# Amplified signal path



## avkid (Jul 19, 2005)

In the process of planning a mobile sound rig for outdoor and on location events I ran into the problem of needing to run amplified signal through a snake. I was wondering if it was safe and advisable to run the signal through an XLR snake using 1/4'' adapters on each end?


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## mbenonis (Jul 19, 2005)

Absolutely *not*! The reason is twofold: First, the snake's internal wiring simply cannot handle the amount of current that the amplifier will put out. Second, even if you did it and it worked, the current will induce some nasty interference on the mic channels running along side the speaker channel.

Your best bet would be to go out and buy some inexpensive 14/2 SO cable, terminate it with either NL4 (Speakon) or 1/4 inch connectors, and run it next to your snake. It shouldn't be that expensive if you're willing to put the connectors on yourself (and it NL4/Speakon, it's a cinch!)


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## AVGuyAndy (Jul 19, 2005)

If you want to run speaker signals through a snake, buy powered speakers. (Not sure if you already own the amps/speakers) Other than that, buy some speaker cable and zip-tie it to the snake. If you wanted to get real fancy, you could drill a hole through the stage box for the speaker cable and wire up some speakon/1/4" panel mounts. You could even wire parralel outputs to save on possible cable runs (instead of daisy-chaining speakers)


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## Mayhem (Jul 19, 2005)

Place your amp near your speakers and that way you can run the signal through the snake to the amp. i.e., place the snake between the output from your desk/rack and the amp.

Most snakes with have these "returns" wired into them and you may see a snake specked as 16/4 (for example) which means it has 16 channels to take your signal from the stage to the desk and 4 channels to return the signal to the amp once it has been mixed and processed.

The other advantage of keeping the amps closer to the speakers is that you need less speaker cable to run them. Less speaker cable means less resistance and less resistance means a more efficient system. After all, do you want the amp to produce sound or just to heat up the speaker leads??


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## soundman1024 (Jul 19, 2005)

The snake can not handle that amount of current. To put it into perspective what you are trying to do is run the output of a fire hydrant through a garden hose. The amount of output from the fire hydrant (amplifier) is simply too much for the garden house (snake) to carry. It is actually a hazard to do so. Have you ever felt a cord that had to much plugged into it and was warm or even hot? That is the same thing. If more current were involved it would probably be a fire hazard. It may even be a fire hazard..I have no idea how much current we are talking about here.


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## koncept (Jul 19, 2005)

I have seen a pro company run the mains off a board through a snake to an amp rack. Since the voltage is still line and not amped up, you should not have any problems. I think at most some interference on the mic lines, but that should be almost non existent.


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## Mayhem (Jul 19, 2005)

Exactly - they are using the returns on the snake and I have never seen (or heard) any interference caused. As you point out - it is at line level.


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## Foxinabox10 (Jul 19, 2005)

The problem with powered speakers or amps at the speakers is that means you need power at the speakers. Correct me if I'm wrong avkid, but in trying to make it simple to set up, you'd prefer not to have to run power to the speakers too, right? Plus having the amp next to the speakers means it can't be in your portable rack and therefore the rack slowly becomes unportable.


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## Mayhem (Jul 19, 2005)

True but an extended cable run from Amp to speakers increases the resistance that your amp has to overcome and if you are using small gauge wire, you could end up in loosing a huge amount of power from the amp.

This was a topic that was raised last year in which the exact formulae were posted in working out the resistance of the cable run and then the associated power loss. I converted it into an Excel calculator and found that some combinations can mean that you looses in excess of 50% of your power because of resistance. And this is in speaker cable.

Imagine how great the loss would be in sending it back down a snake.

It would be well worth you doing a forum search on this topic as (from memory) there was some good posts.


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## The_Guest (Jul 20, 2005)

Mayhem read my mind. This one definitely comes to mind...

http://www.controlbooth.com/ftopict-1679.html


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## Eboy87 (Jul 20, 2005)

Now for my two cents. I had an outdoor gig a few days ago, here's how I set it up. As I don't like having amps in my FOH rack, they get their own. I ran the output, after the EQ and comp., through the snake returns, then to the Amp Rack, and then the short distance to the speakers. For power, I had a Furman RP-8 in the amp rack plugged into an extension chord that ran next to the snake back to the FOH rack, and into the RP-8L that I have in it. Worked flawlessly.


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## Foxinabox10 (Jul 20, 2005)

Although this might have worked, it is still not a good idea to run a power cable directly next to an audio cable.


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## Peter (Jul 20, 2005)

And if you do run a powercable next to an audio cable, be sure to be listening for a 60 Hz hum, and know how to eq it out, or move the cable if you hear it.


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## Eboy87 (Jul 21, 2005)

I see your point. I put it there since I didn't want to have cables scattered everywhere for the audience to trip over (even though that was inevitable)


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## avkid (Jul 22, 2005)

I guess I am going to have to cut down a 10 space rack rolling rack to put the amps on. (another full one would not fit in any of the vehicles my family owns.


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## Mayhem (Jul 24, 2005)

when running power leads in close proximity to signal or sound leads the main thing to remember is not to cross the leads over each other but to run them parallel to each other. This will reduce the interference.


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## mbenonis (Jul 24, 2005)

Say what?! I've always been taught to ensure that signal and power are separated by a foot or two, and if they need to cross, they can but only at 90 degrees.


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## Mayhem (Jul 25, 2005)

Well it does depend upon the quality of your leads but I have run them next to one another on some shows simply because of a lack of space.

I should have been a little clearer on the not crossing leads as well. As you correctly sate, if they do need to cross, they should at 90&deg;

What I should have said is not to have them simply run next to each other so that they lay over the top of each other so that they cross over in several points rather than staying straight. Not sure that makes that much more sense either!


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## Mayhem (Jul 25, 2005)

The_Guest said:


> Mayhem read my mind. This one definitely comes to mind...
> 
> http://www.controlbooth.com/ftopict-1679.html



The one that I was actually thinking of was this one:

http://www.controlbooth.com/ftopic-1239-0.html

About half way down the first page is where DMXtools gives an excellent description of the process.


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## mbenonis (Jul 25, 2005)

Mayhem said:


> Well it does depend upon the quality of your leads but I have run them next to one another on some shows simply because of a lack of space.
> 
> I should have been a little clearer on the not crossing leads as well. As you correctly sate, if they do need to cross, they should at 90°
> 
> What I should have said is not to have them simply run next to each other so that they lay over the top of each other so that they cross over in several points rather than staying straight. Not sure that makes that much more sense either!



That does make sense - thanks for clarifying.


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## BNBSound (Jul 25, 2005)

Foxinabox10 said:


> Although this might have worked, it is still not a good idea to run a power cable directly next to an audio cable.



If all your connections are balanced (XLR or TRS 1/4") then you can run your audio cables near pretty much anything you want to and not get hum. I have a 5kW rig set up as such and I've parked my amp racks right next to some ancient SCR dimmer racks and picked up only the slightest hum and that was likely through the speaker runs, not the snake.

It's actually _very_ good practice to power up your amp rack and mix position from the same location with an extension in between, because this assures the same ground potential at both locations. It's much safer for the musos playing electric instruments that way and also a lot more hum proof.


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## Inaki2 (Jul 26, 2005)

Ohhh the ever-present cabling dilemma. This is a bit of a practice-over-theory thing as well.
As Mayhem said, if they have to cross, make sure its at 90, but its not necessarily true, you may cross them at other angles (I've yet to see a tech measuring angles) and not pick up hum also.
Balanced lines do work well, its the whole point of them, and high quality cabling does marvels.
As for different ground potentials, they will affect much more than you may think, since it also affect the chance of creating a ground loop. Ho Hummmmmmm


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## Mayhem (Jul 26, 2005)

What - you don't carry a protractor with you?


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## Inaki2 (Jul 26, 2005)

Nope....*blushes*


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## avkid (Jul 26, 2005)

Inaki2 said:


> high quality cabling does marvels.



Such as empty my small wallet alot more quickly!


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## Inaki2 (Jul 26, 2005)

Yeah, those good connectors will do that even faster!


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## Eboy87 (Jul 26, 2005)

That's what birthdays are for


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## Inaki2 (Jul 26, 2005)

Ha! Yeah mom, a spool of cable and Switchcraft connector...thats right.


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## Eboy87 (Jul 26, 2005)

hey, i got my Drive Rack for my birthday


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## Inaki2 (Jul 26, 2005)

Really? Wow...I wonder if I could ask for a Catalyst =)


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## Foxinabox10 (Jul 30, 2005)

Here's a snake that's isolated inside and allows you to send powered runs:

http://www.whirlwindusa.com/power01.html


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## Eboy87 (Jul 31, 2005)

Better yet, try this: http://www.lightviper.com/products.aspx#. I'd love to get my hands on one of these


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## Inaki2 (Jul 31, 2005)

Personally I like the Whirlwind E-Snake much better, the LightViper has selectable gains, only 3 of them, which kinda pisses me off.


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## Eboy87 (Jul 31, 2005)

Yeah, that is nice. But I don't think either will be in my rig soon.


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