How Does A Guitar Amp Work? A Guide You Can’t-Miss!

a guitar player trying to understand how his guitar amp works

If you’re a guitarist who’s curious about how guitar amps work, then this article is for you! We’ll cover everything from the basics to some of the latest advances in amp technology. We also discuss other essential gear for your guitar tone and how to choose what is suitable for your amp. Once you master your amplifier, you’ll be one step closer to guitar mastery. Enjoy!

Amplifiers – Form and Function

From the outside, amps look like speakers with a few dials to adjust the sound. Internally, however, there is much more going on, as explained below.

Function

Guitar amplifiers amplify the signal that comes from an electric guitar or bass guitar. When you play an electric guitar or bass without plugging it into an amplifier, the sound produced by the instrument is almost inaudible because the signal is too weak.

Plugging the guitar directly into a speaker would result in a noisy and weak sound. Speakers are not designed to take tiny signals as input. So before the input goes into the speaker, the signal has to be boosted. Also, the signal from the guitar can quickly encounter interference/disturbance and hence has to be strengthened. An amplifier does precisely this.

An amplifier boosts the signal coming from an electric guitar and makes it strong enough to resist interference. This makes the signal ideal for plugging into a speaker to get a loud and clear sound.

Amplifiers also add their own flavor or character to the sound of the guitar. This is because the signal goes through the various amplifier stages and comes out with a different sound signature.

Basic Circuit

The basic flow of signal in the case of an electric guitar and amplifier is:

Guitar -> Preamp -> Power Amp -> Speaker

The weak signal from the guitar goes into the preamp, where it is given an initial boost. The preamp modifies the input and imparts a distinct character. Then the partly boosted signal goes through a power amp, further increasing it to greater amplitude. Finally, the amplified signal is sent to the speaker to produce the sound.

Preamp

Preamps are the part of the amplification process that adds effects and brings the signal to ‘line level’. They often have tone controls, volume controls, gain, various channels, and EQ controls. Preamps also have knobs for boosting or silencing specific signal frequencies, most commonly treble, mids and bass.

Base, treble, and mids need to be controlled because our ears are more sensitive to middle range (middle of our human hearing range) frequencies. This means that mid-range sounds are perceived to be louder, while bass and treble may lag behind.

The placement of tubes (or valves) is best at the preamp level in modern setups, as this stage affects the sound the most. Hence, tube preamps are more influential for sound than tube power amps if you seek a vintage tone.

Power Amp

The power amp provides the most significant signal boost in the amplification chain. It also changes the signal to make it more ‘speaker friendly’. Speakers are designed to work with much larger voltages than the guitar can produce, making it imperative to change the nature of the current passing through to the speaker.

Power amps may sometimes have some tone controls like presence or resonance, giving them some influence on the sound. You can get an all-tube power amp, but it would make a very subtle difference in tone. Since tube amps are expensive, it may not be an ideal choice for everyone.

Speaker

Speakers, as you may know, convert the electrical signal from the amp into sound. It is essential to choose the correct speakers for your amplifier, considering the amplifier’s ability to supply power. Incorrect speaker and amp matchups can destroy or shorten the equipment’s life and ruin the sound.

Of course, it is essential to judge the sound quality the speaker has to offer and its matchup with the amplifier. The size of the speaker would depend on the use case. Most amps come with a built-in speaker that is generally self-sufficient for personal use. For professional use, however, bigger and more powerful speakers are necessary. Larger speakers also sound different as they impart unique sonic characteristics. 

Another factor that influences sound is the stereo setup. Multiple speakers, strategically positioned in different places and playing different channels, feel ‘larger’. Various speakers may also have tonal characteristics that impact your guitar tone, so choose wisely.

Choosing The Right Speaker For My Amp

Speakers should be chosen according to the amp’s ability to deliver power at the speaker’s impedance. To get a better idea of what you need to look for, check out an Orange Crush 20 Amplifier review we wrote not long ago. If you’re into Fender, here’s the Fender Champion 20 review.

For instance, an amplifier delivers 1200W at 4 Ohm, and the speaker has an impedance of 4 Ohm but has an optimum power range of 400-800W; the amp may be producing too much power for the speaker.

When using multiple speakers, the impedance must be calculated based on the circuit diagram resulting from the connections. Unlike resistance, impedance is frequency-dependent and is not calculated using a simple middle-school Physics formula. This is where things can get complicated for beginners. Here’s a short video that’ll help you figure it out:

https://www.youtube.com/watch?v=6B0OlQaD_i4

Speaker Cabinet

Speaker cabinets make a surprising impact on a guitar’s tone. The material, thickness, size, baffle (front face of a speaker), and speaker cabinet design all contribute significantly to sound.

Speaker cabinets are generally designed to be acoustically inert. This means a good cabinet distorts the sound as little as possible. This is usually achieved by using nonresonant materials such as wood or really thick material to absorb any stray sound waves. All sound must be from the front of the speaker. All other sound waves are suppressed.

From its shape to whether it is sealed or ported, the cabinet’s design also contributes to the tone. The baffle’s shape prevents the front and rear sound waves generated by the speaker from interacting and canceling out.

There are a lot of different speakers to choose from. The final decision depends on your budget, preference, and compatibility with your equipment.

Microphone

Anyone who has ever recorded audio of any kind understands that mic quality and positioning can make all the difference in clarity and tone. Various mics are available, but generally, any good quality ribbon, condenser, or dynamic mic would perform well. However, aside from quality, the mics would differ significantly in the resulting tone.

Dynamic mics are ideal for recording guitars since they are very tolerant of loud sound. Condenser microphones, however, are more sensitive and suitable for getting all the finer details of a tone. Ribbon mics are the more traditional choice and are an old but excellent technology. They are known for recording sounds closely resembling what a human ear would hear.

Some commonly used microphones for recording guitars are:

  • Shure SM57 Dynamic Mic
  • Baby Bottle SL Condenser Mic
  • Royer Labs R-121 Ribbon Mic

While choosing a mic, you may want to refer to its frequency response. The frequency response would determine what range of sounds the mic is ideal for.

Mic positioning can create directionality. It can help channel different parts of a music piece into their own distinct ‘pockets’ in a mix by having a separate mic assigned to each element. Not just positioning the mic in the room, but even inches from the speaker, minor adjustments to the mic’s position would change the resulting recording significantly.

Tube Amplifiers

Tube amplifiers use induction through vacuum tubes to amplify the signal from a guitar. They are the oldest amplifier type and often use primarily analog components. However, modern tube amps may have some digital elements to add stability and durability to the system.

History

The first production dedicated electric guitar amplifier was launched by the Electro String Company in 1932. Back then, amplifiers for music already existed but were not completely committed to the task. The amplifiers designed for radio and PA were not enough to amplify guitar sounds. They were large and bulky and ran on battery power.

The Electro Strings model was later modified by the company’s engineers to generate more power as musicians demanded for louder systems. This started a race among musicians to be the loudest and meanest, a trend that continued into Rock ‘n’ Roll and then Heavy Metal.

In the 1960s, guitarists realized that pushing a tube amp beyond its limits led to distortion, and they liked the sound of it. This led to the birth of distortion as an intended effect in music. Today there are thousands of distortion pedals and effects used in various genres, all birthed by the iconic sound of tube amps.

Modern Role

Modern-day tube amps may or may not be 100% analog and hand-wired. Regardless, they carry on the baton with their characteristic warmth. They are used in genres such as alt-rock and other genres that need clean or semi-distorted guitar sounds.

There are generally two types of tube amps, Class A, and Class AB. They differ in how the tubes are biased and whether they work in pairs. In Class A, the tubes are biased such that they are always on at full capacity, even when there is no signal running through them. Class AB amps have tubes that run partially when there is no signal, and the tubes function in pairs.

The two types of tube amps differ in their tonal characteristics, response, feel, and efficiency, and you may have to try them out to know what is best for you. The transformers of tube amps also have their own tonal signatures and saturation characteristics.

Advantages Of Tube Amplifiers

  • Desirable tonal qualities like richness, dynamic response, sustain, harmonic content, and a more gradual and gentle clipping leading to the signature distortion.
  • Tube amps are louder than solid-state amps of comparable builds.

Disadvantages Of Tube Amplifiers

  • Larger size and more weight
  • More expensive
  • High maintenance
  • Vacuum tubes are fragile, and they wear out over time, and their tone changes, leading to inconsistencies and unreliability

Examples

  • Blackstar HT Club 40
  • Harley Benton Mighty-15Th
  • Fender Blues Junior IV

Solid State Amplifiers

Solid-state amps use transistors to amplify sound. Technically, all amplifiers that do not use tubes fall into this category, from amps that use digital components to emulate tube amp characteristics to entirely virtual amps (software plugins).

History

Solid-state amps first became prevalent in the 1970s. With advancements in transistor technology, amps could be made in solid-state without the need for less reliable and bulky vacuum tubes. Though these early solid-state amps did not sound the same as tube amps, they were cheaper, lighter, and easier to mass-produce.

The solid-state amp made music more accessible to millions of people as they were more affordable. They also did not need frequent valve changes or biasing to function correctly. Although they lacked the signature warmth of tube amps, they had their own characteristics, such as consistency and faster response.

Role

Solid-state amps today can be used in practically all genres of music. This is because they can be designed to replicate a particular sound or make a unique sound. Initially, they were used in genres such as Jazz and Metal for their consistency and quick response.

Advantages Of Solid State Amplifiers

  • Lighter, smaller construction
  • More affordable
  • Transistors last for decades and hence are low maintenance and highly reliable
  • Consistent sound
  • Quicker response

Disadvantages Of Solid State Amplifiers

  • Lack the spontaneity and organic sound of tube amps
  • Less volume than tube amps
  • Lacks the signature warmth of tube amps

Examples

  • Orange Crush CR120C
  • Roland JC-22 Jazz Chorus
  • Fender Tone Master Deluxe Reverb

Digital Amplifiers

Digital amplifiers use neither tubes nor transistors for amplification. Instead, they use pulse width modulators for amplification. These are by far the most versatile type of amplifier, with the most compact design.

Role

These are not industry standards yet and are used by a smaller number of professionals, but they are gaining traction. The convenience of an amp head in the palm of your hand will undoubtedly be a popular choice in the digitized music industry.

Amps can also be entirely virtual. They can be in the form of software that you feed your guitar signal into via an audio interface, and you get your output in a Digital Audio Workstation. This audio can be edited and then rendered to play on a speaker.

Digital amps offer better options for integration into modern-day music production pipelines, with more ease of use and integration with MIDI. They are also generally more affordable and low maintenance.

Advantages of digital amplifiers

  • Small size and light build
  • Great stability and reliability
  • Higher fidelity
  • Input and output impedance can be regulated

Disadvantages of digital amplifiers

  • Reduced gain
  • Lacks organic tonality

Examples

  • Fender Tone Master Deluxe Reverb
  • Blackstar Silverline Stereo Deluxe
  • Kemper Profiler

Hybrid Amplifiers

Hybrid amps combine solid-state and vacuum tubes. They either have a tube-based preamp and solid-state power amp or the other way around. Although there are tube-based amps with partial solid-state features, they are still not classified as hybrids.

Hybrids try to offer the tone of a tube amp with the modern-day reliability of solid-state. Hybrids vary significantly as there are many permutations and combinations of designs possible. Generally, the best combo is a tube preamp and a solid-state power amp. This gives the advantage of a warm, tube-like tone.

Role

Hybrid amps are similar in approach to hybrid cars, aiming to get the best of both worlds. These may be used in case the artist likes the tone of tube amps but does not want to spend money replacing and biasing tubes as often as with a 100% tube setup. It is more of a practical middle ground.

Advantages Of Hybrid Amplifiers

  • High Efficiency
  • More reliable than a traditional tube amp
  • Has the tonal characteristics of a tube amp, with the convenience of a solid-state amp
  • No need for output transformers in the case of a solid-state power amp

Disadvantages Of Hybrid Amplifiers

  • Have some of the disadvantages of tube amps due to the hybrid system and use of vacuum tubes
  • May sometimes be unwieldy systems due to the mixing of different technologies.
  • Lack of output transformers leads to the absence of the tonal characteristics that they add.

Examples

  • Vox VT40X Modeling Combo Amp
  • Line 6 DT25

Which Amplifier Is Best For Me?

To pick your perfect amp, trial and error is the most practical approach, with a healthy mix of advice from professionals. Of course, this does not mean you need to buy amps to try them out. You should always try out equipment at a shop before buying it to get a taste of what it can do.

You can also try out equipment by borrowing or renting and make sure to talk to the owner about their experience with the gear. If you’re confused about which type of amp you should get, this video may help:

https://www.youtube.com/watch?v=qRvRZNg8L0w

Finding your perfect match might take both time and insight into what sound you crave the most – from your playing, and to match the feel/theme of your band and live gigs.

Some Misconceptions About Amplifiers

The guitar player community is riddled with strange misconceptions about amps; some of these are:

Do I need an expensive vintage amp?

The short answer is No; many modern-day solid-state amps feel and sound very similar to tube amps. Even affordable models can have great sound. You just have to look out for them.

Solid-State Amps Suck

No, they don’t. Solid-state amps have come a long way since the ’70s. As explained above, solid-state is highly advanced and versatile; give it a try.

All tubes sound the same

No, all tubes are absolutely not the same. Different brands and models have distinct tonal characteristics and use cases. Be aware.

Tube brands determine their quality

All existing tube brands make batches of both excellent and not-so-great tubes. Buy your tubes from a reputed buyer and not from random eBay hustlers (where you may get a fake tube too).

Biasing is a waste of time

No. Biasing is essential for the longevity and functioning of your tubes. Get it done by a professional each time you replace tubes.

Tube amps must be 100% analog

Tube amps that derive their sound from tubes and also use more contemporary components are almost indiscernible in tone from 100% analog ones. It is a matter of taste and convenience.

The Effect of Tone on the Guitar Player

You’ve probably heard that ‘tone is in the fingers’, but have you ever considered the effect of tone on your guitar playing? 

A good guitar amplifier’s “signature sound” can imprint itself onto a player’s sound and dramatically alter the way the guitar actually feels under the player’s fingers. The amplifier has to make the guitar sing. It has to bring out the very best in every guitar playing session.

The role of the amplifier is as important as that of the players themselves. Without a good tone, you may not feel confident in your playing either. 

Finding a guitar tone that suits you or the kind of art you want to make is a deeply personal endeavor. There is little reason to claim that one type of amplifier, or any other piece of gear, is better than the other when guitar tones are all largely subjective. Enjoy your path and let others do the same!

I hope this article helped you with your lifelong musical journey. Have fun jamming out to your favorite songs! 

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