What are guitar preamps and how to choose them?

In order to amplify or record on a medium the relatively low sound of an acoustic guitar, as well as to sound an almost silent electric guitar itself, you need to connect them to a guitar amplifier. But the latter needs one more important link to obtain a high-quality sound - a preamplifier, or a preamp. In modern factory amplifiers, the preamp is already built into a single case with a block of amplifying and reproducing equipment. However, this is not always convenient. This and other features of guitar preamplifiers, as well as the choice of the best of them, will be discussed further in the article.

If we talk about the functions that are assigned to the guitar preamplifier, then we can list the following number of its main tasks:

• receiving electrical signals from a musical instrument;
• processing of received signals in order to improve their quality;
• amplification of signals to the line level;
• transmission of processed signals to the power amplifier unit.

To put it simply, the preamp works, it prepares the incoming signal from the guitar or microphone pickups for its further processing and transmission further to the power amplifier and speakers. By improving the quality of signals we mean the fact that it is in the preamplifier that the sound acquires a unique timbre and is enriched with some effects, for example: “distortion”, “enhancer” and others. A quality preamp is the foundation of a successful public performance and sound quality recording. The guitarist cannot do without it in cases where it is impossible to take the entire guitar amplifier with him.

And the device itself is an electrical or semiconductor circuit with a hardware set (lamps, transistors, resistors and capacitors, interconnected in a certain way, ensuring the correct operation of the preamp). The preamplifier is connected schematically between the guitar and the main amplifier, and the speaker is located at the very end - on the output channel of the guitar power amplifier. The preamp amplifies the weak signal coming from the guitar pickups by increasing the voltage. In this case, the current strength changes insignificantly. The current increases in the main amplifier, and the voltage also rises there again.

It is also worth noting that the preamp itself, connected to a musical instrument, without a power amplifier does not give any external sound, therefore it is suitable only for recording, and not for a concert stage. But its important influence on the original sound is an undeniable fact. Often the preamps are already built into the body of the guitar, so it will be enough to purchase only an amplifier (the option of a power amplifier without a preamp will cost less than a complete sound reproducing kit).

Preamplifiers for acoustic and electric guitars are classified into two main types: tube and solid state. Let's give them a brief description.

• Lamp. Immediately we can say that tube preamps are valued quite highly, since lamps are those parts of this device that add depth, warmth, and musical harmonics to the sound. They also say that the sound becomes "bold" due to tube transformations of signals, that is, the density and airiness of the sound are fully felt. In addition, tube devices have natural compression, which is very pleasant to the ear.

• Transistor. In contrast to their tube counterparts, these preamplifiers are considered "transparent", that is, they do little to color sounds with harmonics and effects. They work without generating heat, economical and neat. However, such devices do not need distortion, since transistors, although they work with high signal amplification, do not allow distortion.

In addition to "pure" transistor or tube devices for pre-amplifying the sound of guitars, there are also hybrid preamps, which include components of both tube circuits and transistor ones. For example, there are options for which the input part is assembled on transistors, and the output is regulated by the lamps (Summit Audio 2BA-221 preamp). In this case, the input signal from the pickups or microphone is processed faster, cleared of noise better, and at the output, due to the lamps, it is saturated with effects and warmth. It turns out a gain in almost everything.

Choosing a preamplifier for his guitar, a professional musician playing an acoustic instrument will first of all think about the individuality of its sound, that is, he needs: a beautiful and natural timbre of the instrument, sound density and good high frequencies. In this case, he will most likely need to choose a hybrid model. It will be able to clean and amplify the input signal, preserve the high frequencies and color the sound at the output. A transistor version is possible if the guitar lacks speed and treble.

If the guitar has a subtle sound that does not hurt to add thickness and density, then the tube preamp is the best choice. Conversely, with good low and medium frequencies, it will be better to purchase a transistor version, so as not to overdo it with too thick sound in the high frequencies, adopting a tube preamp model.

For beginners, either the transistor model or the hybrid can be recommended. In any case, they are a winning option for an inexperienced guitarist: less money is required, and the sound is clean, with a good timbre.

But each guitarist has his own vision of sound, therefore, through experiments and mandatory verification of the operation of the purchased model of a guitar preamp complete with his guitar, it is necessary to find the desired option.