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Controlled Feedback - Is there a certain required decibel level to get it?

Messages
537
I love the sound of controlled feedback in a guitar solo. Is there a general minimum decibel level required?

I know that where you stand in relation to the amp, how your guitar is constructed and other factors play in but I always thought it had to be super loud until I saw a guy get feedback on a little Fender Vibrochamp XD.

Below is a clip from a band called Dream Theater. If you look at 0:59 - 1:15 you will hear what I am talking about.


Thanks.
 
Messages
537
No specific dB required, just dB relative to distance from the amp based on the characteristics of the guitar.
I remember watching a Ted Nugent show in which he put an X on the stage floor where he was looking to get good feedback.

So from what you are saying, I need to experiment with different distances from the amp and guitar angles. I don't necessarily have to crank the amp way up to high volumes. Thanks!
 

tenchijin2

Member
Messages
3,030
It helps to understand what "feedback" is. The term feedback is used in processes to define a situation where the result of some action is "fed back" into the process to change the process. In simple amplification terms what that means is that the sound projected from the amp causes the guitar strings to vibrate, which in turn causes sound from the amp, which then causes strings to vibrate, and on and on. The critical point in this case is that the sound from the amp has to make the strings vibrate.

If the amp is very quiet, there's not enough energy to vibrate the strings. But the energy is greatest near the amp no matte what volume you're using, so as you get closer to the amp you increase the odds that feedback will occur at ANY volume. And yes, position matters too because it determines the way the strings interact with the sound waves. As you increase volume from the amp, you can increase distance from the amp to get feedback. As you decrease volume, you must get closer.
 

dewey decibel

Member
Messages
10,855
I've gotten it at pretty low volume levels. Along with what everyone's mentioned I think EQ plays an important part, that's why some notes jump out right away and others are a bit more finicky. But I have certain combinations of gear- like this guitar with this pedal, that make it really easy.
 
Messages
7,234
As mentioned, there are a lot of factors involved. Importantly, any electric guitar will have a few notes that are more resonant than the rest, and more likely to feed back controllably at a lower level than others. After guitar liveliness (particularly in the neck), the amp type, tone, amount of gain, speaker type & position relative to the guitar are the most important, along with the character of the soundspace. Light strings feed back more easily- it takes less ambient energy to make 'em move.

Given a lively guitar, a rig with plenty of gain, and proximate placement, you can get good sounding octave feedback at a level low enough to talk over if you pick the right note. I used to do it in the living room with my H&K Cream Machine and that only puts out a couple of watts.

Back in '79-80 I was playing songs that required repeatable harmonic feedback on several specific notes and I used to do the same trick of marking a spot for each one on the stage when we did soundcheck. Later during the show I'd go to the mark and get the right sound every time. At smaller gigs we'd be playing more quietly on a stage with less room to move and this wasn't always easy. So I took to using a different cab for problem stages- instead of having my Marshall 4x12 behind me I'd use a small 1x12 on the floor facing up at my guitar, placed off to stage right or out in front by the floor monitors. This arrangement helped immensely and allowed precise feedback at reasonably low volumes night after night, regardless of the venue. (We'd still put the 4x12 up but it wasn't plugged in, basically just a fancy stand for my head.) The little cab had an EVM instead of my usual Celestions. That worked out well: it had a less-piercing tone when facing right at me, and the EV was robust enough to handle knocking around in the truck when it wasn't used, while being virtually unblowable for when it was. Plus, we always had it with us if a spare cab ever was needed, and sometimes it was. The thing was still pretty bright; on really small stages I'd throw a T-shirt over it to save us from getting drilled. The right feedback was there for me every time though.
 

Phletch

Senior Member
Messages
9,896
Just to echo what's been said and confirming my own observations on this phenomenon, it's a combination of volume, proximity and orientation of the pickup(s) to the speaker(s), and the harmonics of certain frequencies that, given the other factors, are more resonant than others. If there's enough volume, I can get it with a totally "clean" amp. I've also found that semi-hollows lend themselves well to controlled feedback (and, if you go "too far" it can get uncontrollable very quickly). My current set-up of an Epi Dot with DiMarzio 36ths into my Mesa Mini Rec using low gain/high volume is just wonderful. Just about any note, any distance to the amp, using either pickup, I can just let that note ring and hold it virtually forever if I want, and just control it either by turning into or away from the speaker and/or rolling the guitar volume around. It's a nice tool to have in the bag.

This is one of my favorite clips of somebody artfully using controlled feedback - Steve @kimock , with dual Boogie Mark Is. Maybe he'll chime in with some details about how the amp was set, etc., but this was over 25 years ago, so we'll cut him some slack if he doesn't :p.
 

kimock

Member
Messages
12,520
Just to echo what's been said and confirming my own observations on this phenomenon, it's a combination of volume, proximity and orientation of the pickup(s) to the speaker(s), and the harmonics of certain frequencies that, given the other factors, are more resonant than others. If there's enough volume, I can get it with a totally "clean" amp. I've also found that semi-hollows lend themselves well to controlled feedback (and, if you go "too far" it can get uncontrollable very quickly). My current set-up of an Epi Dot with DiMarzio 36ths into my Mesa Mini Rec using low gain/high volume is just wonderful. Just about any note, any distance to the amp, using either pickup, I can just let that note ring and hold it virtually forever if I want, and just control it either by turning into or away from the speaker and/or rolling the guitar volume around. It's a nice tool to have in the bag.

This is one of my favorite clips of somebody artfully using controlled feedback - Steve @kimock , with dual Boogie Mark Is. Maybe he'll chime in with some details about how the amp was set, etc., but this was over 25 years ago, so we'll cut him some slack if he doesn't :p.
That's all about the acoustical superiority of polyester.
 

9fingers

Silver Supporting Member
Messages
7,960
A semi hollow gets "excited" more easily with less amp volume. Also getting the amp on a stand pointing right at the guitar helps the process.
I'll have to try that polyester magic!
 

AdmiralB

Member
Messages
3,060
Pickups can also 'hear' the amp, depending upon how microphonic they are. With enough gain, you can get feedback at bedroom volumes, sometimes less, when there's no way there's enough volume to excite a body. I remember when I got a Foxrox ZIM pedal, I was recording a demo using the pedal into a Yamaha DG Stomp set to a clean, Fendery tone, and I got feedback on a few notes...

...wearing headphones. No amp at all.

When modelers were newish tech, they didn't do harmonic feedback very well; the original Axe-FX was the first one I used that could do it, and even it wasn't what I'd call great. The Axe II was, again, the first I used that did it as well as most amps. Prior to that, when I would record using a DMA and I needed feedback, I would split my signal into a Boogie Mark III set for insane gain, and let it kick the feedback off.
 

sws1

Member
Messages
12,084
In one of the songs I play with my band, I actually control the feedback with the wah pedal. i.e., I'm using the wah during the solo, hold a note, and then adjust the wah to get the feedback to come in/out. It's tons of fun. Don't know if the drummer likes it, since my amp is usually right next to him.
 






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