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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Jerry Smith on December 10, 2012, 09:54:55 AM

Title: Direct run guitars feeding back through FOH
Post by: Jerry Smith 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 :(
Title: Re: Direct run guitars feeding back through FOH
Post by: g'bye, Dick Rees 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.
Title: Re: Direct run guitars feeding back through FOH
Post by: Mac Kerr 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
Title: Re: Direct run guitars feeding back through FOH
Post by: Bob Leonard 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.
Title: Re: Direct run guitars feeding back through FOH
Post by: John Roberts {JR} 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]
Title: Re: Direct run guitars feeding back through FOH
Post by: Jerry Smith 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.
Title: Re: Direct run guitars feeding back through FOH
Post by: Tim McCulloch 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.
Title: Re: Direct run guitars feeding back through FOH
Post by: Ned Ward 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.
Title: Re: Direct run guitars feeding back through FOH
Post by: Jerry Smith 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)
Title: Re: Direct run guitars feeding back through FOH
Post by: David Buckley 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.
Title: Re: Direct run guitars feeding back through FOH
Post by: Ned Ward on December 10, 2012, 10:57:23 PM
Investing in a good 50-75' guitar cable will let them get off stage and down in front of the PA to hear what it sounds like. Guessing scooped mids, which in a band context combined with massive gain means sonic mud.

With them playing out front, have another band member tweak the gain, and then they'll be a lot happier vs. telling you that "No, Dude - this is my sound and it rocks at home!" (i had the same thing on several presets and ended up programming a live bank of presets and one for the home studio).
Title: Re: Direct run guitars feeding back through FOH
Post by: Bob Leonard on December 11, 2012, 07:29:27 AM
+1
Title: Re: Direct run guitars feeding back through FOH
Post by: Aaron Kelley on December 11, 2012, 09:09:03 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 :(

Hey man, I mix sound at my church and to be honest, we rock it loud. Our lead guitarist goes through a tube amp that I have double mic'd that I placed in a corner where it doesn't spill over the stage too much and he is so happy to be able to run through the amp. Which makes me happy too because as a guitar player also, I love tubes. Besides that, our rythem guitarst is going stright through the PA with a pedal board. I've never had feedback from him because I tell both guitarist to keep the gain at 11-12 o'clock. If they have any delay or reverb in a digital pedal, they need to check the gain and threshold on those. If it's not the pedals or compression, check your gain on your console. If you are running your faders below 0 and -6 and are running your gains high, that could be the problem also.
Hope this helps.
Title: Re: Direct run guitars feeding back through FOH
Post by: g'bye, Dick Rees on December 11, 2012, 12:47:06 PM
If you are running your faders below 0 and -6 and are running your gains high, that could be the problem also.

Nope.  Gain is gain is gain, no matter whether it is at the pre or  the fader.  Running the pre hot and the fader low is the same as running the pre low and the fader high......or running them both properly.  It's all the same in the end except perhaps (with cheap gear) the S/N ratio.
Title: Re: Direct run guitars feeding back through FOH
Post by: Tim McCulloch on December 11, 2012, 12:49:46 PM
Nope.  Gain is gain is gain, no matter whether it is at the pre or  the fader.  Running the pre hot and the fader low is the same as running the pre low and the fader high......or running them both properly.  It's all the same in the end except perhaps (with cheap gear) the S/N ratio.

+1.  Gain is gain is gain.
Title: Re: Direct run guitars feeding back through FOH
Post by: Aaron Kelley on December 12, 2012, 10:23:15 AM
Nope.  Gain is gain is gain, no matter whether it is at the pre or  the fader.  Running the pre hot and the fader low is the same as running the pre low and the fader high......or running them both properly.  It's all the same in the end except perhaps (with cheap gear) the S/N ratio.

ok. sorry for the misunderstanding. Scratch the gain portion.