help with two zone mixer (urgent!)

[veven1290]

first of all i'm Ben, nice to meet you.

second, my problem.

The sound system at my work has been having issues, i have no experience or knowledge in this area but the task of fixing it was somehow delegated to me.

we are running two TOA 900 series II amps and a QSC model 1200 pro stereo amp out of a Rolls Zonewolf RM68 two zone mixer.

the inputs are an ipod, a cd player, a DISH tv audio receiver, and there is one mic.

when ever we turn the mixer on there is a very loud buzz, obviously if we unplug the three amps from the mixer the buzzing stops. If we even plug one amp back in the buzzing continues, so i've figured out that it's not a problem with one of the amps since all three of them buzz when plugged in.


this could be a very simple fix, again i have no idea what i am doing so if you have any ideas i would be extremely grateful.

thank you for the help

 

[T2T]

Can't you call up the company that did the intitial install?

 

[JohnA]

Sounds like a possible ground loop issue, if you unplug the Dish receiver from the mixer with the amps hooked up do you still get a buzz?

 

[TLS Guy]

first of all i'm Ben, nice to meet you.

second, my problem.

The sound system at my work has been having issues, i have no experience or knowledge in this area but the task of fixing it was somehow delegated to me.

we are running two TOA 900 series II amps and a QSC model 1200 pro stereo amp out of a Rolls Zonewolf RM68 two zone mixer.

the inputs are an ipod, a cd player, a DISH tv audio receiver, and there is one mic.

when ever we turn the mixer on there is a very loud buzz, obviously if we unplug the three amps from the mixer the buzzing stops. If we even plug one amp back in the buzzing continues, so i've figured out that it's not a problem with one of the amps since all three of them buzz when plugged in.


this could be a very simple fix, again i have no idea what i am doing so if you have any ideas i would be extremely grateful.

thank you for the help

You have a ground loop which is a potential between grounds.

Disconnect the satellite system and see if the buzzing stops. If it does you can not use an isolating transformer with satellite systems, so you will have to tie the satellite grounding block to the building ground, with heavy 4 gauge wire. That is code anyway.

If the hum persists with the satellite box disconnected then, just ground the mixer, and lift the other grounds.

Make sure the building ground is good. I use three seven foot large copper rods tied together as my building ground.