When talking about valve amps we instantly think about their characteristic tone, sweet, distorted, and glassy sound which resembles those bands from the 60s and 70s.
The power tubes and preamp section are the ones in charge of the magic.
Due to those features, tube amps are extremely wanted by musicians but how the tone is shaped? Which components influence the outcome?
Do power tubes or the preamp stage directly affect the tone?
Power tubes do intensive work in valve amps, they are the ones in charge of not only amplifying the signal but also modeling the tone. There are several diverse tubes and they vary their performance and tone from one model to the other.
Although this could sound confusing and even overwhelming, we are here to clarify every needed aspect regarding this issue.
Through this article, I will explain why power tubes are that important, how they work, the different models, and more, in the end, you will become an expert in this field.
Why are power tubes that important?
When we talk about power tubes we refer to the big glass bottles in the back part of your amp.
Although they are commonly known by that term, they are in fact output tubes which could be a more accurate way of naming them due to these tubes creating your amp’s output.
What is more, the term “power” may cause confusion with rectifier tubes, which lie on the power stage of the amp.
To recognize these two kinds of tubes, you have to pay attention to the size, power tubes are bigger than rectifiers plus in valve amps, you will usually find two or more tubes that look the same, those would be output tubes whereas the different one would be the rectifier tube.
Power tubes play an important role in valve amps because they are the amplifier within your amp, which means that they are in charge of increasing the output, they amplify and drive your signal.
However, they are not just involved in producing the proper output, they also take part in shaping the tone.
Do power tubes define the tone of an amp?
Although when talking about the sound it is always subjective, a lot of people prefer tube amps.
That may be because, from a technical point of view, tube amps are superior.
Tube amps are not only amplifiers, they also provide natural distortion which takes an important place when modeling the tone.
This presented distortion is not the same as the one found in distortion pedals, we are talking about an effect that enriches the tone, which makes it better.
This kind of distortion is usually called harmonic and becomes your tone warmer and well-rounded, without it a guitar could sound thin or weak.
What is even more, these amplifiers are less prone to clip, the more input the more distortion.
Because of all mentioned, valve amps sound warmer and have a better overall tone. That’s what makes them so desirable.
Most popular power tube types and their sound
As previously discussed, we can think of power tubes as the soul of the amp, they are in charge of amplifying and providing the proper output plus shaping the tone but are they all the same? Can we get new results using different power tubes?
Power tubes are not equal, they vary in shape, size, and tone, by employing distinct valves you will have a diverse outcome.
There are many kinds of power tubes, so let’s take a look at them and see the results we can achieve.
These power valves were one of the first used in amp construction, they were really common and easy to get back in the 30s.
Focusing on the tone, 6L6s do not have a strongly distorted sound, they provide a clearer clean tone instead.
6L6 tubes were an American design and due to their availability there, a lot of valve amp builders used them in their crafting, perhaps that was the reason why Leo Fender employed them.
Compared to EL34, 6L6 provides a less strong midrange and the overall tone is not so stony but way smoother.
When Marshall was making their first valve amps 6L6s were not available so the company employed EL34 tubes to build the equipment. Contrary to 6L6, EL34 was a European design that’s why was used not only by Marshall but also by many other brands such as Hiwatt.
Through these power tubes, the British tone was built up and as opposed to their American competitor, EL34 provides more powerful mids and a muddier, dirtier tone. That does not mean that these tubes produce a greater amount of distortion, they just give a more aggressive outcome.
Musicians usually refer to this sort of valve as 6L6’s little brother, and it was commonly used as well. Fender made use of them in their classic amps (Deluxe Reverb and Princeton), gears typically used by American groups in the 50s and 60s.
Just as EL84, 6L6 is a smaller tube that works for tinier amps, but they don’t sound alike at all. Whereas EL84 barks when cranked up, 6L6 roars plus provides a wonderful lead tone, having an amazing sparkle in the treble tones and a consistent low end without mentioning the chime in the harmonic tones.
If 6v6 is 6L6’s little brother, EL84 would be EL34’s younger brother. These power tubes could be found in VOX equipment plus they were used by a group of guys you might know, The Beatles.
As mentioned before, the EL84 is a smaller tube that was designed to work without a drive tube, which provides more gain than other gears. That means that amps with EL84 power tubes could amplify the signal way easier than other valves.
Regarding the sound, they have a defined presence in the midrange. As they need lower power to work, they provide a dirty output even when you use a clean tone.
Although these tubes provide a similar sound to the 6L6, they have their own character, they are able to produce a bit stronger mid-range plus they offer a good amount of headroom resulting in more clarity when playing. KT66s were employed in the construction of some Marshall Plexis during the mid-60s.
6550 power tubes are the standard in the Marshall AFD100, it was created in 1995 and is commonly used to add a bit more power than both 6L6 and EL34. Concerning the tone, it is quite the same as the 6L6, it provides a clean tone with a little distortion.
As it gives a gritty sound in the midrange, sometimes it could be too choppy for clean tones and pretty cloudy for dirty tones. However, lead lines can reach fluid and smooth sounds.
Last but not least, we have the KT88 which has similarities to a 6550: the KT88 has a good amount of clean headroom plus a distinguishable low end and a strong presence in high frequencies. These power tubes do not provide a great punch in the mid frequencies so where the EL34 barks in the mids, the KT88 does not.
What other kinds of tubes are on an amp?
All-tube amps come with preamp and power tubes, their construction and function are quite different but both of them are involved in shaping and amplifying the guitar’s tone.
We have already talked about power tubes but what about preamp tubes? Let me explain to you.
Preamp tubes are generally smaller than power tubes, they are involved in shaping the overall tone of your guitar sound.
They do that by taking the signal from the guitar’s pickups and pre-amplifying it to be sent to the power amp section later.
These tubes are the base of the sound that you want to listen to as the output because they are the shapers of the amp’s tone.
The interesting thing about this sort of valve is that by overdriving it you can get rich harmonics, distortion, and consistent sustain but that isn’t all, you can also get bright clean tones.
Guitar amps also have another type of tube, they are called rectifier tubes and their work is to convert the voltage from the power source, which is AC, to the DC needed in the internal processes of the amp’s circuits.
When solid-state diode rectifiers appeared in the 1950s, tube rectifiers were left aside and replaced by brand-new equipment.
However, in 1991 MESA Boogie launched an amp with selectable rectification, with MESA Dual Rectifier Amplifier you can choose whether to use tubes or diodes which offer more and new tonal options.
If you are interested in learning more regarding this specific amp we have an article that fully covers its relevant features compared to MESA Triple Rectifier, I will leave you the link to it below.
Do tube amps sound good at low volumes?
Contrary to what most players believe, tube amps are completely usable at low volumes, they sound incredible when cranked up but it is not true that they sound horrible when are quiet.
What actually happens is that tube amps are intended to work at high volumes, most of them reach their sweetest sound point when pushed to the limit.
Although this equipment is completely playable at low volumes, the saturated overdriven, spicy tone is achieved only when you crank the master volume; a softer amp volume could be great for practicing at home but you won’t get the whole experience, you won’t know what tube gears are capable of doing.
If you still feel curious about this issue, I will leave you a link to one of our articles which explains everything regarding tube amps at low volumes.
What makes tube amps sound better when cranked?
When you turn up the volume of your amp, you will notice that everything sounds better, notes are louder so they are more noticeable and you can listen better to the high frequencies.
All amps sound better at higher volumes, tube amps are not the exception because, as previously explained, power tubes produce naturally distorted sounds by turning the master volume up.
When pushing the volume in the power amp section to the maximum, the tubes overload and you will get those sweet and desirable harmonics that the overdriven signal provides.
As they are designed to take profit from this feature, they sound amazing if you crank them up, you will get killer blues tones plus the distortion will be way better, richer, more dynamic, punchier, and less compressed.
Are all kinds of power tubes the same at low volumes?
We already know that valve amps do not offer that distorted tone when playing at low volumes, so the diverse power tubes’ sound wouldn’t be way different, they have their own outcome but when they aren’t cranked their influence is pretty small.
Nevertheless, the magic appears at higher volumes, that is when you can really see their particular character, although they share a certain degree of features, at louder volumes the performance varies.
Is there any way of getting a saturated power tube sound at low volumes?
The easiest way to get the saturated overdriven sound by playing at low volumes is getting a low wattage tube amp. In that way, you will be able to crank it without playing at high volumes.
Although is the simpler option and the most straightforward, you have other alternatives, for instance, you can go for an attenuator.
Basically, what an attenuator does is drive your tube amp harder, we all know that the harder tubes amp are driven, the better they sound but how this device works?
Attenuators are located in the middle between the output and the speaker, they use a coil to reduce the wattage and convert the exceding wattage into heat.
By doing that, you will be able to crank the amp more easily because the amount of wattage that is reduced is sent to the speakers, which allows reproducing the tone of a pushed amp at a reduced volume.
Hello there, my name is Ramiro and I’ve been playing guitar for almost 20 years. I’m obsessed with everything gear-related and I thought it might be worth sharing it. From guitars, pedals, amps, and synths to studio gear and production tips, I hope you find what I post here useful, and I’ll try my best to keep it entertaining also.