The computer has always been the basis of digital audio streaming, the least expensive way to dip a toe is to connect a laptop to a DAC via a length of USB cable. This approach is dubbed the ‘push’ approach because the computer sends the signal to the converter, a streamer on the other hand ‘pulls’ the data from the source, usually a NAS drive. Using a computer has the advantage of flexibility in the choice of playback software and cost but to get decent sound quality you need a dedicated computer that has been built with this purpose in mind, which tends to undermine the cheapness factor. In most instances you need direct access to the computer to control playback but software such as JRiver Media Center can be controlled with an app on a tablet. The only other limitation is that USB leads do not perform quite so well if they are over a metre or two long.
A streamer or renderer on the other hand is built from the ground up as an audio component, therefore attention is paid to keeping out RFI through the use of linear power supplies and minimising jitter and the other ills of digital audio that the computer world is not bothered about. Streamers connect to the network where they can pull audio data from a media server, generally a network attached hard drive or NAS with an operating system such as Twonky media onboard. Companies including Naim and more recently Melco offer higher quality servers that can also rip CDs and offer alternative connections alongside the RJ45 socket required for connection to a network wired with Ethernet cable. For best results and high resolution formats a network should be wired rather than wireless, but as Sonos has proved wireless networks are good enough for many.
Another school of thought is to have the music stored on the player itself, eliminating the need for separate music storage, this is what happens in a Naim HDX and a variety of both high and budget end products. It simplifies initial set up at the cost of flexibility. But it does mean that the network is only necessary for control and grabbing metadata so can be wireless without sonic compromise.
The network approach means that the media server or storage device need not be in the same room as the player, and as NAS drives are not the quietest things this is quite handy. It also means that multiple players can share the same drive, both wired and wirelessly. One of the nice things about having your music on a network is that any streaming device can access it, in my case that means the iPod Touch that plugs into the kitchen radio, but it could just as easily be a smartphone. And while you need a tablet or smartphone to use the control app for a dedicated streamer, that same handheld device can be both controller and player. Therein lies the rub of course, if you leave the iPad in the kitchen it won’t be on the sofa when you want to choose an album or playlist on the main system.
The playlist is another aspect of streaming that is very popular, essentially it’s a means of collecting a selection of tracks in a list that can be saved. It’s a bit like a compilation tape but a lot more flexible as you can have almost as many tracks as you like and you can have the same track on as many playlists as you want. As an old school album listener this is not something I have adapted to in truth, I tend to play tracks or albums but rarely get around to building playlists despite the ease with which it can be achieved. But I get the impression I am in the minority in this regard.