running di box thru snake
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Posted on Jul 24, 2010 10:51 pm
bcastle
Member Since: Jul 24, 2010
I started running the sound board again at our church with a larger set up and have been asked to solve a problem of our guitars and pianos humming.
I have been doing alot of reading trying to get myself up to speed with the equipment and our layout.
We have (2) behringer ultra di pro 4000 di boxes in the sound booth but they are not connected.
Our cable layout is as follows:
(4) plug in boxes on the stage for instruments, mics and monitors that each have (2) 1/4" connections and (2) xlr connections. From here they go to the snake box under the stage and connect via XLR. then into the mixer (behringer 2442). Im assuming that the xlr connections from the stage boxes to the snake boxes are balanced, the 1/4" im not so sure about, i'd have to pull them up.
My questions:
Can I plug an unbalanced 1/4" cable from my guitar into a 1/4" connection in one of the stage boxes then have the balanced snake xlr go into the input on the di box and finally have the output on the di box connect to the mixer?
For the above scenario, does it matter if the cable between the stage box and the snake box is balance or unbalance?
Do the instruments need to be connected with one unbalanced 1/4" cable from guitar directly or indirectly, using the 1/4" stage box connection, wired unbalanced of course, to the input on the di box then the xlr output on the di box to the snake, then snake to sound board?
To do the latter, i would have to mount the di boxes under the stage (easy, just dont want to do because it's dusty, no air circulation, might forget to turn them on ect) or put them in a closet behind the stage (have to run more cable, dont want to do that either)?
Thanks for any input.
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Jul 25, 2010 12:22 am Hey there bcastel. Welcome to the HRC.
What it sounds like to me, is that your having an unbalanced cable issue to begin with. This would account for the hum and buzz that your hearing.
Unbalanced cables can not be ran long distances. Just for this reason. The wire becomes an antenna looking for any signal to pick up and take to the other end.
Now a balanced cable is two wires that are acting like antenna's. The only difference here is that the preamp is reading the difference between the two wires. And canceling out any hum or buzz.
The best configuration for you to run is, to run a some what short 1/4" cable (Under 20') to the DI box. DI box to your snake, via the XLR. then snake to board. If you get any buzzing with this configuration, you have a way out. And that is a ground lift switch that is on the DI box. If your still getting a buzz, simply lift the ground at the DI box. This should eliminate this. If it does not, then you have an issue with the wiring in your snake. Meaning that one of the wires in the snake are broken.
Give this a try, and write back and let me know how it went.
Jul 25, 2010 10:09 am I was kinda thinking that I was going to have to mount the di boxes closer to the stage. I've taken a few circuits classes and understand the theories of sound travel. However, keeping the 1/4" runs under 20' is going to be physically impossible for the mere fact that the distance from the stage box at the front of the stage to the closest place i can run the di box under the stage and still access it easily will be close to 20' then add a 10' guitar cable. Im sure that the 10' wont make that much of a difference. I might have to use some beefy shielded cable.
I'll still try it though. For the mean time i'll just put the di boxes on the stage out of the way. Luckily I only have 4 instruments and they are on one side of the stage. It will just look tacky until i can figure a way to keep the dust away from the di box.
Thanks for the help.
Jul 25, 2010 09:59 pm Okay, this afternoon after service with the help of another sound guy, I rewired (3) 1/4" female connections in 2 of the stage boxes. Originally the cables were male xlr at the snake box connection and then they cut and soldered the ground and another wire (blue i think) together on one side of the jack and then the red wire was soldered to the other part of the 1/4" jack (this part of the jack is the back side of the female 1/4" so I can use the male side of an unbalanced instrument cable. (you probably already know this, but i like to try and clarify things)
We tested each 1/4" plug with my electric guitar in the following order: :
1) plugged guitar directly into the di box with unbalanced cable, used about 40' of xlr to snake.
2) plugged guitar into both 1/4" connection in the stage box closest to the di box with unbalanced cable(15' of unbalanced cable run from stage box to di box) , xlr cable was the same
3)plugged guitar into 1/4" connection in the stage box farthest away from the di box (for sake of ease and time I simply connected (2) 20' long unbalanced cables together with a female-female connection), xlr cable was the same.
I noticed that the longer the unbalanced cable was, the more trim I had to add on the sound board.
I still have some more testing and adjusting now, but it will have to wait until I get back from out town with work.
One other question: Is it normal practice to use an xlr cable, bridging two of the three wires together through a 1/4" connection (like the same ones i'm using for the instruments) and use this as a monitor connection? I'm sure the wiring is consistent to the amp.
Jul 25, 2010 10:42 pm I'm a little confused on how the snake box is wired here.
You say that the XLR's are wired to an unbalanced 1/4" female jack? Or did they move a pair of wires to the 1/4" female jack?
Either way, the ground should never be with any other wire period. It should be it's own. I have used the two color pairs to the tip of a 1/4" connector. That's fine. And you get a small amount of cancellation of hum and buzz with a twisted pair that way. But, yes, you lose a small amount of signal as well.
Really, the bast thing to do, is to keep the DI as close to the guitar player as possible. A balanced signal will run over 500' before having any issues.
As for running the monitor off of a snake line converted to your monitors input......... Yeah, don't do that. Reason being that mic cable is .22 gauge in thickness. WAY to light to handle the loads of a amp and speaker load. You want at least 12 gauge wire on there to be able to handle the power, wattage, and load.
Jul 29, 2010 07:31 pm Thanks for the reply.
I think for our physical layout, I'm going to have to look into possibly using a couple of passive di boxes for just the guitars that way I dont have to have 40+ ft of unbalanced cable plus a really long extension cord run too.
As for the monitor, the set up has worked with very little problem as our problems are too many to list. Ie our snake runs 3 inches away from a row of 10 pairs of fluorescent bulbs down the length of our sanctuary. Because it "keeps it out of view". Never mind the fact that our building is old enough not to use normal 3 prong grounded plug ins. I guess we will need to invest in some bulk spool cable and lots of connectors.
Thanks
