October 01, 2011

Signal Transmission (or: Why You Should Never Buy Monster Cables)

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I spent last night drumming, so you fanciful folks get a simple article this week.

Do You Buy Hardware Cables?

Have you ever wondered why, whenever you go to a big box retailer like Best Buy or Circuit City, the prices you see for simple cables can extend upwards of $40, and sometimes more? Sure, the packaging talks about gold-plated terminators and being twelve times faster than the competition, but does that really justify the price difference? I'm here to help you learn a bit and potentially (hopefully!) save a great deal of money.

History Lesson

In order to do that, I'll have to tell you a little bit about what those cables are actually doing. In order to give you a good grasp of the situation, we'll need to go back to the difference between analog and digital signal transmission. Any time you want to transfer information between two pieces of hardware, you're going to need some variety of wire or connector. It used to be the case that we'd just stretch copper wires between them, letting the hardware pretend that it was just a really long internal connection. This is actually how most speakers in home theaters and car sound systems are wired today: just take some copper cables, connect them to the right terminals, and the speakers take the actual electrical impulses from your player to reproduce the sound. This is what analog is.

Digital signals, on the other hand, are more complicated in their execution (but not conceptually difficult). When one piece of hardware, for instance a DVD player, wants to communicate to a visual display, say a television, the DVD player starts off with the raw data it's trying to display. How the data starts off (zeroes and ones on a DVD, magnetic charges on a tape, a ceramic disc with grooves) doesn't really matter. That data needs to be in a format that the television can understand, so there's hardware inside of your DVD player to turn the input (whatever it was) into something the TV can understand. Then you use a cable to transmit that digital signal to the television, where it's converted using dedicated hardware into the picture that you see.

The Difference

Long, boring, blah blah blah. Why's all that important? Well, it turns out that analog and digital signals have a major, critical difference. When analog signal is degraded or weakened, you start getting interference with your output. If you accidentally drive a staple through a cable wire (the horror stories from working as support at Time Warner are deep and many) but you don't use a cable box, you'll still probably be able to see a picture on your screen, but it'll have all sorts of white flecks or static in it, and your audio will hiss, and all sorts of other terrible things. However, if you take that same exact pierced cable, and run it through a cable box (which turns the analog signal from the cable wire to a digital one (technically your TV did that with the cable wire itself, but don't worry about that)), you'll be lucky to get a picture a quarter of the time, and weird green boxes, a black screen, and no audio the rest.

You see, with analog transmission, you never have a perfect signal (there's always some variety of signal loss when transmitting analog signal), but it's pretty resilient in handling information loss (stapling the wire). With digital transmission, though, it's generally an all-or-nothing situation. I say generally because in most cases, the manufacturers of hardware try to deal with information loss, but it's must harder to get right than just accepting issues like analog does. In the earlier example that involved a cable box, the same staple that gives you some static with analog can completely stop you from getting your shows with digital.

Why We Use Digital Transmission

With that in mind, why do we use digital at all? Well, the normal situation for folks is that the hardware and the wires are fine, in which case digital give you perfect signal reproduction when you'd always have loss with analog. The much cooler thing is that digital information uses much, much less bandwidth (or how much data can go across a wire at a time) than analog. Analog is kind of a brute-force solution, where a single type of information is pushed across while trying to keep it as close to the source as possible. Digital uses zeroes and ones to transmit the information perfectly, and it's much easier to cram zeroes and ones together while still getting them to represent the same thing. When you're able to push more data, you can have more colors, more pixels, more channels, more everything!

The Take-Away

Alright, that lesson's over and done with. Now I'm able to tell you why it matters! Digital allows you to transmit data flawlessly, so long as you meet a minimum of bandwidth and don't have too many problems with the cable or hardware. The people who make the specifications for this are really good at what they do (usually a consortium for each specification, made of several companies that have a vested interest in getting it right (among other things)), and they leave a lot of breathing room in specifications for growth and failure. So long as you meet the minimums they provide, things just work.

Why are Monster Cables and their ever-present ilk evil? They attempt to con potential customers into believing that gold-plated terminals, or super-precise build standards, or potential transmission speed, or the dead chicken they have glued to the ceiling of the factory actually matter. Here is what's actually important when buying a cable:
  • make sure it's the type you need for your hardware
  • it must meet the minimum specification
  • it should probably be certified (differs per cable, but not as important as you think)
  • it should be long enough for what you're using it for
That's it. In other words, the wire could be made of tin and the terminals made out of rubber, but so long as it meets the specification, it will work.

Extra Special Bonus Round

If you're still with me, I've got an awesome gift for you for toughing it out. If you need cables, order them online. Those $60 HDMI cables you see at Best Buy? It turns out they cost less than $10 from reputable dealers. It can go as low as $5 if you wait around for sales. Here's a link for one right now! Pretty sweet, eh?
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