckets. For an ideal listening experience you'll want to have a library of lossless audio. Some people will argue that you can't hear the difference between a 320kbps compressed file and a lossless file, but general conventional wisdom is that many people with good enough systems and ears can hear a difference. Hard drive space is cheap enough these days that it just makes sense to rip to lossless.
There are basically two ways to get digital audio on to your computer: you can rip it yourself from your CD collection and/or buy it from an online service like HDTracks. Note that using a service like iTunes isn't ideal if you want lossless audio because their music collection is compressed. I've never given iTunes a dime of my money. There are services like HDTracks that do sell lossless files (and even some higher than CD resolution lossless files). Either way, your music comes in via one of these two methods. My collection consists of a lot of each.
The goal when ripping is to end up with an accurate bit for bit rip of your CD. The first thing you'll need to do is decide on the software you'd like to use to rip your CDs. There are LOTS of options out there that will vary slightly depending if you're on PC or Mac, but they all do essentially the same thing. My product of choose is dbPowerAmp because it has a system in tact that helps ensure that you get an accurate, bt for bit, rip of your CD. It's not the only option, and the purpose here isn't to sell you on dbPowerAmp, so you can do your research and determine what works best for you. Just make sure you end up with something that can give you bit perfect rips.
The next thing is to make sure that your music is tagged properly. Most software and hardware playback solutions work on the concept of a music library, where your library software uses tags that are stored in the media files themselves to organize by things such as genre, artist, and album. The easiest way is to typically tag the files the way you want them as you rip them. I personally use a non-conventional method where I rip my music into a given folder structure and then use software to create the tags based on that folder structure, but most people prefer to let the software manage the tags. Either way, the goal is to use a consistent tagging structure and get your tags the way you want them.
So now you've got your music ripped and tagged, all you need now is a method of actually playing back the files.
Playing your digital audio files
When playing back audio, the goal is to get that bit perfect files that you ripped or downloaded all the way to your preamp or receiver with as little alteration to the original file as possible. There are countless permutations of how playing back a file can be accomplished, but again they fall into two categories: connecting your computer directly to your audio system and using the computer or a remote control app to play back the files OR using a device that sits on the same network as your computer and can stream (wirelessly or wired) audio files. I'll briefly discuss the two:
The first option basically consists of 9for example I can control iTunes on any of my Macs from any of myou somehow hooking up your computer to your audio system and using either the computer itself or a remote control app on maybe a tablet or smartphone to control the audio player on your computer (for example I can control iTunes on any of my Macs using my phone or iPad). This tends to be the cheapest initial option as you can do something like hook up an optical cable directly from your computer to your receiver. However, there are lots of variables like random quality of the digital output on different computers, the need to bypass the system audio mixers on both Windows and Mac, asynchronous USB, etc etc. So this option CAN be cheaper, but it can also get more complex if you really want to do it right.
The other option is to use a device that streams the music from your computer. The two most common examples are the Sonos players and the Squeezebox players. Each work differently but have the same basic function - they stream files wirelessly or wired from your computer or network drive into themselves and output audio into your receiver or preamp. These are a simpler approach because they bypass a lot of the potential issues you can run into with outputting directly like a computer (all those I listed above). The only downside here is expense. They're not incredibly expensive but are an additional cost. These often sound better than a poorly implemented computer output rig, and can sound as good is an expertly implemented one.
I suppose I can't have a digital audio section without at least mentioning DACs. Regardless of which path you choose, you'll also likely want to get an external DAC as well, although which one you get may be defined by which approach you take. There are computer sound cards that have good DACs on board and can potentially output very good sound, and there are streaming devices that also have good DACs inside (I'm particularly fond of the DAC section in my Squeezebox Touch). Remember, the DAC turns a digital signal into an analog one, so digital cable (coax, optical, USB) goes into your DAC, two analog RCA cables comes out and into your preamp or receiver.
So there you have it. Like i said, not a really thorough guide, just a very brief intro for someone thinking about jumping in to the world of digital audio.
Enjoy the music!