samgraysound
Well-known member
Hi all,
I've been asked to figure out a buzz issue at a local radio station. I went down there to see what's up on Monday and I'm going back next week to start working on it. I have some ideas but I wanted to see what I might not be thinking of or things to try.
Here's the issue:
Whenever a mic is plugged in there is crazy buzz on that channel.
This is true for any of the 4 input channels
No buzz when mic is unplugged.
The volume and quality of the buzz changes as the mic is moved around and rotated
The signal flow is Mic --> preamp/processor --> console.
The power routing is wall --> hum-x --> UPC --> Power conditioner
There is two different computers also on the same circuit
cabling was redone recently but I haven't looked closely at it yet.
Everything is wired through wiring blocks secured to the bottom of the desk. the console inputs are all on snaking that goes from the wiring blocks to 12-pin connectors inside the console.
All the mics are on adjustable arms secured to the desk, the mixer is bolted to the desk, the computers and rack gear are on a rack bolted to the desk.
Here's ideas I have to try:
1. Check for mechanical noise by removing mics from mounting arms
2. Make a ground lift cable and try lifting ground on each side for each leg of the signal path
3. Try an 1:1 isolation transformer at each leg of the signal path
4. Put the audio gear on a different power circuit then the computers.
5. Take the audio gear off the upc.
6. check the system ground for the mixer, make sure it is tied to electrical ground, and that all the rack gear is tied to the system ground
7. check each leg of the signal path with a portable headphone amp.
Any other ideas? Also is there a way to tell if their power has unwanted voltages or interference riding on it? Can I look at it with an oscilloscope and see?
I've been asked to figure out a buzz issue at a local radio station. I went down there to see what's up on Monday and I'm going back next week to start working on it. I have some ideas but I wanted to see what I might not be thinking of or things to try.
Here's the issue:
Whenever a mic is plugged in there is crazy buzz on that channel.
This is true for any of the 4 input channels
No buzz when mic is unplugged.
The volume and quality of the buzz changes as the mic is moved around and rotated
The signal flow is Mic --> preamp/processor --> console.
The power routing is wall --> hum-x --> UPC --> Power conditioner
There is two different computers also on the same circuit
cabling was redone recently but I haven't looked closely at it yet.
Everything is wired through wiring blocks secured to the bottom of the desk. the console inputs are all on snaking that goes from the wiring blocks to 12-pin connectors inside the console.
All the mics are on adjustable arms secured to the desk, the mixer is bolted to the desk, the computers and rack gear are on a rack bolted to the desk.
Here's ideas I have to try:
1. Check for mechanical noise by removing mics from mounting arms
2. Make a ground lift cable and try lifting ground on each side for each leg of the signal path
3. Try an 1:1 isolation transformer at each leg of the signal path
4. Put the audio gear on a different power circuit then the computers.
5. Take the audio gear off the upc.
6. check the system ground for the mixer, make sure it is tied to electrical ground, and that all the rack gear is tied to the system ground
7. check each leg of the signal path with a portable headphone amp.
Any other ideas? Also is there a way to tell if their power has unwanted voltages or interference riding on it? Can I look at it with an oscilloscope and see?