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XLR output noisy with mono, quiet with stereo*


trhx
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I'm not using any stereo effects live, so I decided to go XLR mono. That will let me feed one XLR to FOH and the other XLR to our monitor rig when we're in that split situation. Unfortunately, the mono output to the mixer is extremely noisy regardless of which cable I use. When I switch back to stereo, the noise goes away (caveat below). This is all while connected to a UI24 mixer in our practice space, and I created or removed the stereo link on the mixer channels as needed.

 

The caveat is that the stereo connection is only quiet if the Helix left out is connected to the mixer stereo link "right" input. If the left out is connected to the "left" in on the mixer, that channel is noisy. No noise from the Helix right output, regardless of which channel it is plugged into.

 

This is a relatively easy fix, and it's no problem to run the Helix 1/4" line out to the monitor rig when needed, but I'd still like to know why it's happening if anyone has any ideas.

 

 

 

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Weird. Both XLR outs (L and R) should behave the same - there shouldn't be a difference in noise depending of which of them you use. But they should also behave the same regardless of what input you plug into.

 

A potential issue:

The Helix outputs automatically sum to mono if using only the left (mono) output. This is true for both the 1/4" and XLR outputs.

 

This could be an issue if your patch has the right stereo channel phase flipped. It would result in almost no signal when using the left channel only (L and R would cancel each other out when summed) which would appear noisier if you compensate for volume after Helix.

 

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The simple fix if you're going to FOH with the L/Mono output is to have your mixer simply send that signal to your floor monitor on a separate monitor output.  That's what's usually done.  Simple and works flawlessly every time.

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On 2/26/2025 at 11:08 AM, DunedinDragon said:

The simple fix if you're going to FOH with the L/Mono output is to have your mixer simply send that signal to your floor monitor on a separate monitor output.  That's what's usually done.  Simple and works flawlessly every time.

Thanks, but getting a monitor feed isn't the problem I'm trying to solve. That info was just context for the FOH/monitor split at the source (Helix XLR outputs). The mystery noise from the left output is the real issue, but if the stereo feed is the only thing that fixes it, I can live with the mystery.

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On 2/25/2025 at 10:22 PM, Schmalle said:

This could be an issue if your patch has the right stereo channel phase flipped. It would result in almost no signal when using the left channel only (L and R would cancel each other out when summed) which would appear noisier if you compensate for volume after Helix.

Thanks. I'll check it out, but there's no volume drop for the preset using the mono output only - just added noise on top of the signal.

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Try the same with 1/4” outputs. 
Try to test factory presets. Back up, do a factory reset and repeat the experiments. 
 

As I already mentioned many times, there is a bug with summing l and r to mono. Maybe in your case it’s introducing weird noise. 
 

Just watch my video to see this bug for yourself. 
 

https://youtu.be/PtUkL7aHeFY?si=sUupSIBifgknbH5w

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