I promised a simple, quick and dirty explanation of music streaming for those with no experience in this area. So here goes...
STREAMING SIMPLIFIED TO THE MAX
While one could certainly write a book about music streaming, a broad overview does not have to be that involved.
In order to reproduce digital music, there are a few components critical to the task. They are 1) a music source; 2) a digital to analog converter; and, 3) downstream reproduction equipment.
When you play a CD, the physical CD is the source and it contains the digital music files. CD players typically have an internal digital to analog converter (DAC) that converts the digital stream to analog and feeds the result to the downstream equipment (preamp, amp, etc.).
When thinking about a streaming music system, the same components apply. Rather than a physical CD, the music files are stored on some other digital device. This could be a computer, a network storage device (NAS), a USB backup drive or on a hard drive in the streaming player itself.
The streaming player simply accesses the files from where ever they are stored, un-compresses them if necessary and passes them along to a dedicated DAC for processing. The analog output of the DAC is then passed to the downstream gear.
MUSIC FILES
Where do the digital music files come from? There are several potential sources. You can use a Windows computer program like dBPoweramp (the best) to "rip" your CD's into digital music files and store them on a computer, NAS or, if it is available, a hard drive on the streaming player. MAC and Linux based computers also have applications available to do this task.
Another option is to download music files from any one of a number of web sites offering music files for sale. One big advantage to downloading music is that it is often available in higher resolutions than a typical CD. CD data is stored in 16 bits sampled at a rate of 44.1kHz. (Every 44.1 thousandths of a second, the music stream is sampled and stored as a 16-bit binary number).
But rather than being limited to 16/44, you can download files with greater bit depths (more resolution) and higher sampling rates (more closely approximating analog quality). 24/96 files are quite common as are resolutions up to 24/192.
A few years back, Sony introduced a new CD format called SACD, which boasts even higher resolutions. Anti-piracy was one key feature of SACD's. This was important to the music industry since SACD recordings were closer to (or an exact match of) the original master recording. This makes SACD's relatively difficult to rip. But you can now download many DSD files, which is the format used in SACD's. In fact, many of the files you can download were recorded in DSD to begin with and you are actually downloading a bit-for-bit copy of the original master recording. So you are not getting a down-rez'd version of the recording, but a copy of the original recording itself.
COMPRESSION
Naturally, the higher the resolution, the larger the digital files become. So in order to conserve storage space, file compression comes into play.
By now, you are probably familiar with MP3's. The MP3 format was developed some time ago to cope with slow internet download speeds and the lack of significant storage on early playback devices like Apple iPods. The MP3 format results in the smallest possible file sizes. The problem is, MP3 is a "lossy" compression algorithm. Small file sizes are realized by throwing information away. And once it is thrown away, it can never be recovered. In a real sense, MP3's were the first "advance" in sound reproduction that was actually a giant step backwards. It was needed at the time, but it is far from ideal.
Fortunately, there are a number of very good "loss-less" compression algorithms available. FLAC is one such algorithm. It can reduce the size of the music file to about half, but when the file is played it is expanded to its original form, bit-for-bit. So storage requirements are minimized without any performance penalty.
CD ripping programs handle this compression automatically and streaming players un-compress on the fly. So, as a user, you do not need to be concerned with this aspect of streaming music beyond selecting the format you want your files stored in.
A SIMPLE STREAMING SYSTEM
You probably already have a streaming system but didn't realize it. If you own a MAC, you already have iTunes. If you have a Windows computer, you probably have Windows Media Player or may have installed an alternative like Winamp.
Basically, these systems allow you to store and play music on your computer and represent a simple music streaming system. They process a library of music files, have an interface that allows you to select tracks and control play, and pass the result to a built-in DAC (the audio card) in your computer.
But these systems have limitations.
First, you may not want to have a dedicated, noisy computer in your listening room. You don't want to be saddled with using a monitor, keyboard and mouse when using your system. And you don't want to be limited to the resolution of the music you are listening to (primarily 16/44).
That is where higher-end systems come into play.
A MORE SOPHISTICATED APPROACH
To set up an audiophile music streaming system, you basically need the same things we started with in the very beginning: 1) a storage device; 2) a streaming device with appropriate controls; and 3) a high quality DAC. So let's take a look at each of the three.
STORAGE DEVICE
As mentioned above, music files can be stored on a variety of devices. These include a computer (can be an older computer placed in another room and connected to your router), a NAS (dedicated network storage device), an inexpensive USB backup drive connected to your computer or your router, or a hard drive (regular or solid state) built into your streaming device.
Keep in mind that the size of your storage device will depend on the number of recordings you want to store and the resolution of those recordings. Using flac, you can probably store 500 Redbook (16/44) CDs or more on a 500GB drive. Higher resolutions will require more disk space. If you start with 1TB or 2TB, you'll have plenty of room to grow your music collection before having to increase your storage. By that time, higher capacity drives will be available at lower and lower cost.
Again, for the most part, it makes little difference where you store your music as long as you are able to share the location over your network. That said, if music is not stored on the player itself, you will be involved in networking to some extent and that can make configuration a little more difficult.
THE DAC
As indicated above, your CD player has a built-in DAC. So does your computer. But both of these are somewhat limited compared to outboard DACs that one would employ in an audiophile streaming system.
There are a wide variety of outboard DACs on the market today. They range from simple 16/44 DACs that will allow you to play CD quality (Redbook) files, to high end DACs that can handle the highest resolution DSD files.
The higher you go in resolution, the more complicated things become. For example, any USB streaming system built around the Windows platform will need special drivers for resolutions over 24/96. This is because Windows USB systems were not designed to handle the higher throughput required (MAC and Linux systems do not suffer these limitations).
As long as your DAC can handle 24/96, you will have no problem using it with any type of streaming device without having to resort to special drivers.
Above 24/96, things get a little more complicated. USB Class 2.0 Audio 2.0 is a digital format that defines how one can implement a USB system in a DAC. Manufacturers can use it or can define their own standard. If the DAC is truly USB Class 2.0 Audio compliant, it will work as a plug-and-play device in any MAC or Linux-based system. (Windows computers will still need special drivers as mentioned above.) DACs that are not USB Class 2.0 Audio compliant may require proprietary drivers no matter what platform the streaming player is built on.
Fortunately, many higher end DACs these days are USB Class 2.0 Audio compliant. And if you make sure yours is, you should not have an issue. While other DACs will work fine with the manufacturer’s supplied drivers, I do not personally like this approach. I have a lot of older recording equipment that is in great shape. Unfortunately, all the drivers are for Windows XP which is no longer going to be supported. So as I upgrade my computer system, I can no longer use this equipment since there are no upgraded drivers available. Manufacturers simply can't afford to build new drivers for older equipment every time operating systems go through a major upgrade and the older drivers no longer work. So "buyer beware."
THE PLAYER
This is where things get somewhat more complicated. Keep in mind here that no matter what you use as a streaming player, you are using a computer of some sort. Many commercial products are designed to run on embedded processors. Rather than full blown computers, these do not have video circuitry to drive a monitor and do not normally have the capacity to use keyboards or mice. But they are still computers.
The job of the player is really quite simple. It has to perform three functions:
1) Access and manipulate audio files stored internally or somewhere else on your network.
2) After processing (un-compressing), send the music stream to your DAC.
3) Provide some sort of interface to control selection and playback, normally in addition to many other functions that become available on a system of this type. These added functions can include things like volume control, the development and storage of playlists and the display of information regarding the audio file being played (artist, genre, recording date, etc.).
These functions can be done by just about any computer or computing device with the appropriate software installed. iTunes or Amara are examples of software running on a MAC. jRiver is a popular Windows app that is also being made available for MAC and Linux devices. MPD is one of the most mature and robust solutions running on Linux.
For me personally, the user interface is one of the most important considerations in choosing a platform. As I mentioned above, I don't want to be forced to use a computer, a monitor, a mouse and a keyboard to get the most out of my system. So, in my case, the availability of an iPad remote control application was important.
When I began my search for the "perfect" player (perfect for me anyway), I was not able to find exactly what I was looking for. I had used a Slim Devices Squeezebox for a while, but it required a dedicated server to be running on a networked computer (the server was a little buggy and not always stable). And it was limited to 24/96 at the time. jRiver was a great app, but required a full-blown Windows computer. Amara was the rage, but required a MAC computer. And only the Squeezebox had an iPad interface that I felt I could live with.
Since I couldn't find what I wanted, I decided to build my own. What I ended up with became the StreamPlayer, a product that we do not promote, but do build for some customers who want the same thing I wanted.
It is currently based on a small embedded processor with enough power to do the job at hand. (I say currently because I am always playing with alternative hardware platforms.) While it is a computer, it is silent, with no noisy fans required by most full-blown computers.
It runs a stripped down version of linux, a very stable and crash-resistant operating system. It uses an app called MPD as the player. This too, is a limited application that does the very simple jobs at hand in a very reliable fashion. The music files themselves can be stored and accessed externally, no matter where they are on the network, or stored on an internal drive (solid state or regular).
The system can be controlled by a wide range of applications that run on computers, Android phones, the iPod Touch, an iPhone or an iPad. You can even have a number of these remote control apps running at the same time and when you switch tracks on one, the results will show up on all the others.
While there is certainly a world of possible streaming system set-ups, this is the one that I find the most usable (and I have used them all).
Right now, I use a StreamPlayer with a 2TB internal drive that holds all my music files. It is connected via Ethernet to my internal network. It streams music via USB to one of any number of USB DACs that I own. I control it with an iPad via a wireless connection using an app called mPad.
With this system, I have access to all my music at my fingertips. I can create and store playlists. I can (although I do not often) listen to internet radio stations and use last.fm to stream music from the internet. I can look up music by artist, album, genre, year, etc. I can search for a song by its title.
When we started building StreamPlayers for others, I realized that since it was Linux based, it would perhaps be a bit too technical for non-computer-savvy individuals. So I spent about 8 months developing a web-based front end for it. The web pages help a user configure things and the pages then write all the Linux configuration files required to make the necessary system changes. In addition, the web interface includes a player, tools to examine system performance and links to free web apps that can help users get the most out of the system.
When you have a system like this, it will totally change the way you listen to music. With LP's or CD's, you listen to one artist for a period of time and the order the songs are not under your control. Once you have a streaming system set up, you move from one track to the next, from one performer to the next, build a queue, re-order it, etc. This may not sound like much of a sea change, but believe me, it is.
To be honest, I developed my system to make it easier to access selected tracks on the fly at audio shows. But I would now never go without it.
Well, I hope this helps the uninitiated. It by no means was meant to be an in-depth discussion of the topic at hand. That would take an entire book or perhaps more. But it should provide a starting place if you have never looked into music streaming in the past.
- Jim
