One of my favorite scenes in Ghostbusters is when Egon gives the guys a warning about crossing the streams. As we know, it’s not good. Not good at all.
Dr. Egon Spengler: There's something very important I forgot to tell you.
Dr. Peter Venkman: What?
Dr. Egon Spengler: Don't cross the streams.
Dr. Peter Venkman: Why?
Dr. Egon Spengler: It would be bad.
Dr. Peter Venkman: I'm fuzzy on the whole good/bad thing. What do you mean, "bad"?
Dr. Egon Spengler: Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.
Dr Ray Stantz: Total protonic reversal.
Dr. Peter Venkman: Right. That's bad. Okay. All right. Important safety tip. Thanks, Egon.
That scene played out in real life for me a few weeks back. Well, sort of. I didn’t exactly experience total protonic reversal, but I did discover that it’s a bad, bad thing to cross the streams in a redundant Dante network. But let’s back up a step.
Two Types of Dante Networks
There are a few different ways to lay out a Dante network. Ignoring topologies for a moment, you can either set up a redundant network or a switched network. All Dante devices have two Dante network ports on them, and they will be labeled Primary and Secondary. By default, most devices have those two ports connected together in switched mode. That means you can plug one device into the primary and another device into the secondary and data will flow freely between all three devices.
The benefit of this method is that you don’t need any switches. Just keep daisy chaining all the devices together and the network works quite well. The downside is that if any link in the chain breaks, audio stops flowing. If you had a console and computer at FOH, two stage racks, a processor and a few amps on stage and someone breaks the cable between the two stage racks, you will lose audio in the house as the data is no longer flowing from the console all the way through to the system processor and amps.
Now, you could just take all the primary ports and connect them to an external switch. That way, if you lose one link, only that device is affected; the rest of the system still functions. This is clearly a step up in reliability from the daisy chain, but you can still lose a device if a cable fails.
That’s why the better option is a redundant network. In a redundant network, you connect all the primary ports to a switch (or series of switches, depending on the layout) and all the secondary ports to another switch or set of switches. I highlight “another” because it’s very important that the networks remain separate.
Don’t Cross the Streams
I learned this lesson the hard way a few weeks ago. It turns out that if you wire the system up properly, with all the primary ports going to one switch and the secondary ports to another, but have one device set up as a switched device, you essentially build a bridge between the two networks. And that’s bad. While you don’t have total protonic reversal, you do get what is called a broadcast storm, and the switches freak out. The only way to fix it is to separate the networks and power cycle everything on the network.
Dante devices will stop working properly, probably won’t pass audio and devices will not mount properly. Basically, it’s bad. I chased this problem for a while before my friend Jake Cody helped me figure it out. I learned an important lesson that day, and it changed the way I will set up a Dante network next time.
You might be asking, why bother with redundancy if it’s so fraught with peril to set up? Well, it’s really a safety net. When we used analog copper snakes, one wire could go bad, and we’d still have signal in the others. In say, a 56-channel snake, if you lost one channel, you still had 55. On a 16-channel drive snake, you could patch around a channel that went bad. Even if you lost 2-3 of them, most of the system would still function. And if you got creative, you could make it all work.
But when the entire system depends on four 24 gauge solid copper conductors, it doesn’t take much to wipe the whole system out. If one of those wires breaks, you don’t lose 75% of the system; you lose it all. Or if a single switch freaks out, you can lose the whole network. And the only way to fix it is to stop audio, and reboot or reconfigure.
Building a redundant network will let you fix a problem in one leg while the other still passes audio. For any system that is mission critical—and that pretty much means all of them—you should go redundant.
Next time, I’ll share with you my revised process for setting up a network that will work the first time.