1 (edited by Maddcow 2022-06-06 09:23:45)

Topic: UFX+ and earthing issues

Hi all
I'm a sax & EWI player using a UFX+ with MacBook Pro and Sennheiser wireless mic and IEM systems.

One show I'm involved with has started doing a lot of high-end theatre shows and I was told the other night that my rig is emitting electrical noise...not much, but enough for the theatre AV guys to be unhappy about it.  I was stunned because I've never encountered this before but the AV guys said that's likely due to many gig venues not having very low noise floors, whereas high-end theatres are very very picky about this sort of thing.

After much testing, we found that the UFX+ XLR outputs are emitting ground noise.  There's no noise from the 1/4" outputs and when the UFX+ is connected to a separate power line (as opposed to it usually being on the same powerboard in my rack as numerous other devices), the noise disappears. 

I'm not an electrical/electronics/AV guy and would love some thoughts/answers/advice re. the following:

a) Why the UFX+ XLR outputs have noise in the first place?
b) Why ALL the UFX+ outputs don't have noise (i.e. why is there only noise at the XLR outputs and not the 1/4"?)
c) Why there's noise from the XLR outputs even when there's no power to any devices in my rack, including the UFX+?
d) Apart from running separate power to the UFX+, is there any way to completely eliminate the noise instead of applying band-aid solutions such as isolator boxes etc?

Cheers in advance, guys.  I'm keen to learn about these things and would really appreciate any advice.
Gary

Re: UFX+ and earthing issues

Hi Maddcow,

It sounds like you could be experiencing what is known as a "ground loop" in this venue.  It would be silly for me to explain it when it has been thoroughly explained here https://www.audioholics.com/home-theate … m-and-buzz

Good luck!

Re: UFX+ and earthing issues

Maddcow wrote:

c) Why there's noise from the XLR outputs even when there's no power to any devices in my rack, including the UFX+?

This should tell you the noise isn't being produced in the UFX+.

So the question is, "What else is connected that could be producing that noise?"

My first guess is a laptop...

MB Pro - 2 X FireFace 400, FF800 & DigiFace USB
ADAT gear: Korg, Behri, Fostex, Alesis...

4 (edited by boz6906 2022-07-31 17:51:48)

Re: UFX+ and earthing issues

Check to ensure the AC polarity of the supply to your rack w/UFX is the same as the polarity of the house system you are connecting to.