Dr. Geek: Cables

A short discussion with Hanne today about a Firewire cable she needs struck me with a Geek-Lore detail that may not be widely known, so I thought I could share. Before I get you into the weeds, the actual conversation I had with Hanne went approximately like this:

H: I need a Firewire cable but I don’t know exactly what I need.

M: What kinds of connectors are we talking about? The pointy Firewire connector and a square one?

H: Yes, but I don’t want to order the wrong thing.

M: I know you don’t, but likely you want one of these.

H: But are you sure about the pins?

M: Short version is that the number of pins is just a short or synonymous name for the type of connector and not indicative of the number of actual connections involved. I’ll write a blog post! But then this evening we can look at the specs together and be double-sure.

To whit:

Key things to know about cables in general:

  • Cable sellers generally will sell their wares at whatever the specific market they sell in will bear. Some cable sellers (like Monster) have gotten away with charging ruinous prices for cable features that don’t help anyone buying or using the cable simply because they’re selling in the audiophile/videophile market where consumers are used to paying a lot of money for high-fidelity.
  • Most computer-oriented cables you buy are digital. Digital signals are on-off and except in really adverse conditions (like, for instance, in the middle of a solar flare on Mercury or operating on the surface of Venus), signal fidelity in digital signal transmission has no bearing on the overall result. This is why I made the remarks I did about Monster, who sell gold plated HDMI cables as if they will somehow work better than non-plated HDMI cables. More info here at CNet (about HDMI cables).
  • When talking about non-network cables, most descriptive language about them on merchant web sites will mention what kind of connectors the cable has (e.g. “USB A to USB B” or “Firewire 6 pin to Firewire 9 pin“). Pay attention to these sorts of designations. They’re important to identifying the kinds of connectors you’re paying for. If you’re stuck, look at the same cables for different vendors (Deep Surplus, Newegg, Monoprice, Cable Train) to get a sense of what details are important.
  • Sometimes cable specifications allow cable manufacturers to avoid connecting up all of the pins in the connectors on one side of the cable to the other. This is cheaper for the manufacturer and can be okay. (Example, 2 conductors on an RJ11 phone jack.) To avoid ending up buying the wrong type of cable this way, you need to shop for the right specs for your application. For instance, Firewire has two ratings which roughly correspond to speed of transfer: Firewire 400 (IEEE 1394a) and Firewire 800 (IEEE 1394b). When shopping for the cable, you should keep in mind which kind of rating your devices are going for and shop for those.
  • Male/female: You have to be fussily accurate about this or else you’ll get a cable you can’t plug in. In most cases it’s pretty obvious. If you have a prongy sort of connector it’s male and it plugs into a sockety sort of female jack. But what if you’ve got an array of pins inside an overall indentation? Are they male (yes)? Who knows (here’s the “female”)? Use pictures to make sure the terminology you’re using is descriptively accurate for the particular kind of connector you’re using.
  • Speaking of pictures, when I’m shopping on the web, I ALWAYS make sure that the picture for what I’m buying matches up to the description of what I’m buying. If not, I’ll either find another vendor or call the vendor’s phone line.

Styles/Types:

  • Phone cable (jack connectors: RJ11)
    Absolutely the easiest to crimp connectors on yourself with. Need a crimping tool but you can get a decent one for $20. Also easy to connect to other compatible wall-jacks. For in-wall wiring, available as 4-wire “twisted pair” cable. The term “twisted pair” derives from the signal-interference controlling method of twisting the pair of wires around each other on long-runs. For running from wall-jacks to phone usually available in a flat 4-wire cable. Sometimes the flat 4-wire cables are pre-crimped and only connect 2 conductors for conventional Ma-Bell compatible consumer phones. This is absolutely okay, assuming you only need those 2 conductors.
  • Network cabling (jack connectors: RJ45)
    The second-cheapest to crimp yourself. Crimping tools under $20, but requires some wire-stripping as well as punch down tools (if using for in-wall wiring) and maybe some non-trivially cheap testing tools if something goes wrong – with phone, you can just plug in phones where you want to test and listen at the receiver. Network cabling is called Cat5 to Cat6, “Cat” standing for “category”. There are also special ratings for special kinds of EM shielding and for outdoor cabling.
  • Special cabling (USB, Firewire, parallel and serial cables, SATA, video cables etc.)
    At this point unless you are a serious cabling geek, I’d recommend buying cables someone else put together for you. Rolling your own specialized cable requires at the very least a good head with diagrams and specifications, a very small soldering iron, a really precise hand and alacrity with making finished cables look neat and tidy.

Buying in bulk:

  • Bulk cable is often sold in spools and the jacks are not attached. For Network cables, where crimping on the jacks can be a matter of just a few extra minutes and having the right tools (that you can borrow from a geeky friend or buy for $30), this might make sense, but for cables with more complicated ends, it might not.
  • You can get amazing deals (on a per foot basis) for network cables and in some cases can only buy specific types of weather proof network cables in bulk, but be sure you know what you’re getting into. 100′ of cable is usually okay for anyone with a normal amount of storage to hang on to, but 1000′ is a BIG REEL. The good news is that cable recycling is often a pretty lucrative market. You’ve been warned.

Vendors:

  • If you can, avoid buying name-brand cables. You are likely paying for the brand.
  • If you pay for a certain look (like the smooth white coating on many Apple cables), you are generally paying for the look, not the quality of the cables.
  • Bulk cable vendors make money on volume and if you can find the cable you like at the quantity you like you can probably end up paying a lot less

Possible bulk cable vendors:

  • Deep Surplus
    Recently recommended by Kevin Kelly’s Cool Tools. I haven’t done business with them myself, but the Cool Tools submitters often have really good, reasonable buying sense.
  • Cable Train
    Seen this one around.
  • Newegg
    Tend to carry trendy brand names but also tend to carry less expensive generics. I’ve ordered tons of stuff from them. They’re geek-friendly.
  • Monoprice
    Recommended by friends and by CNet.