The Dos and Don'ts of Buying a Preamp

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The Dos and Don'ts of Buying a Preamp

There are few components that resemble musical instruments quite as closely as preamps do. This little-known and oft misunderstood device is generally used purely out of necessity by turntable fans needing a signal between their cartridge and power amplifier, but this is too humble a task for this versatile gadget. When preamps are used to their full capacity, they are capable of fulfilling fussy audiophiles' dreams by allowing the fine-tuning of the tonal character, output impedance and gain of sound signals. Those who want the portability and ease of use of a solid state power amplifier without the cool tone can achieve a perfect balance by altering the settings on their preamps. Those on a quest for the distortion-free audio that seldom exists outside of legends have a better chance of success when they add a preamp to their sound systems.

Don't Confuse Active and Passive Preamps

Active preamps need a power source to operate with, while passive ones merely arrange or dissolve energy. The latter group is incapable of adding power to signals unless they have built in transformers and inductors. There are some imperative differences between these two categories that have a clearly definable impact on sound quality. Passive preamps are often attributed with powers they don't have. Some preamps have a switch that transforms them from active to passive components. Some automatically act as passive preamps when their batteries die.

Active

Passive

Powered by batteries or an electricity source, which allows them to amplify sound signals.

Power is taken directly from the frequency range, which renders them incapable of adding to the overall power of the system's signal.

Systems with particularly long cables need an active preamp to decrease the amount of frequency lost.

These components need to be placed near to the power amp to cut cable length and avoid the muting of treble.

Output impedance can be reduced and interference caused by other components can be isolated.

The ability to retain interference is a preference for some, who enjoy the positive distortion and warmth of this effect.

Able to power all frequencies accurately so that bass, treble, and middle ranges receive the restrained power they need.

The ability to act on individual frequencies is limited. Instead, these boost wider sets of frequencies with less accuracy.

Decide Between Audio Accuracy and Warmth

Preamps can be divided into transparent and coloured components. Rather than referring to visual aesthetics, these two labels define their influences on audio quality.

Coloured

Transparent

The audio is coloured by an organic, timbral tonal quality.

These preamps deliver audio that is accurate and untouched by tonal influences.

Capable of turning a thin audio track into a full-bodied sound. Various sonic signatures can be applied to audio to achieve ranged effects.

Purists prefer the unadulterated authenticity of true to life audio that is left untouched by too wide an array of inbuilt components.

Transformers add colour to the tone, as does tube-based circuitry.

Transformers need to be absent if true transparency is to be achieved. Transformerless designs are most functional in solid state preamps.

Understand Circuitry's Influence on Audio Quality

The ongoing debate about the superiority of tube or solid state power amps is equally applicable to preamps. In recent years, manufacturers have begun to release hybrids in an attempt to gain the advantages of both circuitry types. The overall goal of this particular element is to achieve power efficiency that prevents overheating and to eliminate clipping.

Tube

Solid State

Tube and solid state hybrids

Modeling

Valves are used to achieve gain, which allows them to power deep, high and mid-range frequencies well.

Gain control is more power efficient, reducing overheating and thus omitting some forms of distortion. Solid state preamps can cope with a higher gain, which contributes to the authentic delivery of sound signals, even at high temperatures.

Input and output stages are driven individually by solid state and tube components respectively.

Emulates a range of sonic characteristics according to processing. These preamps can mimic the tones produced by tube and solid state components, or any sound signature in between.

Sound is coloured by a warm tonal character. A higher level of distortion adds to the body of the sound. Filters are used to restrain distortion, preventing unwanted noise.

Sound accuracy is high, generating a transparent sound that is unhindered by external influences.

Tube driven output gain control achieves a saturated, rich sound, while the clarity that applies to solid state preamps is achieved through the quick response time.

Solid state circuits are merged with digitally generated sound qualities.

The warmth and harmonic handling that tube preamps achieve make them a popular choice for acoustic and vocal recording. Guitarists and turntable fans often prefer them for their organic sound.

Solid state preamps are expensive which, with their transparency, makes them a preference among professional musicians and purists.

These affordable preamps are flexible enough for amateur producers and musicians who haven't defined their audio preferences yet.

Highly applicable to the needs of professional recording studios.

Don't Overdo the Tonal Warmth of Preamps

Turntable fans, vocalists, acoustic guitarists, and traditionalists tend to choose preamps according to the warmth they achieve. In many cases, analogue sound can become too warm to achieve clarity. Overly smooth, thick sounds may damage the fidelity of high frequencies, rendering the system's tweeters moot. Warmth comes at a price, and there is a fine line between positive distortion and noise. Preamps capable of organic sound have a penchant for producing more heat, which ultimately becomes undesirable noise. Sometimes, warmth and clarity can be merged through the simple addition of a comprehensive channel strip. This component allows listeners to force their preamps to process frequencies differently so that they can be adapted to the genre of music being played. Preamps that can process signals using additional circuits are called channel strips.

Channel strip features

Functions

Signal processing tasks are merged into a single unit.

A reduction in separate inbuilt components automatically reduces negative distortion.

Adds an additional sound processing phase with compression.

Audio is degraded by every addition to processing but slight compression can add a desirable tone to certain recordings.

Individual components control multiple channels separately.

This allows listeners to fine tune separate signals for every instrument or musical genre.

Processors and preamps can use their own separate solid state or tube technology.

Experimenting with the effects of merging tube and solid state mechanics helps musicians and recording professionals to develop their own signature sound.

Focus on Noise Cancellation

A preamp should be honed specifically to erase negative distortion. Fans of warm analogue tones will seek out a certain degree of distortion, but there is a bold line separating desirable distortion, audible noise and inaudible noise. It is unnecessary to spend vast amounts on trying to eliminate noise levels that are so negligible that they cannot be detected by the human ear. Those seeking a symphony experience usually want to omit all audible distortion to attain a clearly channelled, crisp sound. Analogue fans who want a traditional timbral tone will choose colour preamps with low level distortion. The highest quality preamps use balanced inputs and outputs to cancel out undesirable distortion.

Balanced Input and Output Cables

Unbalanced Input and Output Cables

Sound lacks noise when short cables are used.

Amplification stages are divided into left and right using a phase splitter.

Most efficient when used with a preamp that has balanced output.

This system needs a differential amp in addition to the power amp. Extra components generate more noise.

Best for converting digital sound signals into analogue formats.

Unbalanced preamps are most compatible with unbalanced connections.

Conclusion

The pursuit of perfect sound can become a costly quest for obsessive audiophiles. Preamps are an affordable way to resolve the problem of distortion. They have the counter-intuitive ability to make audio seem to be louder without creating undesirable distortion. While the additional phase this component adds to the travels of sound signals can lead to unwanted compression, for listeners who value the traditional warmth of old fashioned analogue, preamps are a necessity. Musicians and recording artists are seldom satisfied without a series of their own preamps. For those who are constructing their own home audio system, these devices can adapt to listeners who want their audio to reach their ears untouched at high volumes without distortion.

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