live sound

[aizo]

well, you guys are always so nice and helpful...

i was wondering if anybody knew a thing or 2 about live sound?

i have a 24 channel mixing board with 4 busses.

i have 2 monitors and 12 speakers for FOH.

as of right now i have a 100 ft snake. that has essentially the same set up as the mixing board. 4 trs' for aux's and 16 xlr's. currently, i use send's 1 and 2 on each channel to send to the monitors(the sends are of course trs). the monitors have a hum in them. i'm sure the reason is
that i have to use the 2 trs i/o's from the snake. then put an adapter on my xlr cable to go into the back of the monitors(the monitors are powered mackie 450's and the only input on them is xlr). so, should i just buy a male xlr-trs? is this what's causing the hum? is there a better way to go about configuring monitors in which i can add and subtract from the monitor mixing by individual tracks. in a nutshell, how can i get rid of the annoying hum?

[Macinbowl]

The reason you have this hum is because you probably use an unbalanced jack. With a balance trs jack, the hum should go. If you'r already using a trs jack, then I would assume the this is an electrical hum. You could try a "Pin 1 lift" xlr adapter. It may also come from the console itself. Then you could try ground lifting the console. If all of this doesn't solve your problem then let me know, I may have a couple more "troubleshooting" trick on hand!

But my feeling is it come from the wrong adapter...

Good luck!

Mat

[daniel.sneed]

I agree with Macinbowl.

When I get trough this type of trouble, I of course try to keep everything connected in "balanced lines", that's standing for 3 points connections.
This from mixer to stage amp.
Practicaly, your snake must be : shield + cold wire + hot wire. This means all trs, if any, are stereo ones.

You must check in your mixer datasheet, that your mixer offers real 3 points outputs (called balanced outputs) for monitors. Specialy if they're trs, cause you can't see it from outside the box !

You must check that your stage amps are real 3 points connection inputs (called balanced inputs). Specialy if they're trs, cause you can't see it from outside the box either !

The required tool when you can't check your equipement before working day, is to cary in your pocket one, or two, good double transformer isolation boxes. Typicaly a double 600-600 Ohms box, with two earth lift buttons.
When you encounter hum trouble, you connect it at one end of your snake, beteween mixer and snake, and move the earth lift buttons combination, listening to any change in hum. If you don't get good results, try it at the other end of the snake, between snake and stage amp.

This basical tip has got me quickly out of many trouble sound installs.
Works equally for fold-back and front of house, of course.

[TreyG]

If you are not using all the channel from your snake you can reverse the connections on each end to give a balanced signal.
I use srm450's for monitors and this works great for me.

[Shooshie]

The required tool when you can't check your equipement before working day, is to cary in your pocket one, or two, good double transformer isolation boxes. Typicaly a double 600-600 Ohms box, with two earth lift button

Could you give me an example of such a pocket-sized box? I really don't know what I'm looking for, and googling double transformer isolation boxes doesn't yield much to go on.

Thanks,


Shooshie

[Shooshie]

If you are not using all the channel from your snake you can reverse the connections on each end to give a balanced signal.
I use srm450's for monitors and this works great for me.

Can you be more specific? Let's say I have a snake of 8 trs lines, and I've got 7 of them employed. What do I do to the 8th one? (in literal, step-by-step terms if possible, for this electronics-challenged do-it-yourselfer.

Shooshie