Buzzzzzzzzzzzzzzzz

[nd925a]

My csd has an aud with a really screwed up aud....they have a hug rack backstage left that has 6 amps runing to 2 speakers, a digital mackie mixer and 2 wireless handhelds.
my problem is when i put an external board through the mixer i get a buzzing kind of humm that sounds like to much power running through the speakers, but the handhelds run through the digital fine.....question is how do i fix.

[Stookeybrd]

How are you running the sound from the outboard to the Mackie?


Balanced? Unbalanced?

From an Aux, from a Group, from Outputs?

What does your gain structure look like?



Also if you fully type out each word, more people can help you.

[nd925a]

sorry about the short typing....
i'm putting the outboard in through a port in the back wall of the auditorium labeled mic 3
gains on the one mic i had to test with was all the way down
i'm still new so i can't answer your 2nd and 3rd questions
i can get specifics and pictures soon hopefully

[Hughesie]

try to isolate cable issues and provide more details about when it happens.

For example if you told us it took place during a show while lighting was fading then your issue could be there. But if it is happening all the time chances are the grounding on the cable has come loose or your running the cable near a large electric source such as an epod.

[Eboy87]

Originally Posted by nd925a

...my problem is when i put an external board through the mixer i get a buzzing kind of humm that sounds like to much power running through the speakers, but the handhelds run through the digital fine...

So, let me see if I've deciphered this correctly.

You have a PA in your auditorium. Your mixer, which I shall refer to as a console, sounds like a Mackie TT24. Now, your system is fine when run normally, i.e., just the handhelds running through the Mackie.

You're getting a buzz (which sounds to me like a ground hum, around 60 Hz, 50 Hz if you're overseas) when you plug in another console to yours, correct? That's what I get by reading your original post. Or are you referring to an outboard processor (typically referred to as "outboard"), like an equalizer, compressor, gate, effects processor, etc?

Is this "mic 3" input in the auditorium getting the output of another console or a microphone? I'm under the impression that another console is plugged into it. If that's the case, (well, regardless if it's a console or not) start unplugging things until the buzz goes away. What is likely happening is that there is a piece of equipment that is on a different circuit than the rest of your PA. Voltage is leaking into the ground on the different circuit, which creates a voltage potential between the two pieces of equipment, as the shield wire (think of it like a ground wire) in the mic cable connects the two, whether it be two consoles, or a console and outboard gear. That shield wire lets the offending gear send voltage down it to the other equipment, which is what creates the buzz.

Now, you just have to determine whether you're using two circuits or not, and isolate the offending gear. If you're just a student, I would suggest having an adult help you with that part (my apologies if you are an adult). If you find the piece of gear creating the buzz, and put it on the same circuit as FOH (the Mackie and its outboard), your buzz should go away. If it doesn't, then there's likely a different problem. But let's tackle this one first.

[nd925a]

hughesie
a) what's an epod????
b) it's all the time and the port to backstage is in a brick wall

[nd925a]

eboy
when i said outboard i ment an external mixer
i am a sophomore in hs
sorry for any confusion
some local adults are putting on a production in an elementary school where there's noone even close to a td
the "console" is not a tt24 it is a small 1 or 2 rack space thing with colored bars that move up and down with buttons to do so
and the external mixer is the only thing plugged in to backstage besides the wireless handhelds

[David Ashton]

Sorry but you are in way over your head, either get someone in to help you or do some serious reading of the basics of sound systems especially gain structure, you will then be in a position to explain your problem in a meaningful way.Unfortunately your description makes no sense.

[Eboy87]

Buy the Yamaha Sound Reinforcement Handbook, and read it. It'll help.

Yamaha Sound Reinforcement Handbook on Amazon.

[lieperjp]

If you don't want to buy the book, check out the wiki entry on Gain Structure. It will give you an idea about what it is.

Gain Structure