Telephones, CD players and frogs
Yesterday we began our look at networked audio - connecting a DAC to your computer through a network rather than a fixed length USB cable (or S/PDIF cable). The advantages to connecting over a network are many, including the ability to put your DAC anywhere you wish and the possibility of as many DACS as you like throughout your home. Sending cover art and song titles to your DAC an added bonus. We also learned that almost all of us already have a home network setup even if we didn't know that. All you need to create a home network is a simple router - which you probably already have. Today let's get a little learnin' under our belts about the fundamentals of sending audio over a network. Remembering back to our discussions on how a CD transport works when connected to a DAC - that of sending a directly connected stream of bits between the two machines - we need to understand this no longer happens when we get computers involved. To understand this we'll go back in history a little. When I was growing up the phone system was very different than it is today. At our home we had what was known as a party line which meant we shared the telephone resources with two of our neighbors. This arrangement worked out well until my two sisters became teenagers and would spend hours chatting with their girlfriends - and our neighbors had to ask them to get off the phone to use it themselves. If we wanted to call someone long distance we had to first call the operator who would then place the call for us. Direct dialing outside our city was simply not possible at that time. Even the dialing itself was different than today, using a rotary dial that simply hung up the phone multiple times to represent different numbers: 6 hangups meant the number 6 and so on. This system relied on the fact that when we called someone there was a direct connection to the other person's phone over a single pair of wires - despite the fact we were shuffled through numerous switches or an operator - once a connection was made between two parties there was one dedicated stream on one wire between the two phones - much like the dedicated stream between a CD transport and your DAC. Then one day all this changed when the phone company announced a radical new system that used push buttons and tones to dial and, much to our delight, our own "private" line and the ability to call outside our city without the aid of an operator. Man, that was a big deal back then. So, what changed? The phone company went from a direct single connect method (one wire needed for each call) to a shared many connected method (many calls over one wire at the same time) that gave us the impression it was private - when actually we shared it with even more neighbors than before but we didn't know they were there. The phone company built a network where many things happened on the same wire at the same time. Now let's return to our present day discussion and understand that computers and networks have the same challenges in common with the phone system: many things must travel the same path at the same time. Computers must respect the credo: "share the road". Tomorrow we'll learn about packets which are the little devils that both USB and network audio break the music into and send them scurrying about. Keeping these millions of little bits of music marching in the same direction and not getting mixed up with other travelers on the same road is akin to trying to keep a wheelbarrow full of frogs from jumping out - but it all happens because of a common language everyone understands - including the frogs in the wheelbarrow.
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