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[jan house]

Hi all,

I'm playing guitar in a live cover band, have had 2 good sound engineers running from stage, both with a lot of experience. They can't figure this out -- I'm hoping someone here can.

 I use a "side wash" position, somewhat behind and to the side of me, as I use an in ear for vocals in my opposite ear. This happens when the p.a. stack is to my right, several feet away, and my amp is on my right, as I said angled up at me. PRS through a Roland 80 watt amp, also happens with my combo tube amps. Amps mic'd up with a Sennheiser E609, also happens with a Shure '57.

The problem is, when, because of the size of the venue, my amp is near or even behind the stack  (Yorkville bass bins,  Yorkville full range speakers mounted on the bass bin by way of a pole) -- I get a nasty high pitch squeal, similar to a microphonic pre amp tube, on my hotter distortion settings with compression, to the point of those settings being unusable.

If the channel in the board is muted, there is no squeal whatsoever. I don't play at loud stage volumes. If I'm anywhere else on stage, I don't get the squeal. I can be near the opposite p.a. stack no problem, my amp in that position is maybe 10 feet from the stack, blowing towards it.

Changing channels on the board makes no difference, nor does changing mic cables.  It seems to be an issue between the amp (hot settings only), the mic, and the p.a. Very hi pitched squeal, not usable feed back at all. If I bring my volume down a bit, and play notes rather than the volume being up and not playing, I can get away with it, with a few squeals here & there.

Thanks for any opinions or ideas, my sound guys are mystified.

[lindsay Dean]

you are using a instrument cable between your amp and your guitar and effects to your amp right ?

[lindsay Dean]

are you wire less on iem or guitar ?

[jan house]

by golly yes I'm wireless, whilst trouble shooting hadn't thought of using a cable to see if it made a difference.

Wireless on both iem  and guitar. Sennheiser in ear system and Line 6 guitar wireless.

[Lee Douglas]

Interaction between your pickups and the mains?  Doesn't happen on the opposite side because you stay further away to avoid hitting you neck.  Just a guess.  I get something similar if a get too close to the mains with my bass.

[Luke Geis]

As a guitarist of 27 or so years I can say simply, it is feedback between the PA and the guitar. Here are a couple things that cause it:


1. The amplifier gain setting ( the distortion gain, not the actual master gain ) is too high. This is probably the number one cause of premature guitar to amp feedback. However, if under unsupported use ( no support through the PA ) there is not a problem, then this would not be the case. Try it anyway just to weed its possibility out.

2. The pickup height is too high ( too close to the strings ). When the strings are too close to the pickups, the sensitivity between them is increased and any sympathetic vibrations between the two can run off. The string pull on the strings from the pickups magnets can also cause the strings to pull out of intonation. The magnetic flux is so saturated by the strings energy that any sort of vibration in the strings is transferred into the amp, including the vibrations caused by the PA.

3. The stage volume is too low and the PA level is too high, or you are too close in proximity to the PA regardless of stage volume. I would call this a good thing actually! It means that you are quiet enough to actually need significant support in the PA!

When you have a quiet stage level you usually require a bit of PA support! This is great if you can hear what you need to hear and you don't have the issues you're currently having. It could be a combination of all three points above actually? In either case, there is a couple things you can try:

1. Lower the amps distortion gain a little bit and see if that helps. This is usually my first go to, but if your already modest on gain settings then this will be moot. A little less distortion gain will help clean up the sound and won't actually make the guitar sound any less raunchy believe it or not. Obviously if you have to crank it way down, this is not the issue.

2. Have your sound guy invert the channels polarity, or if you have a digital desk that will allow for it, delay the guitar channel several milliseconds, or a little of both and see if that helps. The feedback induced by the PA to guitar will be a time vs. amplitude thing. So changing the polarity and or the time of the reproduced signal out of the PA will change the frequency and potentially the gain at which the feedback will occur. Usually one or the other will fix it, but using both may both improve the odds and the quality of sound.

3. If all else fails, raise the stage volume a little bit so that you require less PA support. From a quality of FOH sound standpoint, this would be my last resort, but you have to fix the problem. The lesser of two evils sort of thing.

[Roland Clarke]

As Luke says, it's feedback sure enough, just narrowing down the cause.  Running the amp low and gaining up using foh can cause all sorts of problems on small stages.  If the volume at the mic starts to get higher from the pa that will do it, also it could be the guitar feeding back to foh.  Personally I wouldn't want a cab close to the pa, perhaps trying it behind you tilted up towards your head and monitoring at a comfortable level so that you balance on stage without monitor, (I'm assuming you are playing small bar/club stages).

You need to run through all the scenarios that Luke suggested and eliminate them one by one to locate the problem.

[Gordon Brinton]

I think what is happening is cancellation of the mids and lows, on your guitar amp, making the ugly "high graininess" of the distorted sound become more noticeable.

When you are behind the PA main stack, you will hear mostly lower-mids and lows because those frequencies wrap around the cabinets in all directions and radiate outward from the cabinet wood itself. The highs do not. If the main stack is the same distance away as your combo amp, cancellation may occur at those frequencies, causing you to hear only highs from your guitar. This explains why when you move away, you no longer hear it. If it were actual feedback, you would here it all over the stage and venue.

Test this theory, (during sound check,) by having the sound guy roll-off the lows and mids on your guitar channel in the pa. If the sound from your amp becomes more full and the squeal seems to go away, it is low-end cancellation.

EDIT: If this is the case, he may be able to fix the problem by running his pa in stereo and panning your guitar mostly to the opposite main speaker stack, thus avoiding low end spill from your side.

[John Ferreira]

There is no way you should have to change guitar settings, or amp gain. I can use any gain I want with my PRS, right up to extreme distortion plus a pedal to distort even more, and I never get microphonic feedback, even at over110 dB on stage.

Try different components, one at a time. I would try a different guitar amp, just to start, and take it from there.
Are you using any pedals?


Sent from my iPad using Tapatalk

[jan house]

thanks all for taking time to respond, and think about, the issue.

One thing I had not mentioned is, I've worked with my current bassist/sound guy since 1988. My amps have varied (tube or solid state), same p.a. for maybe 10 years. . .but this problem has only occurred in the last 3 or 4 years, possibly the same length of time that I've had the wireless. First time I noticed it was small club, only place for amp was behind the stack. (I might be using lower stage volume these days, as mentioned below).

the feedback is very high frequency, really a shriek or squeal -- as I said microphonic sounding.

I'm using a condenser vocal mic, but this has also happened with my EV767. Not sure if the vocal mic be involved as amp does aim at it somewhat, & I'm a "girl singer" with a medium volume vocal, so the mic is probably pretty hot.

Agreed, seems to some kind of loop so I guess that is technically feedback, just not the good kind ;-)

I do use fairly low stage volume, we're an older band and very vocal & harmony based, so I'm probably boosted a good amount in the mains. The bassist runs me more "in" the mix than in front of the mix, he's a bass/drums kind of guy, but there may enough in there to interact with my pickups.

One other clue -- I can use my rhythm setting, with overdrive, but my lead setting using same overdrive but with "turbo" engaged and 20% louder, gets the squeal, while my rhythm setting does not. (Effects unit a "vintage" Roland GP8 processor, don't laugh, has a very nice overdrive).

For what it's worth, my pickups were actually very low, I looked at PRS's setup guide while fooling with my guitar last night and measured, mine were twice as low as the recommendation. I raised 'em a bit, sounds quite a bit better at home anyway.I wonder if them being too low caused a problem?

So you've all given me some good stuff to try. I'll do the following this weekend:

Removing some gain and/or compression from the hotter settings. Time to re configure my sound anyway.

Using a cable instead of wireless, just to see what happens.

Getting the guitar (not amp) further from the p.a. cab

Roll off lows & mids in the p.a. channel

I'll print this off & huddle up with the sound guy, in case I missed anything, and let y'all know what happens. Thanks a bunch!

Jan

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