A Fender friend reached out the other day and asked if there existed a dictionary of guitar amp terminology. He wanted to learn more about the technical side of guitar amps and was looking for explanations of all the semi technical-musical terms that are thrown out in media, on internet communities and in guitar shops. 

Most players love talking about tone and gear. While gear is somewhat tangible, tone is abstract and very difficult to describe precisely in words. Not only do we lack a common and objective vocabulary, we all have our own personal taste which complicates things even more. We misunderstand each other all the time. Let’s look at a few examples: 

• A stratocaster played in the in-between pickup positions 2 and 4 definitely sounds “quacky”. What is then “sparkling” and “edgy”. What about “Smooth”, “mellow”, “muddy” or “woody”? What’s the difference? We all know humbuckers are smoother than single coils. But when are they too muddy, and what exactly is “muddy”? 
• Loud, full, efficient or powerful speakers. What is the difference? 
• Hot pickups? Sweet spot? Vintage tone? Haha… the discussions that ever end. Luckily, fenderguru.com is here shed some light in the dark, provide clarity where there is confusion and, as always, try to explain things from a musician’s perspective. Techs don’t need any advice. They already know it or are too stubborn to change or learn something new. 

The best way to describe tone is using concrete and specific examples that we all can refer to, like a specific song on an album, a specific guitar, specific pickups, specific amps or speakers. Tone is always best described as “compared to what”. The more guitars, pickups, pedals, amps and speakers you have played, the bigger bank of concrete reference tones. Experimenting with lots of gear is also an essential part of learning how to pair the right guitar with the right pedals and amp and finding your tone.  

Let’s look at a few commonly used technical and musical terms. This is relatable with both vintage amps and other amps. Please feel free to add more definitions yourself in the comment field or request an explanation of more terms. We will try to append it to the list.  

Speaker efficiency

Also known as “sensitivity”. Explains how much bang for the buck you get in terms of output volume and input energy. You measure the volume from the speaker in dB given a fixed input signal at a certain wattage. If you feed the speaker with a 440Hz (A tone) sinus signal at 1w, you can measure the loudness using a decibel meter at a specific distance. The standards for measuring efficiency were established in the early days of the loudspeakers. With modern, new speakers the values are fairly comparable between different manufacturer brands. If you have old speakers from 1950-60s their 95 dB/w will most likely not be as loud as a 95 db/w speaker from 2019. This is explained by both different measuring techniques and speaker magnets getting gradually weaker. 

Speaker power 

Explains how much power a speaker can handle without getting physically damaged, mostly a burned coil wire or torn paper cone due to large cone vibrations. Power and Efficiency is not the same. A very powerful speaker is usually not very efficient. The stiff cone and heavy and large coil require a significant amount of power to start vibrating. Back in the early amp days only a few speaker brands and models like JBL and EVM could deal with high power above 50w. They were both expensive and heavy. Since the late 90s lots of powerful speakers became available from many manufacturers and they are not necessarily expensive. The most common mistake people do is looking at power rating and/or efficiency to judge whether a speaker fits your needs. The frequency response, magnet type, construction and cone type/design are the important factors. There is a lot more to speakers that is not possible to quantify as numbers to be put on paper. You need sound clips and descriptions from people that you can trust, tone-wise. 

Speaker impedance

Impedance means resistance, but is technically measured across a wide frequency range. The tube configuration (tube type, number of tubes in parallel or series) and output transformer has to match the speaker impedance in an amp. In Fender amps it is generally safe to stay in the range between half and double impedance. This means that a 4ohm amp, like the Pro Reverb, can be run in the 2-8 ohm range. An impedance mismatch will result in less clean headroom and sometimes shorter tube life.  

American vs British speakers

Vintage Fender amps were loaded with Jensen, CTS, Oxford, Utah, JBL. These speakers are transparent, bright and naturally sounding. The term American-style speakers is used to describe speakers that can deliver a bright, clear and sparkling Fender tone. On the other hand, British speakers are traditionally more mid-focused and mellow with less sparkle, typically (British) Marshall amps with (British) Celestion speakers.  

Sweet spot

The breakup point of a tube amp, where clean tone meets distortion. The sweet spot is more a range rather than a specific point. Be aware of that people have different understanding of “clean tone”. For me personally, Robert Cray’s strat tone with big Fender amps like Super Reverb and Vibro-King is the definition of “sweet spot”.  

Sag

The effect “sag” happens when an amp is struggling and pushed beyond its sweet spot. It is also known as compression. Sag happens when the DC power amp circuitry, involving the rectifier, power transformer, DC and filter caps and cathode caps (if the amp is cathode bias), struggles to deliver enough current fast enough to the power tubes. It can also be caused by the output transformer sitting between the tubes and speakers, especially if the transformer is too small to handle the energy it is delivered. Instead of a linear, hard and mean attack you will experience a softer and “saggy” response if you dig hard into the strings with a pick. A good example is the two dual 12″ amps Pro Reverb and Twin Reverb where the huge transformers, diode rectifier and 4x6L6 of the Twin has minimal sag. Sag is an important element of good tube amp tone and is one of the key characteristics of tube amps. Transistor amps do not sag that much unless they are built to create synthetic sag (i.e. digital amps where sag is created synthetically with advanced signal processing). One way to change the amount of sag in tube amps is using different rectifier tubes. A diode rectifier (not tube!) has the least amount of sag and will deliver a high output voltage with little/no loss. The plate voltages on the preamp and power tubes are therefore also high and allows more voltage gain and power amplification (=more headroom). GZ34 provides a high output voltage while the 5U4GB has the least amount of output voltage and the most sag. Additionally, there is a current lag in the tubes when they suddenly are “asked” to deliver lots of current when you strike a full E chord at high volume.  

Attack

Attack is the opposite of Sag which comes mainly from the amp, but Attack is also related to treble and sparkle. If you have a mellow guitar with warm, hot pickups its tone will have less attack than a clean guitar due to lack of sparkle and the fact that a bassy guitar tone will pr. definition lead to more sag in the amp. 

Headroom

The power of an amp and ability to play clean and loud without distortion or sag. An 85w Twin Reverb has more clean headroom than a 40W Pro Reverb. Whether an amp is able to play loud and clean depends on several things:

• Speaker efficiency and power rating. Some prefer the speaker to be the bottleneck while others want to maximize the volume and fullness.
• Tube types and configuration. EL34, EL84, 6V6, 6L6 all have different power rating. Using 1, 2 or 4 tubes will have different power ratings depending on numbers of tubes and how they work together (single tube Class A, dual tubes push/pull Class A/B etc.)
• Design of the power amp circuitry. One cannot always use power rating (wattage) to determine the clean headroom. Amps without negative feedback (like Vox amps, the Fender Vibro-King, ++) distort more than amps with negative feedback. Also, the bias design will determine amount of sag. Cathode bias (Fender Tweed era) has more sag than fixed bias (Blackface era).
• Preamp circuit design. If the preamp section is designed to distort on purpose, like Fender Bassman and Marshall amps with several tube gain stages in the preamp circuit, you will have less clean headroom even if the power amp section has lots of headroom. The phase inverter design will also affect clean headroom. The Princeton Reverb is known to have an inefficient phase inverter and will create a distorted signal already before it enters the power tubes. 

Hot and cold bias

A tube is basically an amplifier. Depending on the function in the guitar amp, its job is either to amplify the voltage or current, or both. All tubes require bias, meaning they must be provided certain voltages and current in order to operate. Preamp tubes have a circuitry around them of resistors and caps which provides the right bias voltages and currents. They do not require any user adjustment of bias. The power tubes do have bias adjustment possibilities and depending on preferences and tube type the bias can be adjusted cold, neutral or hot. Hot bias will lead to more distortion and earlier breakup while cold bias is the opposite. Hot bias therefore sounds best, huh? Be aware of that hot biasing will shorten tube life. I therefore recommend neutral/hot.  

Cranked  

Cranking an amp means turning up the volume beyond its sweet spot.  

Punchy vs Firm vs Tight vs Chunky 

Punch is to me used to describe how firm and tight bass notes an amp is able to deliver cleanly. When you pull and release the low E string SRV-style you will need punch from your amp to achieve a chunky tone (chunky = not distorted or flabby bass). Punch comes from several things: 

• Headroom and power.
• A powerful speaker, or several medium power speakers, with large magnets and solid cone constructions that can handle bass notes without farting out.
• Large power and output transformers with a low amount of sag. 

Spread 

An amp with good spread is at a large degree evenly heard in all positions in a room or a stage. The opposite is a directional amp. 10″ speakers are known to be directional while 12″ and 15″ have more spread. Closed cabinets have no spread backwards while open cabinets have decent spread in the front and back. Directional amps are more difficult to use on stage and requires micing and monitors. 

Scooped

A tone with reduced mids. If you study a signal in an oscilloscope the bass and treble are the dominating frequencies. A stratocaster is a typical example of a scooped guitar tone, particularly with weak/clean sounding pickups.  

Natural sounding

The word Natural means a flat frequency response.  

Sparkle

To me, sparkle is the upper treble frequencies of guitar and amp tone. The best example I can think of is the effect of the bright switch on Fender blackface/silverface amps. It will either let through or stop the sparkle of your tone. These are higher frequencies than the treble control will handle. Single coil guitars have more sparkle than humbuckers. A guitar’s neck wood and construction also play a role, same does pickups where hotter pickups with more coil winds will have stronger signal with less sparkle. One can use the guitar or amp tone controls to alter the treble, but if the speakers and guitar both are bright you may find it difficult to tame the sparkle. One example is a Fender Mustang with thin strings played through a clean Deluxe Reverb reissue loaded with a new, bright and efficient Jensen C12n speaker. It is very bright with tons of sparkle, sometimes tending towards “harsh” if you push the amp into distortion.  

Chimey

Much the same as sparkle, but not too much of it. A chimey tone is a nicely balanced tone with just enough sparkle. Chimey is often used in association with single coil pickups, relatively clean. 

Smooth vs edgy vs muddy

A smooth tone has a low amount of sparkle, meaning reduced high frequencies. People are different when it comes to smoothness.   

Some like edgy fuzz tones (think Fuzzface and other trebly fuzz pedals) while others prefer smoother overdrive tones (typically Tube Screamer) where the sparkle is tamed.  

A smooth tone can be muddy to others. A good example of muddy is playing chords with a warm neck pickup telecaster or a Les Paul humbucker through a moderately cranked Tweed Deluxe amp. It can be difficult to hear all nuances from the upper strings. Switching to the bridge pickup will give a much better balance and you’ll hear the upper strings as well.  

Liquid

Liquid means a chimey tone with fair amount of sag, obviously mostly associated with clean’ish tones. Liquid and Quacky might overlap a bit.  

Quacky

The best example of a quacky tone is the stratocaster’s in-between pickup positions, position 2 and 4. The two pickups, wither neck+mid or bridge+mid, are used in parallel and lots of frequencies are cancelled, particularly the upper mids. There is lots of sparkle and funky, firm bass in a quacky tone, and it is easy to get drowned on stage or get too muddy. If you master the difficult technique of pairing up with the right pedals, amp and speakers, you will experience Hendrix tone heaven and play Wind cries Mary dreamfully and beautifully. Be careful to not only play with a quacky sound. You should vary with single pickup positions to keep the audience interested. Dynamics and change of tone along the song are key requirements to all guitarists.  

Fullness

You cannot have fullness without strong bass and lower mids together with good spread, often related to larger amp and speaker cabinets and/or more speaker areal. A 2×12” cabinet sounds fuller than a 1×12”. A large 1×12” cabinet also sounds fuller than a small 1×12” cabinet, for example a Deluxe Reverb with 1×12” vs a Princeton Reverb where a replacement 12” speaker is squeezed into the small cabinet. A certain amount of power is also required to achieve fullness, otherwise the amp won’t be able to feed the large speakers with bass notes at medium/higher volumes. Bass requires a lot of energy and power. Treble does not. 

Vintage tone

Hah! The most hyped word in this business. Vintage tone is simply explained as the tone of a vintage amp in an original condition. To achieve a vintage tone, you first need a vintage-style amp with vintage-style speakers, preferably a real vintage amp with original speakers or very close replicas. You can of course achieve a vintage tone with modern amps as well as long as the amp is based on vintage specs. Vintage-style speakers are key to vintage tone. First of all, they are not powerful or very efficient. The original CTS, Jensen, Oxford, Utah, JBLs were typically 25-50w for 12″ speakers or 10-20w for 10″ speakers. Vintage style speakers are low-powered, natural sounding with medium/low efficiency. They do not have an impressive punch in the lower bass compared to typical modern speakers who have become very popular. Loud and punchy is always popular with beginners. Vintage speakers have strong treble, particularly the ceramic ones. Alnicos tend to be a bit smoother. Finally, a nice thing with low-powered speakers is their fingerspitzenefühl, aka touch-sensitivity. Given the light construction it requires very little energy/current to get the speaker vibrating.