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Strange behaviour - Stage Monitor Feedback Loop


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Hello everyone,

I ran into some very strange behaviour the other day.
What I experienced was a feedback loop through the stage monitors, in sound checks.

My setup is pretty standard. Guitar > Helix > 'Poweramp-in' on my Hot Rod Deville.

Pre-Amp model of the Engl. No distortion pedals. Drive on the amp-block around 4.0.
A typical metal patch including bog standard compressor, noise gate. Obviously no cab emulation.

We were asked to have our backline volume down on stage to adhere to H&S, so I was running the amp at a much lower level then I normally do. Respectable, considering the amp was being mic'd up anyway.

Essentially, I'd get high pitched feeding (Squeel) after my palm muting... the gate would cut it off, but considering the size of the system, that squeel was running throughout the room. Horrible stuff.

The sound engineer lowered the level of my guitar in the monitors, which cleared it up. I was just so surprised to have run into this. Not once in my life have I experienced electric-guitar monitor feedback and I've done my fair share of sound engineering also.

I really don't want to run into this issue in the future as it sure messes with my nerves. That, and the whole show I had fear of going near any of the other monitors on the stage as their monitor mix could've been louder than mine. I could certainly hear a lot more of my other guitarist in nearby monitors.

Any suggestions?

I thought perhaps my amp level was actually too low onstage?

Passive pickups, hot humbuckers... but no need to turn guitar input PAD on because of my recorded tones behaving just fine at that level.

If I stand in front of my amp at rehearsal volume, I struggle to get deliberate feedback?


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Well my first thought is does it have anything at all to do with your guitar/Helix/amp? You were mic'd - could it have had more to do with the mic and the monitor?

Some things to consider - what type of mic? Placement of mic/amp/monitor? Gain setting on the mic? It was a squeal? - not guitar feedback? Turning down your monitor fixed it?

Feedback when you weren't playing not when you were? Sounds like it was the sound guy's problem to me. Your guitar may well have been overriding the feedback (louder than the sound that was looping back at the mic) when you were playing, so you'd only get it in the gaps.

Another potential cause, (but not very likely) - microphonic pickups. But you'd have experienced that with any high gain sound before then.

Now obviously you would have had to be there and run some obvious experiments to really know - but I can't see it being anything to do with the Helix.


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I agree with @rvroberts. This "sounds" like the sound man's issue, and not yours. Having done sound for my band for a number of years now (I am NO expert though) that this type of squeal sound would be more typical to mic/monitor issues rather than a guitar issue. I think you should be confident moving forward that YOU or your setup are NOT the problem here.

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  • 3 weeks later...

Thanks for the replies everyone.


I puzzled over this for a little while and I think the squeel was probably caused by the compressor settings.

I presume with a bigger rig, the engineer was applying his standard compressor levels to all instruments... this could've been doubling up on my helix compression.


Not really important : I setup an Eq at the start of my signal chain that reduces lows... that way the compressor was being applied on a "flat" guitar eq. I'd return the lows with parametric Eq later to taste.


I think the -30db threshold might've been a little brash, even with the mix lowered giving a "parallel compression" effect. When I was setting the patch up through studio monitors, the amount of compression sounded subtle... but after tinkering with the amp at practice, i could hear the difference the compressor was having more clearly.

I've dialled the compressor threshold back 5db, then lowered the mix to a point where it's audibly makin a difference... but it's a subtle thing.

Without the compressor, the clean snapshot sounded lifeless... and really helped as an indicator of what's happening before the amp block.


Although the settings felt amazing to play and sounded like the holy grail, I'm much happier knowing I'd done something to combat the Squeal. The settings still play nice enough... and with compression from FoH, it probably will balance out my reduction.

(Please give us some graphical charts within the helix Line 6, showing volume, compression amount, and prarmetric eq "q" width)

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(Please give us some graphical charts within the helix Line 6, showing volume, compression amount, and prarmetric eq "q" width)


Agreed, we could really use some sort of visual feedback so we can see when the compression is kicking in to set the threshold properly.

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