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How to control feedback from an amplifier

Rating: 0 user(s) have rated this article Posted by: leokisomma, on Feb 27,2012, in category Gear Related Views: this article has been read 8338 times
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How to control the feedback from your guitar

Okay, so you’re obviously aware that sometimes if you are playing your guitar through the overdrive channel of your amplifier, and that it mostly seems to occur once you use a certain amount of gain and/or volume but you don’t know how to keep it under control. Well, I’ll do my best to help you in this lesson.

Some people will use noise-gates to help reduce feedback which does work to a degree, but bad notes still have a chance of ringing out, and noise-gates can take some of the ‘meat’ out of your tone if you set them up wrong.

Firstly you will need to understand the difference that gain and volume makes to the signal from your guitar. Because a guitar’s pickups are always close to the strings, and are made of constantly over-wound coils of metal wire, they have a much higher output than say a microphone. This means that if you turn the volume of your amplifier up or down, it will make much more of a difference to how loud your guitar sounds compared to changing the amount of gain, which will make a slight difference to the volume, but mostly just changes the sound coming from your amp.

You must be aware that both of these will contribute immensely to the amount of feedback from your guitar, and so will the volume/tone dials on your guitar. If you turn down the volume on your guitar, you will start to find that the gain seems to become slightly less pronounced; this is because gain essentially makes the signal bigger as it reaches your amp, so giving it less signal to work with will therefore also reduce the effect that gain has on your overall sound.

Many guitar players I’ve seen have the problem of constant squealing when they either stop playing momentarily or accidentally miss a note. This is most easily remedied by turning down the volume dial on the guitar slightly, as this makes the entire signal smaller. Also, they are sometimes unaware of what effects certain effects pedals are having on their sound. There are 2 types of pedal that really alter feedback from your amplifier: overdrive/distortion and compression.

The difference between distortion and overdrive is that an overdrive pedal is built to sound like and amp’s own overdrive channel, whereas distortion pedals are in general much more aggressive and “metal” sounding. Both of these types of pedal will be changing the gain and volume of the signal passing through them while they are activated. This means that you may have to change the settings on your amplifier or pedals to compensate for this; e.g. if you are mostly relying on the distortion from your pedal because you’ve got an amplifier from a maker like fender which doesn’t focus on the overdrive channel much, then you would need to turn the gain on your amplifier lower so that the pedal dominates the sound coming out, but if you just want a pedal for an extra kick during a solo, then you would turn the gain up on the amp, but turn the gain on the pedal down while turning the volume on the pedal up. This will likely make your guitar sound more powerful due to more signal passing through it, and possibly cause it to become slightly louder as well; you will have to adjust the volume/level dial on the pedal to your preferences when using it like this

Compression pedals are a mystery to most people who haven’t used them, but their effect is fairly easy to explain initially. What a compression pedal does is compress the signal of your guitar (you don’t say?) so that the louder notes you hit are slightly quietened down while the quieter notes are made louder. In essence a compressor pedal makes most of the notes you play sound like they are the same volume. Some players don’t like using compressor pedals because they prefer to be able to make notes sound louder and quieter, which is understandable, but there is another consequence of this effect that leads directly to the amount of sustain your guitar has.

If all the quieter notes are louder, then they will ring out for longer. This means that if you were to hit a note and then try to hold it and keep it going, you are likely to hold it for longer if you have a compression pedal set up. Feedback will be increased as some of the quieter sounds you are making are being boosted so they contribute more to the signal reaching your amplifier.

There is also something that a lot of people don’t realise about tube amplifiers and in fact most other amplifier types as well. If you turn the volume of your guitar amp up, the gain will also slightly increase as well, without you touching the gain dial. This means that if you play with the same settings at a higher volume, your guitar will sound more distorted and you may have to turn down the gain dial to retain your sound.

Now it’s time for the trick you’ve been waiting to hear about: the ‘endlessly sustaining a note’ trick.

As I’ve said earlier, many guitarists will use things like compression and overdrive pedals in order to boost the amount of feedback that they have, making it more likely that feedback will kick in. Really though, the best thing to do with this technique it to turn your amp up louder, as this is a mostly volume reliant technique, and standing closer to your amplifier will also increase the resonance between your guitar and the cabinet, further increasing your chances. Obviously this technique isn’t solely relying on gain, as Gary Moore had comparatively little gain for his parisienne walkways long note, but the more gain you have the more likely you will get this feedback. There’s a reason why you don’t get feedback on the clean channel of an amplifier very often.

From personal experience I know that this trick is massively dependent on the guitar that you are using and the pickups in that guitar as well. I always use passive pickups as opposed to active pickups. If you need more info on the difference then look for the user Fenderexpx50 on this website, as he has written an article (Active and Passive pickups) on the difference between them. Now I generally use pickups such as Seymour Duncan Humbucker hotrods, or Dimarzio D activator Humbucker pickups which are with the exception of one other pickup are the most powerful passive pickups on the market today. This means that I have a lot of signal passing back to my amp for when I need that ‘endless’ note. You can still get this with passive pickups but there is a tip I can give you with any guitar to improve the feedback. Switch to the bridge/treble pickup, as this will be picking up more of the high end sounds your guitar makes, making feedback much more likely.

Aside from this there are various ways that you can get feedback in the studio, but you really need to get the effect live as well, so don’t become too reliant on techno-wizardry for your sound.

That’s pretty much it for this lesson. I hope it’s helped some of you out there in your quest for some extra feedback.

Take care guys and I’ll see you next time! 

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