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I was always intrigued with the way Ted Nugent/Adrian Belew/Jeff Beck/Jimi Hendrix/SRV were able to control feedback and make it musical - are there guitar/amp settings and techniques that can make this kind of control a part of a players repertoire?

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Great question! –  Jduv Jan 24 '11 at 17:59
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I remember a G3 video with Steve Vai where he taped large X's on the floor at different points on the stage. At one point he was feeding back and he stepped from point to point and the tone of the feedback changed, so it leads me to believe that there may be some property of feedback that can be taken advantage of--possibly related to harmonics. I'll research this a little bit and see if I can uncover something cool. –  Jduv Jan 24 '11 at 18:27
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If you watch some of Santana's videos you'll see him turn and freeze to lock in a note. Distance affects the frequency as does volume. Natural harmonics (octave, 2nd octave, fifth above that) are jumps you can control pretty easy, especially if you use artificial harmonics to encourage the pitch change. –  Anonymous Jan 25 '11 at 0:13

8 Answers 8

Kind of reinforcing what others have said but with some disagreement in my experience : I use a Marshall 1970's amp with a nice warm full sound, a strat (unmolested) and a Boss BE-5 effects board which has distortion and compressor, whcih I set so that the volume is the same whether clean, compressed or distorted.

Feedback occurs when some magic happens between the resonant characteristics of your amp, your guitar the note being played and the room itself. Between them they gang up and at some locations in the room (mainly relative to the amp) cause some notes/strings to ring almost indefinitely.

I can get feedback easily with the compression and distortion on (I don't use much) by standing a little away from the amp, normally to one side a little, and letting a note/chord ring. It doens't have to be too loud but that sometimes helps. It;s more about the sensitivity (gain) on the effects and the position of the guitar.

However .. * Using the tremolo arm/vibrato to vary the pitch doesn't 'keep it going' in my experience - it actually mutes/disturbs the feedback a little, and adds a lot of depth to it, but I have to wait for the feedback to join in again if I do this too much.

  • Adding a bit of delay (echo) can reinforce the feedback (I guess it's re-playing the note that's already feeding back) and make it more controllable, and allows for more vibrato loveliness.

  • If you get too near the amp, you get a different kind of feedback: direct from the pickup (single coils especially) which isn't related to any notes being played, is a high pitched squeal and is a nasty sound.

  • Sometimes the feedback gets out of control and you can hear it's going to get way too loud too quickly. To control this, I reduce the guitar's volume knob just slightly, down to ten ;-) I tend to grab the volume control quite quickly as I know I won't need that hand for plucking strings once the feeedback has started, but don't want to go blowing people's ears with nasty piercing stuff. You can use this to

  • As soon as you mute or re-fret the string, the feedback is disturbed and will possibly stop so if you want to change the note during the feedback, maybe anticipate bending a string once struck & allow it to sing away at you :-)

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One way of "faking it" is to use a pedal which can self-oscillate, like the Zvex fuzz factory. At some settings it will produce feedback sounding noise even with no volume from the guitar. It can be set so the volume control controls the shrieking. To the untrained ear, this will sound similar to feedback (which in some sense it is, but not the classic amplifier type which is discussed here).

The benefit is that it becomes more controllable, independent of position and can be reproduced at lower volumes.

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The way I usually do it on stage is as follows:

Run a guitar straight into a Line 6 Pod X3 Live and then take that into the DI input for the venue backline (this lets me use my preset amp simulators) and have a pretty loud front of stage monitor.

In soundcheck I take a good look at where I can get feedback and although I don't mark them on the floor, I note where I need to be for particular songs or sections. I also set the volume so feedback will only happen at full volume on my guitar. When I don't want feedback I slightly back off on my volume or tone.

If I get feedback slightly wrong, I can move forward or backward a very small amount to get it to sound 'in tune'

caveat - this works well for loud rock and metal. Not so good with an acoustic guitar mic'ed up. For that I always rather have my monitor behind me so feedback doesn't ring so harshly.

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Hendrix would walk around the stage with his guitar during soundcheck and mark the "sweetspots" with masking tape so he knew where to stand when he wanted feedback.

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Get yourself a Sustainer or Sustainiac, switch to harmonic mode and you'll be able to get feedback when playing straight to tape.

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Assuming you mean feedback from the amp, it has a ton to do with the amp circuit used. It is quite easy to make an amp oscillate. Usually this isn't preferred because it can be hard to control but I suppose with a properly designed amp and a bit of practice it wouldn't be too hard. The part of the amp that seems to have the most effect on controlling feedback is the the negative feedback. This is added to reduce distortion(which also reduces gain).

So first things first is to make sure you have a good amp to work with.

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You're confusing amplifier feedback, with feedback caused by resonating vibration in the guitar's body and strings when the amplified notes reinforce the vibrations. A clean amp with high damping can still cause guitar feedback, and be controlled by the player with a little bit of practice, which is what the OP was talking about. –  Anonymous Jan 24 '11 at 23:57
    
Um, no. In both cases it is due to the acoustic resonance GENERATED by the speaker of an amp. With a high gain amp it is much easier. The OP didn't mention anything about clean or distorted but gave references to people who use distortion. In both cases they are the same but my answer is more appropriate than yours w.r.t to the OP. –  Anonymous Jan 25 '11 at 0:59
    
BTW, a clean amp with too much "dampening" will not generate feedback. It depends on the amp, the guitar, the speaker, and the position/angle. But if you've every messed with high gain amps you will know how easy it is to get such feedback. It would be exactly the same with a clean amp but much harder. –  Anonymous Jan 25 '11 at 1:00

A lot of folks get their pickups dipped in wax to help control feedback.

Here's a link to Premier Guitar that explains how to wax pot your own pickups: http://www.premierguitar.com/Magazine/Issue/2009/Apr/How_To_Pot_Your_Own_Pickups.aspx

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You're talking about what a lot of us call pickup squeal, caused by the windings vibrating. That's not what the OP was talking about though. –  Anonymous Jan 25 '11 at 0:03
    
Potted pickups do indeed tighten th pickup a little, and the wax reduced the micro phonics of the coil--so if anything my intuition tells me that it would reduce the amount of feedback you receive (I need to research this claim). Also, I would really advise against potting your own pickups--especially if you have a nice set. I would hate to ruin a $300 set of Lollar Imperials, and most high end pickups already come potted--but the article is great if you want to experiment on a set of cheapies. –  Jduv Jan 25 '11 at 13:00
    
-1 Didn't read the question. –  Anonymous Feb 14 '11 at 17:12

The answer to a ton of the questions here so far are the same basics: practice and experiment.

In order to get feedback, all you really need is a loud amp and an electric guitar. Hollow or semi hollow guitars can be kind of hard to control the feedback, so definitely start with a solid body. The thing to experiment with is your guitar's position relative to the amp. Where you position yourself will change the frequency of the feedback you are getting. Moving the guitar around can change the note that's feeding back.

Some other hints:

  • Use some vibrato to help keep the sound "going".
  • Feedback is easier with a gain in addition to volume, so make it a bit dirty.
  • It's easier with a guitar that sustains well.
  • Compression will help you get some good feedback going, as it keeps your signal going for longer at higher volume (i.e. sustain).
  • You can use a wah pedal to control your feedback and the note that you are getting. Just slowly sweep through the wah's range and see how your note breaks up / feeds back.
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The amp doesn't even have to be loud. Creating a feedback loop is simply a matter of transferring the vibration from the guitar to the amp and back, and can result from touching the guitar's body to the speaker cabinet, effectively coupling the vibrations of the two. Then it's a matter of finding the resonating frequencies for the guitar; Hopefully they'll be in the key of the song. Sometimes they aren't, but when they are is when the fun happens. –  Anonymous Jan 24 '11 at 23:53
    
+1'Use some vibrato to help keep the sound "going"'. I think this is a real important trick. By keeping the string vibrating against the fret you can fine tune the pitch as the resonance sets in to find the right frequency. Even at low volume, with good compression and a sensitive guitar, you can get the right notes to grab hold. I was holding a conversation with mine feeding back as we talked over it one day. Made me love that particular guitar. –  Anonymous Jan 25 '11 at 0:07

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