Multichannel DIs

#1

I am gearing up to finally build my studio and a thinking about Direct boxes. I will record mostly rock music (guitars, bass, drums, keyboards) in the studio and will need some DI boxes but I was thinking to decrease clutter, it could be very handy to just have a few multichannel DIs build directly into the wall. Has anyone done this? Is this a good or bad idea? I was also thinking along similar lines that would be best to have 8 channels mounted in 3 of the 4 walls of the live room (since I will run 24 channels) and these can then connect to the pre-amps. This type of stuff was not in the design Stuart made for the construction (at least I don't think it is in the sketch up file).

Thanks for your input. Top view is below.
scott

#2

Dr Space wrote:Source of the post it could be very handy to just have a few multichannel DIs build directly into the wall.

You could do that, yes. Build them into the stage box panels themselves, to have some dedicated sends for instruments.

I was also thinking along similar lines that would be best to have 8 channels mounted in 3 of the 4 walls of the live room (since I will run 24 channels)

I would go with more than that. Even if you only have 24 channels on your console, I would still have way more than that for actual lines from the LR to the CR. Normally you have a patch bay somewhere close to the console where you can select which feeds from where are actually hooked into the console (or DAW) inputs. Its common to have most of those normalized for "standard" situations (such as having the first ten feeds coming form the drum mics, direct to the first ten inputs on the console), and then only use patch cables when you need to change that, and do something different. That gives you greater flexibility, and simplifies your life: You don't need to running into the LR each time you want to select a different input: just make a patch.

This type of stuff was not in the design Stuart made for the construction (at least I don't think it is in the sketch up file).

Actually, it is!

On the front wall of the live room, under the window. (That was an earlier version of the studio, when we still had a window in that wall, and no windows in the stone wall).

You can see it more clearly here:

There's also another one on the opposite wall, under the window to the Control Room:

Each of those has 16 XLR sends, 8 XLR returns and 8 LRS plug lines. Those are normally for things like headphones and for amps, but they could go in either direction, depending on how you patch them, in the CR. You could use a few of those for direct boxes, certainly.

Those panels are basically just meant to be place holders (similar to most of the acoustic treatment show there), and would likely be different in the actual room. You would probably want several CAT6 and USB channels on each panel as well, and maybe other things too.

But that's the general concept, and having some DI built into the panels themselves makes sense.

One other thing: I would suggest that you bury the conduit for all of that in the slab itself, right up to the position where the desk will be, and also bury other conduit in the slab, going from everywhere to everywhere, like we did in Tom's studio: http://spartanew.digistar.cl/Forum/view ... p=354#p354 and here: http://spartanew.digistar.cl/Forum/view ... p=378#p378 (also other posts following that).

Conduit is cheap, embedding it in the concrete before the pour is simple (but do read the caveats I gave Tom about it floating!), and it gives you great flexibility when it comes time to cable everything together. Run conduit for electrical power as well, to provided power wherever it might be needed. And run extra parallel conduit at each point, for future expansion, or in case the original one is damaged during construction. It's just PVC, and it doesn't cost much, so even if you never actually use it, it's not a big deal. But if you do need to run extra stuff in the future, it's fantastic to have the conduit there, ready to do that. Run several sizes: big ones for the snakes to the stage box panels, smaller ones for "other stuff", and for electrical power.

- Stuart -

#3

Hello Stuart..... They are going to start very soon with tearing down the ruin and the plan for the foundation that the contractor has now does not include having anything in the foundation. Can't all of these cables just run in the walls? My time is running out to make any changes and I would have to have an exact plan of how and where these conduits were to go if I am going to pull this off. I think it is actually too late to do this. Glad you agree it is ok to put some DIs in the wall with the XLR channels in the walls.

Thanks
scott

#4

Dr Space wrote:Source of the post Hello Stuart..... They are going to start very soon with tearing down the ruin and the plan for the foundation that the contractor has now does not include having anything in the foundation. Can't all of these cables just run in the walls? My time is running out to make any changes and I would have to have an exact plan of how and where these conduits were to go if I am going to pull this off. I think it is actually too late to do this. Glad you agree it is ok to put some DIs in the wall with the XLR channels in the walls.

Thanks
scott

In the floor is more direct runs and cheaper. You have a good plan for working where to put them. You have followed my tagline.

Enjoy!

#5

Avare wrote:In the floor is more direct runs and cheaper. You have a good plan for working where to put them. You have followed my tagline.

Everyone should follow Andre's tag line, always.

- Stuart -

#6

Update for the rest of the forum: Scott and I have been talking by e-mail as well, but I'll just add on some of what we discussed here, for continuity:

Dr Space wrote:Can't all of these cables just run in the walls? My time is running out to make any changes and I would have to have an exact plan of how and where these conduits were to go if I am going to pull this off. I think it is actually too late to do this.

Yes, you could run most of it in the walls, but as Andre mentioned, running in the floor means shorter runs, and it's cheaper and simpler in the long run.

The one place where it makes the most sense to run things in the floor, is to the desk. The console and outboard gear that you'll have in the desk needs to be connected all over the place, and since the desk sits out in the middle of the floor, it makes sense to run several large conduits to that, so there's no cables laying on top of the floor.

Also, use way more conduit than you need: it is chap and simple to install, and you never know when you might need to run additional cables in the future. So for each place where you figure you need one conduit, run three of them and leave two empty. It does happen that one conduit might get damaged during the concrete pour, and become unusable, so having a couple of spares is a a good thing. (been there, done that!).

You can place the conduit in the slab form-work, and tie it down to the steel mesh. If you don't anchor it, then it will float up in the wet concrete to the surface, ... :shock:

... so tie it down firmly. You also don't want it to move if a careless worker kicks it. If there's no steel mesh or rebar in the slab (which might be the case, especially if it's just a screed layer on top for the floor), then use duct tape to tape the conduit down to the insulation or vapor barrier plastic. You could place a few small rocks around it, to weight it down, if all you have is the 6 mil plastic down there and nothing else. I've never done it myself, but I have heard of people threading some metal chain through the conduit too, to add weight, then pulling that out once the concrete is set.

A couple of extra points here:

Put "fish tape" in every conduit while you are installing it. "fish tape" has nothing at all to do with fish, and usually isn't even tape either! It's just some type of strong "string" that you use to pull the actual cables through when the time comes. Often it is semi-flexible steel, nylon, or fiberglass on a roll. (see here: https://en.wikipedia.org/wiki/Fish_tape ) You thread it into the conduit as you are installing it, and leave both ends poking out with a little extra looped around. Then when the time comes, you attach the wiring to one end of the fish tape, and pull on the other end to guide it through the conduit. There are also "wire pulling lubricants" that you can us if things get too tight.
Use only GENTLE curves in the conduit! Don't make very tight bends. If you do, you'll have a really hard time trying to get the wring through. So use only broad radius bends. I often use a large bucket as a guide for the radius when I'm bending conduit.
To bend the conduit: if you are using typical PVC electrical conduit, you heat it until it softens a little and is pliable, then bend it to any shape you want. However, when you try to bend it with just your hands, it usually kinks, twists, mangles and collapses in on itself! And ends up looking like this:

Bad! So you need something called a "bending spring":

conduit-bending-spring-3.jpg (32 KiB) Viewed 41322 times

conduit-bending-spring-3.jpg (32 KiB) Viewed 41322 times

. That's just a flexible metal spring that you push down inside the conduit before you heat it. The diameter of the spring is just a little smaller than the diameter of the conduit, but it is sold according to the conduit internal diameter. So if you use 20mm conduit, then get a 20mm bending spring: it will be a bit smaller than 20mm, but that's correct: it needs to be a loose fit inside, so you can push it in. Attach a piece of wire, or strong string to the loop on the end BEFORE you put the spring in the pipe! You use that to pull it out again after it is bent.

conduit-bending-spring-inside-with-string.jpg (30.12 KiB) Viewed 41320 times

conduit-bending-spring-inside-with-string.jpg (30.12 KiB) Viewed 41320 times

I use a blowtorch on a very low setting to heat the conduit just enough so it can be bent, then bend it around the bucket with the spring inside, and you get a very nice smooth curve. But do be careful! Playing with fire is dangerous. And if you get the conduit a bit too hot with the blowtorch, it will discolor, char, and even burn. Practice on scrap pieces first... You can also use a heat gun, or even a hair dryer, to heat it up. It is safer to use a heat gun, but it takes longer to heat.

heating-and-bending-pvc-pipe.jpg (38.72 KiB) Viewed 41313 times

heating-and-bending-pvc-pipe.jpg (38.72 KiB) Viewed 41313 times
On the other hand, if you are using metal conduit, then you need a different type of bending spring that is flared at one end or both ends, like this,

... and goes OUTSIDE the pipe, then you just bend it around your knee:

... or you need one of these "pipe bender" tools:

pipe-bender.jpg (17.34 KiB) Viewed 41320 times

pipe-bender.jpg (17.34 KiB) Viewed 41320 times

pipe-bender-3.jpg (5.7 KiB) Viewed 41320 times

pipe-bender-3.jpg (5.7 KiB) Viewed 41320 times
Make the conduit too long! Leave a section poking out the floor at both ends. You can always cut it down to the right size later. It is easier to see when it pokes up many inches above the floor, and is less likely to get damaged.
Before the concrete pour starts, plug the ends of the conduit with rags or newspaper stuffed down inside a bit. You do not want concrete, water, dust, or debris getting inside the pipes! Keep that in place until the very end, when you are actually read to pull the wires through.
As soon as the concrete is set, put upturned buckets over the ends of any conduit that pokes up through the floor, and put a heavy brick on top. That's to protect the conduit from careless workmen. It isn't very strong, so if you kick it or drop a tool on it, it will crack. The bucket is there to protect it, and the brick is there to hold the bucket down. I have also been known to duct-tape the bucket to the slab...

If I think of any other pointers, I'll add them here, but those ones will make your life easier.

- Stuart -

#7

Great stuff! I can not judge what the progress is, but before its too late do the mic and line level runs with AES/EBU cable.

#8

I’m thinking post #6 is worthy of the reference area! Very helpful information!

I’m still wrapping my head around running snakes through the conduit...I guess the ends have to be bare wire and soldered into wall plates from there once the walls are framed? (Obviously there’s no way you could have conduit large enough for a bunch of XLR tips on every cable lol)

Do you have to get the conduit to pop up in the tiny space between the walls? Seems like it would be difficult to get this placement perfect since the walls aren't up yet when the conduit is placed and concrete is poured. But it must be doable! Measure twice cut once kind of thing.

Thanks Stuart and Andre! And lovely looking studio you got there Scott!

Cheers,
Trevor

#9

shybird wrote:Source of the postI’m still wrapping my head around running snakes through the conduit...I guess the ends have to be bare wire and soldered into wall plates from there once the walls are framed? (Obviously there’s no way you could have conduit large enough for a bunch of XLR tips on every cable lol)

I've been wondering the same. Certainly wires running to wall plates will be more robust long term, assuming they are soldered competently in the first place. Snakes with attached XLRs pouring in to the room would logically be more prone to mechanical damage at their ends.

I've fed XLR snakes through very short lengths of narrow duct, one tip at a time

For those of us not particularly competent or fast solderers, or to rooms only for occasional use, I wonder if it would be possible to feed an XLR snake through a longer duct if it was sufficiently wide and had gradual bends. My first thought would be to wrap or tape all the XLR tips in a line, attach the fishing line to the first one, then pull...

Cheers,
Jennifer

#10

Jennifer

endorka wrote:Source of the postI wonder if it would be possible to feed an XLR snake through a longer duct if it was sufficiently wide and had gradual bends. My first thought would be to wrap or tape all the XLR tips in a line, attach the fishing line to the first one, then pull...

The only thing I would say is to make sure you are tugging on the cables, not the XLR plugs.

#11

Starlight wrote:Source of the post Jennifer
endorka wrote:Source of the postI wonder if it would be possible to feed an XLR snake through a longer duct if it was sufficiently wide and had gradual bends. My first thought would be to wrap or tape all the XLR tips in a line, attach the fishing line to the first one, then pull...
The only thing I would say is to make sure you are tugging on the cables, not the XLR plugs.

Good point, and therein lies the rub. It might be difficult to do this without pulling the cable ahead of the plugs and getting everything wedged up. I wonder if it would be possible to wrap the plugs and end of the cable into something like one of these spiral cable jackets, and then pull on that?

Cheers,
Jennifer

#12

I thought you had it with your first thought, just tie your fishing line to one or more cables, not to the first plug as you wrote. I would wrap the whole bunch in cling film or a plastic bag - maybe a spiral cable jacket, as you say, but I am not sure that would stay closed) and tightly wrap the whole lot in masking tape or the tape of your choice so the head of the snake can slide through the conduit or duct without having a poking out bit to get snagged. You see, apart from what you tie to, I think your first thought is spot on.

#13

Greetings Jennifer,

A friend of mine did this by sliding the cable bundle into a stocking (leaving room at the toe end; more on this), cinching with a cable tie below the toe and on the other end (a snake sausage, if you will), tying fishing line to the toe end, and pulling it through.

I know it worked, but I don't know how far or how many bends were negotiated in the process.

Bang(er) on,

Paul

#14

endorka wrote:Source of the post For those of us not particularly competent or fast solderers, or to rooms only for occasional use, I wonder if it would be possible to feed an XLR snake through a longer duct if it was sufficiently wide and had gradual bends. My first thought would be to wrap or tape all the XLR tips in a line, attach the fishing line to the first one, then pull

For anything more than maybe an 8+4 snake, you'd need a REALLY large conduit to do that. That's a whole bunch of XLR connectors!

What I have done for shortish runs, is to line up several XLR connectors one behind the other, in groups (like wagons in several trains running side by side), then wrap all that in plastic, attach the fish tape to the cable jacket (not the connectors, just like Starlight said!!), and wrap the whole bunch with electrical tape, then smear it all liberally with wire-pulling lubricant. But we are talking at least 3" or 4" conduit here (75mm - 100mm), with no bends (or only very, very gentle bends), and runs of just a few meters. Even then, it is a slow, messy job, needing at least two people, better three (one pulling, one feeding the cable in, and the third guy applying more wire lubricant). And unpacking all that electrical tape and plastic wrapping without damaging the conductors or connectors is ... ummm.... shall we say "fun"! :ahh:

The alternatives are:
1) Pull the snake without any connectors on, then solder them on afterwards. This is the recommended method, but soldering all those things on again is a major pain! Can you say "Boring!"? Maybe hire a smart kid from your local technical school to do that for you.
2) Pull many single cables, two or three at a time, with the connectors on. Not recommended: by the time you get to the third or fourth bunch, things start getting very tangled inside the conduit! Can you say "cable jam"?
3) Don't even try! Just run the snake all by itself through the walls, connectors and all, but without conduit, then seal up the large penetrations you had to make to get it through... And take into account that the snake ain't never commin' out agin! So make sure it has way more pairs than you'll ever need, in your wildest dreams, to allow for future expansion, bad pairs, etc.

That's about it! Not a lot of options here. #4 would be to just do it all digital, and run thin CAT6 cables... but that's a little pricey for a typical home studio, and introduces latency... plus you are stuck with the pre's and converters used by the manufacturer, which not be be your first choice....

Maybe someone else has other ways of doing this, but those are the only ones that i have used!

PS. I would not recommend using fishing line: you'll wreck your hands, and the conduit, and maybe the cable too, with that stuff. Rather, get yourself some proper electrician's "fish tape", and use that.

Fish tape:

- Stuart -

#15

Apparently, we've reached the "Today's Recipe" part of the thread: cable sausages and cable jam. But remember, do it wrong and you're toast.

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