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Author Topic: Direct run guitars feeding back through FOH  (Read 6831 times)

Jerry Smith

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Direct run guitars feeding back through FOH
« on: December 10, 2012, 09:54:55 AM »

Hi all, need some advice on were to start looking -

My band(3 guitars, bass, keys, drums) all play through pedal board/amp sims, and we all use IEMs.  The only thing acoustic onstage is the drums.  We are getting some nasty feedback from the guitars at FOH.  I know the first suggestion will be gates, but this feedback is nearly immediate when they stop playing.  To get gates to cut them off it's going to sound like someone turning the guitars on and off with a light switch, and not in a good way.

Our tops are EAW LA325s w/ Yamaha 218s on the bottom.  We are always behind the stacks, and our guitarists are usually at least 4-5 away from the stacks.

I'm really at a loss of where to start looking.  It took a lot of convincing to get my guitarists to ditch their amps, and if this continues I'm going to lose them back to their 4x12s :(
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g'bye, Dick Rees

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Re: Direct run guitars feeding back through FOH
« Reply #1 on: December 10, 2012, 09:57:46 AM »

Hi all, need some advice on were to start looking -

My band(3 guitars, bass, keys, drums) all play through pedal board/amp sims, and we all use IEMs.  The only thing acoustic onstage is the drums.  We are getting some nasty feedback from the guitars at FOH. I know the first suggestion will be gates, but this feedback is nearly immediate when they stop playing.  To get gates to cut them off it's going to sound like someone turning the guitars on and off with a light switch, and not in a good way.

Our tops are EAW LA325s w/ Yamaha 218s on the bottom.  We are always behind the stacks, and our guitarists are usually at least 4-5 away from the stacks.

I'm really at a loss of where to start looking.  It took a lot of convincing to get my guitarists to ditch their amps, and if this continues I'm going to lose them back to their 4x12s :(

I think the problem is likely to be compression.  Quit playing, the compressor releases and the input in question gets hotter than the threshold of feedback.
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Mac Kerr

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Re: Direct run guitars feeding back through FOH
« Reply #2 on: December 10, 2012, 10:03:26 AM »

Hi all, need some advice on were to start looking -

My band(3 guitars, bass, keys, drums) all play through pedal board/amp sims, and we all use IEMs.  The only thing acoustic onstage is the drums.  We are getting some nasty feedback from the guitars at FOH.  I know the first suggestion will be gates, but this feedback is nearly immediate when they stop playing.  To get gates to cut them off it's going to sound like someone turning the guitars on and off with a light switch, and not in a good way.

Our tops are EAW LA325s w/ Yamaha 218s on the bottom.  We are always behind the stacks, and our guitarists are usually at least 4-5 away from the stacks.

I'm really at a loss of where to start looking.  It took a lot of convincing to get my guitarists to ditch their amps, and if this continues I'm going to lose them back to their 4x12s :(

Since they are direct, and not mic'd, the feedback must be either from something else, or electronic, not acoustic. Turn every other mic off at the console and try each guitar individually to see if it is just one of them. If they all still feed back with all other mics off, try eliminating pedals one at a time to see if it is happening in a pedal. It sounds like something is in heavy compression, and when the playing stops the compressor releases and adds a lot of gain to the system.

Mac
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Bob Leonard

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Re: Direct run guitars feeding back through FOH
« Reply #3 on: December 10, 2012, 10:23:51 AM »

Volume and compression. Less volume, no compression, bring back the amps in the form of something 40 watts or less. However, if they insist on half stacks use a good mic up close. If you're playing smaller venues and they're using half stacks then you really don't need to mic the cabinets or put them hrough FOH anyway. Stage volume will be enough.
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John Roberts {JR}

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Re: Direct run guitars feeding back through FOH
« Reply #4 on: December 10, 2012, 10:30:45 AM »

+1 too much compression...

JR

[edit] to explain why this causes the feedback after they stop playing... the compression turns down the gain when they are playing loud, but the desk operator pushes up the gain on the faders to compensate and get back some of the lost signal, negating the effect of the compression that reduced that gain. 

When the loud playing stops, the compressor releases the gain reduction, effectively turning up the gain, so you get high enough gain to sustain the feedback.

If the mix engineer is turning up the guitars in the mix because the compressor is turning them down too much, turn them down less, with less compression.   [/edit]
« Last Edit: December 10, 2012, 10:40:50 AM by John Roberts {JR} »
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Jerry Smith

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Re: Direct run guitars feeding back through FOH
« Reply #5 on: December 10, 2012, 11:08:53 AM »

Ok, I didn't think to look at the channel compression at FOH, I'll take a look at that.
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Tim McCulloch

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Re: Direct run guitars feeding back through FOH
« Reply #6 on: December 10, 2012, 11:22:33 AM »

Ok, I didn't think to look at the channel compression at FOH, I'll take a look at that.

Re-read Mac's post.  It could easily be in the stomp box/amp modeler chain.
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Ned Ward

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Re: Direct run guitars feeding back through FOH
« Reply #7 on: December 10, 2012, 11:52:28 AM »

I'm confused, as I used to play through a rackmount guitar setup and was never able to get guitar feedback from the PA...

How loud is the PA?
Are most of the guitar patches super high gain/distorted?
What amp sims/floorboards are they using specifically?

My guess is that they are using patches with WAY too much gain. Sounds great on the in-ears. Try a different patch or have them dial back the gain by half.
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Jerry Smith

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Re: Direct run guitars feeding back through FOH
« Reply #8 on: December 10, 2012, 06:34:45 PM »

I'm confused, as I used to play through a rackmount guitar setup and was never able to get guitar feedback from the PA...

How loud is the PA?
Are most of the guitar patches super high gain/distorted?
What amp sims/floorboards are they using specifically?

My guess is that they are using patches with WAY too much gain. Sounds great on the in-ears. Try a different patch or have them dial back the gain by half.

One is a Boss GT-10, I forget what the other one is.  The gain on the sim preamp is what I was thinking initially.  They are both used to pretty overdriven tones from their stacks.  This gives a couple things to try at least with looking at the compression too(both FOH and sim patches)
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David Buckley

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Re: Direct run guitars feeding back through FOH
« Reply #9 on: December 10, 2012, 06:45:51 PM »

One is a Boss GT-10, I forget what the other one is.  The gain on the sim preamp is what I was thinking initially.  They are both used to pretty overdriven tones from their stacks.
That's the place to look.  Sims tend to get set up in isolation, often in bedrooms at quiet volumes :) and thus the gain is would up beyond 11, beyond Mesa, right up to buzz.  You need to wind it back.  The lack of volume and lack of context makes the extent of the overdrive not obvious.

The odd thing is when the overdrive is set to buzzsaw the actual definition of what is played is lost, and so the guitar level goes up in the mix, and it doesn't really improve matters, just makes the mix muddier, so the next thing the sound guy tries to fix it with is eq, and it just keeps going downhill.

A bit of work on fixing the sim settings will deliver enormous benefits all round.
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Re: Direct run guitars feeding back through FOH
« Reply #9 on: December 10, 2012, 06:45:51 PM »


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