« Why tube amps are still the first choice »
Users of tube amplifiers are aware of the advantages of analogue sound amplification and swear by the sound from the indestructible electron tube. But is there more to it than just myth, enthusiasm or nostalgia? In this article we want to talk about the technical advantages of these tubes, without hiding their disadvantages. Alongside technical facts and comparisons, we’ll also deal with the perception of human hearing and try to find out why tube amplifiers are still the first choice for many musicians and music enthusiasts.
How do tube amplifiers work?
When approaching this topic, it makes sense to first explain the basics of tube technology. Because a large part of the positive properties and advantages of tube amps are based on the technical facts. Let’s get to the overview with the question: How do tube amplifiers actually work?
Signal chain – the path from the input to the perceptible sound
Producing an audible, acoustic experience from an input signal – that’s the task of an amplifier. In the case of tube amplifiers, a wide variety of components work hand in hand. The input takes the signals of the source. With a guitar amplifier this is the signal from the guitar, with hi-fi equipment it’s the signal of the respective source medium, for example CD, mobile phone or MP3 player. This signal is now transmitted to the preamplifier.
It’s here that the preamp tubes come into the equation and raise the signal to a higher level. This is done by exciting a heating wire inside the electron tube to give off electrons. A signal amplification then occurs due to changed voltages in the interior of the electron tube. Especially with guitar amplifiers, the preamp tubes are also used to further influence the signal. This allows certain distortions and sound influences to be purposefully adjusted. In hi-fi applications, on the other hand, these influences are reduced as much as possible.
After the pre-amp, the signal finally reaches the power amp of the amplifier where the power amplifier tube raises it to a level which the connected speakers convert into a mechanical movement of the speaker diaphragm – the signal leaves the speakers and reaches the ears of the listener. The power amp is mainly responsible for the level. A distortion of the power amp is rather gentle in comparison.
Disadvantages of tube technology
Electron tubes sound great, no question about it. For us, too, there’s nothing in the world which can replace the sound of a good tube amplifier. But of course there are also reasons to be critical of this amplifier technology. So before we shed some light on the advantages of analogue amplifier technology for musicians and sound lovers, in the following part we’ll discuss the disadvantages of a tube amplifier.
High power consumption, high heat generation, high wear
The amplification by electron tube is based in the core on the glow of the cathode – without this property, the desired electron current wouldn’t occur. However, it is precisely this design-related property which is the core of the most common criticism of tube technology. The thermal stress a tube is exposed to accelerates the ageing process of the component and causes a change in the sound reproduction over time. The high heat generation also explains the high power consumption: up to 50% of the electrical power (depending on the type of circuit) is converted into unused heat. Finally, the signs of wear on the tubes cause the frequency and costs of maintenance to increase significantly compared to transistor technology.
Nonlinear frequency response and total harmonic distortion
While power consumption and wear tend to lead to increased effort during operation and maintenance, the typical criticisms of frequency response and total harmonic distortion are about sound influences: the frequency response of a tube amplifier is not linear; the amps have the property of accentuating high and low frequencies. The technical reason for this is the interaction of the speaker and amplifier, which together form a voltage divider.
The total harmonic distortion designated the amplifier’s tendency to distort the signal being boosted. While transistor amplifiers can have an extremely low total harmonic distortion, this is usually higher with all-tube amplifiers – so an unadulterated, “pure” reproduction of the signal is technically less possible using a tube – however, there’s still the factor of human hearing, which we’ll get onto in a moment.
Why use a tube amplifier? Tube amp advantages
No matter how outdated and old-fashioned tube technology may seem to some contemporaries, its advantages, even in comparison with the most modern technologies, cannot be denied. In the following, we’ll present tangible arguments which underline the advantages of tube technology.
Tube amp advantages: total harmonic distortion factor – Part 2
As we’ve already mentioned above, the total harmonic distortion is more noticeable with tube amps than it is with other amplifier technologies. Especially in the field of instrumental amplifiers (guitar amplifiers), however, this factor of tube sound is crucial to the popularity of these devices:
Unlike transistor amplifiers, tube amplifiers distort harmonically and don’t cut off the signal. Due to the way they work, harmonic overtones are added – so the amplifier distorts “in unison” with the actual signal, as it were.
The distortion achieved by this (the typical overdrive sound in guitar amps) is perceived by the human ear as much more harmonious and warmer – the typical creamy tube sound. Although high-fidelity enthusiasts are looking for a signal representation which is as true to the original as possible, tube amplifier models also have their advantages and justification in the high-fidelity world: it’s here that the warmth and naturalness of the sound comes into play – the amplifier is less analytical, but it offers the advantage of a higher level of musicality and allows for more authentic sound experiences.
Tube amp advantages: simpler circuitry, simpler repair, flexibility in sound adjustment
Tube amps are often criticised for their more vulnerable technology. However, the simple switching and maintenance of the amps also has one significant advantage: preamp tubes can usually be replaced through a simple “plug & play” – so get the old tube out, put the new one in and off you go. However, power amplifier tubes have to be matched with each other and usually a bias correction has to be performed. If in doubt, please contact TAD (email@example.com). With the best spare parts for amplifiers, even small repairs are easy to perform on your own.
Also, the sound of the amp can be adjusted with a simple tube replacement of the pre- or power-amp tube. In particular, the use of different preamp and power amp tubes can significantly influence the sound as well as the area of application of a guitar amp, offering a significant advantage. From this point of view, a tube amp is therefore much more versatile and easier to handle than a transistor amplifier, where an internal defect is often associated with the amp giving up the ghost.
Retro charm, tube sound and myth
Although these are not technical characteristics, it’s still an advantage which plays a major role in the popularity of tube technology: the charm tube amplifiers convey is unabated. Especially these days, when music and media are omnipresent consumer goods, the focus on deliberately “listening to music” has often been lost. By actively listening using analogue technology which we can see working, we can recover a part of this:
The charm of the imperfect, handmade sound and the authentic sound experience still comes exclusively from tube amplifiers. The pre-heating, the setting of the amp and the melodic distortions and overtones make the enjoyment of music much more palpable, conscious and tangible.
Why tube amps are still the first choice – conclusion
From a technical point of view, there are advantages and disadvantages which can be mentioned for tubes. In the end, when it comes to enjoying music, the most important thing is personal taste and listening sensation. That’s why we recommend this test to every open-minded critic of tube technology: a cosy armchair, a glass of your favourite drink and listening to a good album using a tube amplifier – this sound experience looks very persuasive. Guitarists, on the other hand, let the tube pre-heat and play the guitar amplifier without any additional effects after the guitar – a little overdrive from the preamp tubes and things are already looking up!
Header Image © Boris Bulychev – stock.adobe.com
Tube amp close-up: © Mladenov – stock.adobe.com
Tubes in operation: © otent – stock.adobe.com
Man with headphones: © cherryandbees – stock.adobe.com
Electric guitar player: © ValentinValkov – stock.adobe.com
Many loudspeakers of a hi-fi system: © Konstantin Gushcha – stock.adobe.com