Nothing is intimidating compared to show-stopping a guitar, screaming to hit notes to the audience while on stage on a live performance. Feedback is ideally unpredictable; therefore, to control it requires prior knowledge. High amplifier volume causes feedback, which may be undesirable. Controlling feedback to low levels ensures a beautiful volume comes up from the amplifier. Managing feedback, however, can be the hardest part. The primary goal of this article is to educate on how to prevent guitar amp feedback that may damage electronic devices, systems, and intended music performance objectives. Keep reading for more information.
What is guitar amp feedback, and what causes it?
When an electric guitar is plugged, its signal is amplified for enhanced hearing. When the amplified signal reverses to the guitar signal, it is also amplified in a constant loop. Then, it gets louder and louder and overloads the amplifier hence produce the loudest signal possible. When it happens instantaneously and continuously, it pierces and pains the ears. Guitar feedback happens quickly through gain-based effects such as overdrive, fuzz, compression, and distortion. The effects pick up low-level guitar signals amplify them, and as such, heard louder. This makes it simpler for external sounds to reverse into the guitar. The most feasible way of creating feedback is by tuning the amplifier volume up maximally. Different types of feedbacks get back into the guitar differently. Keep reading to find out.
Perceptibly, the guitar signal is created using fingers or a pick that vibrates the strings. The vibration leads to an alteration in the magnetic field of the pickup. The pickups then change the vibration tune into an electrical signal heard through the amplifier. Guitar pickups going “microphonic” is not a new term. In other words, it is when the poles of wrapped wires inside the pickups loosen and potentially vibrate. The amp speaker vibrates, creating waves that are heard. The noise cause sound waves that make pickup windings to vibrate. This is how simple the microphone works. When the pickups are microphonic, they act as a microphone for the sound waves in an enclosed place. When the pickup wires are pretty thin, they vibrate at a higher frequency, and this is the piercing squeal desired by most people. Pickups are dipped or potted in wax to prevent them from happening. When the wax ages or fades away, they break down, thus allowing the winding to loosen.
A few things can be done to get rid of this unwanted ear killing feedback. As aforementioned, pickups act as microphones but not great microphones. They cannot pick low-level sounds in enclosed paces or room besides anything with low-level clarity. High-level volumes are needed for the feedback to occur. The most probable fix is to turn down the amplifier and move the guitar far away. Keeping the guitar at a considerable distance ensures that the feedback waves weaken as they travel. Besides, it prevents sound waves from possessing enough energy when getting back to the guitar for feedback.
Microphonic feedback occurs as a result of high pitched sounds caught in loop feedback and amplified through the guitar repeatedly. Amplifiers have inbuilt EQ, and when high frequencies are turned down, they affect the feedback loop. Turning it down cancels out feedback frequency substantial boosts without losing the desired tones. Another way to suppress feedback is by the use of stompboxes that manage feedback automatically by mitigating feedback frequency with the amplifier EQ or lower the volume until when the feedback stops automatically.
The hollow body and acoustic guitars loaded with pickups are altogether monsters. They are designed in a way that makes their entire bodies vibrate and acoustically amplify the sounds. Specifically, acoustic guitars are renowned for being volatile feedback magnets. They have “Piezo” a pickup explicitly installed for stage use. The pickup is directly attached to the wood body and turns the body vibrations to the electrical signal amplifier. Their feedbacks are created similarly as electric guitars and have pickups explicitly designed to reproduce the vibrations. When controlling feedback with EQ or feedback suppressing stompboxes, treble and tone are lost.
The surefire way to handle these complications for acoustic guitars is by using a rubber soundhole mute that keeps the sound waves from entering the body and resonate. On the other hand, semi-hollow and hollow guitarists have resorted to stuffing the guitar body cavity with foam through F-holes.
However, harmonic feedback can be ear piercing, it entertains. The majority of artists use harmonic feedback as another tool in the shed. Harmonic feedback happens the same way as microphonic feedback but requires more volume to make it squeal to life. High volume makes the guitar strings vibrate.
How to prevent guitar amp feedback
Noise is something audio engineers, musicians, and live sound mixers are familiar with. It is the horrible, unwanted, and mood destroying screech that comes into play at worst possible times. Noise can be present at mid-ranged, nasal, low and humming, high pitched, and other myriad ways. Ideally, it is something undesirable and is generally unwanted in the overall sound. In the guitar realm, it comes as a result of electromagnetic interference (EMI). The EMI interacts with many amplifiers, pickups, cables, and many other electronic equipment when connected to a guitar amplifier. Feedback, therefore, can be controlled or tamed in a range of ways. Here are some of the ways.
By use of noise suppressor pedals
When a guitar picks up strange interferences at different venues which are amplified into noise, when the hiss from gain peddles and amplifier’s preamp causing songs infernal roles and uncontrollable feedbacks, all these problems are caused by overdrive, distortion and fuzz effects. Noise suppressor peddles the real problem solvers that detect the source of such incoming noises. Therefore, noise suppressor peddles are essential guitarist tools used to create dramatic pauses in songs. Noise suppressors, also referred to as noise gates, are handy emergency devices used when guitarists play different venues, each coming with their unprecedented electrical problems. Badly set public address systems, electric generators, and cheap LED screens potentially feed nasty noise interferences, thus giving a show an uncomfortable onstage experience. Noise pedal suppressors will assuredly offer perfect solutions to such nasty situations.
The hissing sound, a noise suppressor pedal, is meant to control originates from the amplifier at around 60Hz. The other type of noise is the white noise that comes from too much gain pushed into the amplifier through the distortion and overdrive pedals.
By use of Acoustic guitar feedback suppressors
Feedback suppressors are audio signal processing devices. They are used in live sound reinforcement systems to deter or suppress unwanted audio feedback. For feedback suppressors to control feedback, they use three methods, namely:
- Adaptive filtering
- Automatic notch filtering
- Frequency shifting
Frequency shifting: is the oldest suppression method historically traced back to the 1960s. Frequency shifting works by the introduction of varying shifts in frequency to the response of the system. A frequency mixer is used to implement the varying shift frequencies. Through frequency shifting, modest improvements in gain feedback are attained and create a noticeable pitch music distortion program. The adaptive filter methods, on the other hand, works by modeling the sound transfer reinforcement system and subtracts the reinforced sound from the system inputs, just like echo cancellers do when removing echoes from communications systems. Notch filters and parametric equalizations are mostly used by sound engineers to control feedback manually. Feedback suppressor applying automatic notch mechanism listens for onset feedback and inserts a notch filter automatically to the signal path at the deleted feedback frequency. Feedback suppressors use a myriad of techniques in sensing feedback from non-invasive harmonic analysis. The automatic notch method is the most influential and is advantaged since sound is not colored until the system is vulnerable to feedback.
Will a noise gate stop feedback?
A noise gate is a software or electronic device primarily used to control audio signal volume. Noise gates are comparable to compressors that reduce above-threshold signals such as loud attack musical tones. Noise gates nonetheless overcome signals of a certain range. They allow only the main signals to pass when the above-set threshold. Signals below the threshold as such as denied access. Noise gates close and open, depending on the noise threshold. When sound is above the threshold, they open, and when below the threshold, they close. Notably, noise gates do not remove unwanted noise from the signal itself as when they are open, both unwanted noise and signal pass through successfully because the sound is unnoticeable. Unwanted noise is detected in the absence of the primary signal, such as a guitar solo bar. In a nutshell, the primary function of noise gates is to eliminate sounds below the set threshold. They are primarily used in recording studios and sound reinforcement systems. Rock music also uses portable stompbox units to manage unwanted sounds generated from guitar amplification. Additionally, badly limited noise gates are used to eradicate audio recordings, unwanted noise by blocking frequency bands.
How to control feedback on a guitar
Guitar feedback can be controlled using the following methods:
Changing equipment levels
Turn down guitar or amplifier gain: indubitably, high guitar gain is the primary source of feedback. Higher amplifier or guitar gain levels create feedback.
Reduce guitar volume: tune down the guitar volume using the guitar knob and the amplifier at the same time. This upsurges output, at the same time, reducing input that prevents feedback. Always ensure the amplifier volume is low, as this will restrict instant feedback.
Turn up bass and lower the treble: Low bass and higher treble create feedback. When playing music, ensure the sounds are robust to eliminate any feedback. This can be tested by playing guitar notes at the same time adjusting each of the knobs separately.
Proper positioning of the amplifier is the primary way to prevent feedback as it ensures microphones do not pick unwanted sounds from the amplifier. Move tables and chairs to eradicate reflective sounds that possibly sound back to the input.
Move away from the amplifier: the inputs can pick sound waves generated from the amplifier; therefore, it is advisable to move away from the amplifier. Ensure the amplifier is in front of you, as this will ideally help reduce feedback on those on stage. Purchase more extended chords that give room and freedom of movement.
How to get guitar feedback at low volume
Without a doubt, when the guitar is close to the amplifier, you must get feedback that will cause the guitar strings to vibrate. To ensure feedback is at the lowest volume, put a high gain distortion pedal between the amplifier input and the guitar output. This adds necessary saturation and compression to the guitar signal to ensure it sustains for a longer time and the strings to have enough vibration time while responding to the amplifier sounds. Besides, it will help to get the guitar close to the amplifier speaker. Additionally, low feedback volume can be achieved by putting a guitar headstock against the speaker cabinet side. It is not easy to get controllable feedback at bedroom levels. However, with adequate amplifier gain and close proximity, manageable low volume is achieved. Consider turning the pedal on while in need of feedback and turn off when not necessary.
Feedback is always undesirable, especially when it occurs to a singer in a public performance using public address systems besides spoiling the show by producing ear-piercing sounds. To control this unwanted sound, detection devices are required. The research done and presented by this article is substantial to help deal and manage unwanted sounds in music that may end up spoiling electronic devices and systems. Various ways and strategies have been championed on how to reduce and control feedback. The article has as well analyzed the multiple types of feedback and how they occur besides their prevention methods. Read and implement for comfortable music that is ear-friendly.