Analog audio cables vs. Digital audio cables

[Jetmanjames]

First post to the site. This place is awesome! I can't believe the amount of information I have found and that is just the audio side of the site! Thank you all for what you do.
I'm working on making my own "snake" for a new install. We are planning on purchasing the LS9-32 so I will need 32 in and 16 out. So I was figuring on running 50 balanced mic cables from sound booth to stage (about 100+ ft.). I was going to use the Beldin 9451 cable for all of it but then I saw the Belden 1800B cable. The price is more than double for the 1800B. My question is what is the difference between the analog rated and the digital rated cable? And do I really need to use the digital rated cable with the LS9?

[prochlea]

You're going to be sending analog signals from the stage to the board, so you don't need digital. That said - I wouldn't run 50 single cables from the board to the stage, I would use some multipair snake cables. Belden has them with 8 mic lines in one jacket - 1512c - and I'm sure they have higher pair counts. It will save you tons of time. I'm partial to the Canare Starquad snake cables L-4E3-2P (or 4p, 8p, 12p) You'd be able to run 8 or 12 mic lines in one pull. I don't know how your stage is setup, but you could probably do some floor boxes or wall plates with 8 jacks in them. It would save you so much time that it would be worth paying more(i think it costs more, but i'm not sure) Pulling 50 lines is gonna be a huge pain unless you have 10 spools of wire and can do it in a few pulls. Personally, I'd get 5 12-pair cables cut to the length you need, and do one wire pull.

[Brad Weber]

It depends! One issue is terminology, although they may use the same cable, there are significant differences between 'mic' and 'line' level signals and thus when referring to "mic cables" you seem to be referencing cables carrying microphone signals when I really think you are referencing the cable type and not the signal being carried.

This can become relevant as while at least for now, mic signals are virtually always analog signals, however line level signals on digital consoles can be analog or any one of a number of different forms of digital. So a typical snake for a digital console might be addressing multiple mic, analog line and digital line level signals, even if it is all analog today it might be desirable to support some digital lines for the future.

Digital audio signals such as AES/EBU require appropriately constructed digital audio cable, they will likely not work properly with analog cable. However, most analog devices, both mic and line, will usually work fine with a good quality digital audio cable. The biggest differentiator for digital audio cable is probably that it is 110 Ohm impedance and usually low capacitance compared to analog audio cable.

Thus how many of each type of cable to be used can depend upon the application and budget. If you have all analog mic and line level signals then you could use all analog cable. If you have a few digital signals or want to provide support for that in the future, you could use digital cable for the related runs. Or you could use all digital cable for the most flexibility, but also probably for a higher cost.

You could also look at using multipair cable such as Belden 1805F (8pair), 1806F (12 pair), 1850F (16 pair) and 1852F (24 pair) or similar options from West Penn, Mogami, Canare, etc. Not quite as good a solution if you have individual runs going to many different locations but perhaps a good option where you have multiple runs to the same location or device.

[Jetmanjames]

Thanks guys. That clears it up.
Thanks for the heads up about the multipair cables, Pat. We are planning on 7 stage boxes so I'm thinking 4 connections per box should be good. I'm thinking I'll use the 4 pair setup. I've got plenty of room to 'pre-pull' the cables (lay them on the floor, the length of the sanctuary) and cut them to length and then pull them (all 12, 4 pair cables) through the 2" conduit at the same time. I should have enough of room in the 2" conduit right? We have four 2" conduits that run straight from stage to soundbooth for future use if we ever needed to run a few digital cables or any other cables. If it gets too tight for the 12 cables, I'll just split it up and run it through the other conduits.
Thanks again for the help.
______________
James Westra
Faith Community Church

[kbob]

well, another way to go-one that might leave you with more flexibility overall-is to use a single large stage box, then feed the smaller stage boxes from that.

In that event, you'll have one larger "master" snake, terminated on stage with a patch bay or spider snake ends, and use those to feed your stage boxes using the smaller four channel snakes.

I'm not sure there's an advantage to have 12 home runs of 4 channel snakes versus a multi channel snake.

[Jetmanjames]

Is it possible to get away with not having a patch bay? I'm going to have to run my speaker sends to an amp at the back of the stage then up to my speakers. So I will have a rack to put a patch bay in but I'm thinking a patch bay will only double the amount of ends we'll have to solder and increase the points of failure. I can see the ability to be able to group the inputs for different setups on the stage but I can do that at the board. It's even easier to group things on a digital board. So I'm wondering what are the advantages of having a patch bay?

[kbob]

there's a lot more to it-but a lot boils down to this:

advantage of a patch bay (in this case, I'm really talking about a patch panel, which is a lot less work, but lets keep with that terminology for now):

flexibility-if your stage gets rearranged, or you add new members of the band, or a keyboardist adds or changes connections/gear, then you have the ability to move stuff around independently of which smaller snake they end up in, without changing the board channel assignment. Of course, you can do some of that by repatching things at the board end, but sometimes you just run out of ways to rearrange things when you're limited to one sub-snake at a time.

disadvantage-more soldering/points of failure.

advantages of the sub-snake approach-more home runs, equals less points of failure.

disadvantages-if one channel goes bad, it's much harder to move things around to cover the remaining areas.

[waynehoskins]

Originally Posted by Jetmanjames

Is it possible to get away with not having a patch bay? I'm going to have to run my speaker sends to an amp at the back of the stage then up to my speakers. So I will have a rack to put a patch bay in but I'm thinking a patch bay will only double the amount of ends we'll have to solder and increase the points of failure. I can see the ability to be able to group the inputs for different setups on the stage but I can do that at the board. It's even easier to group things on a digital board. So I'm wondering what are the advantages of having a patch bay?

Advantage of a proper patch bay: you can re-route any or all of the processing chains as desired, and rearrange the channel hookup on a console, all from at the console. Flexibility, and the ability to re-route around a failed device, are the advantages. With a normalling bay, the default condition is to remove all the patch cords, which is wonderful.

Disadvantages: expensive. Long-frame patch cords aren't quite a common thing any more. Inexpensive patch bays tend to develop dirty contacts over time if they're not often exercised. Lots more terminations.

I find I take example from David And Craig who avoid them. I like the flexibility, but they're another place for failure to occur, and as somebody smart once said, "the parts that aren't there can't break".