Recording the voice (03) The preamplifier(Letto 94 volte)

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The preamplifier

Besides the microphone, the preamplifier is another fundamental element in the recording chain.

Choosing the preamp

We have already considered above what concerns the choice of a preamp (or microphone) of this type. valve compared to one at the solid state.

A high-quality preamplifier, while not having the same impact as a microphone, is also an important element in determining the sound quality of a vocal recording, in terms of:

impedance matching

Each microphone requires a specific load impedance from the preamp, these values can be found in the technical data sheet of the microphone and the preamp itself; a perfect match ensures that the microphone's performance is very similar to that intended by the designer; deviating from the right values changes the sound, creating the preponderance or lack of the mid register; to manage the versatility of the match, some preamps are equipped with a load impedance selector.

alchemical coupling

Some microphone pairings can be particularly successful; unfortunately, there are no rules in this regard, but you need to experiment; as an example, I could mention the pairing between the Neumann U87 and the UAD tube preamp, or between the same microphone and Neve preamps, or even this last preamp with the Rode K2 tube microphone; it's up to you to try these and other solutions.

tonal and dynamic coherence

A good preamplifier should guarantee a constant tonal and dynamic performance at various gain levels; lower-level preamplifiers, on the other hand, offer a relatively narrow quality range, in which they can express the best of their characteristics with good consistency of performance.

background noise

By now all modern preamplifiers, except for some very cheap models or some valve-based ones, guarantee an excellent signal/noise ratio, excellent for using high gain levels without creating too high an incidence of background noise.

transient speed

A fast and precise transient response is an element that distinguishes a high-end preamplifier from a more modest one; in particular, if a transient peak rise were very large and fast (especially if localized at low frequencies), it would put a strain on the preamplifier; fortunately, the voice is not endowed with extremely fast transients, nor with particularly low frequencies; it follows that this characteristic is not essential for a preamplifier intended for vocal use; however, a good transient response is necessary even in this case.

fidelity

The fidelity of a preamp means its ability to amplify the signal coming from the microphone without substantially modifying its tonal and dynamic balance and without introducing any harmonic distortion.

transparency

There are actually preamplifiers defined transparent which are distinguished from other defined colorful, as well as all the intermediate options; what's the difference? Here it is:

• A particularly transparent preamplifier will tend to express maximum fidelity up to values very close to clipping; harmonic saturation will tend to express itself only in the last few dB close to clipping – it is particularly suitable for acoustic sources in the context of “purist” musical genres, such as classical music and in any case where the need for extreme fidelity and cleanliness is felt; furthermore, it is always preferable for crystalline sources such as cymbals, the triangle, high-range wind instruments with a sound close to sinusoidal (such as the flute and the piccolo).
• A particularly colored preamplifier will tend to express a little harmonic saturation even with gain values relatively far from those of clipping; furthermore, it will tend to give the sound a slightly different color from that generated by the microphone, both tonally and dynamically; this type of preamplifier is often preferred in modern and aggressive genres such as rock, pop, funk, dance, especially when it comes to drums, bass, electric guitars and synthesizers.

for the voice, the preamp should be chosen according to the characteristics and character of the voice and the musical genre, taking into account the fact that, at medium gain levels, even a colored preamp is almost free from harmonic saturation.

harmonious richness

by harmonic richness of a preamp we mean:

1. the ability to retain the original sound sent by the microphone (in this case better defined by the concept of "fidelity")
2. the ability to create new quality harmonics by means of harmonic saturation

harmonic saturation

This refers to the ability of a preamplifier to generate, at high gain values (typically in the high headroom range), a good quality harmonic saturation, which can determine a timbre enrichment rather than an unpleasant distortion; saturation is not always welcome, especially in purist genres such as classical music and others in which an extreme clarity of the audio program is required; in other musical genres, however, it can often be very pleasant, capable as it is of warming and enriching an otherwise thin and cold sound.

clipping resistance

a high quality preamplifier, finally, will be able to deliver a very powerful signal before entering clipping, making the latter assume values equal to or greater than 22 dB (up to 26 dB, in certain cases) above the 0 dB reference.

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Two examples of preamplifiers: above, a modern and affordable model from Behringer; below, the stereo preamp version from Neve, a legendary brand that produces top-quality preamps.