Buying guide for best preamplifiers
Are you thinking of picking up a preamplifier for your audio system? The first time you hear it powered up, we think you’ll be glad you did.
As the name implies, a preamplifier is a device that you place in your audio chain prior to the amplifier. It is here that the preamplifier helps shape and define the audio signal. It can also amplify a weak signal.
Though the purpose of a preamplifier may seem simple, the end result can make a strong difference in the overall audio quality of your sound output. But preamps aren’t cheap, so you certainly want to do your homework before buying one.
Key considerations
Preamplifier circuit design
Preamplifiers are available in three configurations based on circuit design. There are some fundamental differences between the three that may impact your choice.
Tube preamplifiers: Tube preamplifiers use vacuum, or thermionic, tubes to create their unique sound. This is an old-school option that users love for its vintage color: crisp highs, a deeper bass, and overall warmth to the sound. Some tube amplifiers feature completely enclosed tubes; others have tubes extending from the top of the chassis. In addition to costing more than other preamplifier options, tube amplifiers produce more heat than other circuit types.
Solid-state preamplifiers: Transistors replace tubes in solid state preamplifiers. These preamplifiers feature fast signal processing and are usually less expensive and more efficient than tube preamplifiers.
Digital preamplifiers: Digital preamplifiers convert audio signal to digital signal, which is then sent to something like a DAW (digital audio workstation) for processing. Digital preamplifiers are similar to digital interfaces.
Multi-source vs. source-specific
While some preamplifiers work with multiple sources, others work best with a specific type of source, such as a phonograph. Other sources can include a computer, instrument, microphone, iPod, TV, Echo Dot, or another audio device.
If you plan to put a preamplifier to a specific use, check the product specs carefully to verify that the preamplifier will meet your needs.
Power source
Preamplifiers are typically powered via a 12V DC adapter, but some also run on battery power. This is a big plus when outlets are scarce. Be sure that any preamplifier you purchase ships with the adapter.
The majority of preamplifiers ship pre-assembled, but some require assembly. While this is typically not that involved, people who are adverse to assembling such devices should take note.
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Features
Chassis
The outer casing of a preamplifier is usually made of plastic or metal. Metal is more durable, physically protecting the inner circuitry of the preamplifier better than plastic. Metal also has the advantage of offering better shielding from electromagnetic interference and vibrations.
Inputs
Preamplifier inputs allow you to plug sources such as a computer or turntable into the preamplifier. RCA-type inputs are standard, but some preamplifiers offer other input options, such as USB or Bluetooth. Some preamplifiers feature source switching so you can easily switch between audio sources.
Outputs
Outputs allow you to send the signal from the preamplifier to some form of amplifier. While RCA-type outputs are again standard, some preamplifiers offer multiple output options, such as a 3.5mm stereo plug, so you can send the signal to a variety of sources.
Controls
Controls vary from one preamplifier to the next, but some common ones include the following.
Volume and gain: These controls allow you to modify how loud a signal is when leaving the outputs (volume) or entering the preamplifier through the inputs (gain).
Tone: This control affects how much treble or bass is in the signal.
Balance: In stereo preamplifiers, the balance control gives you fine control over how much signal reaches each speaker.
As mentioned, some preamplifiers include a control for switching between sources.
High-pass filter
Also known as a low-cut filter, a high-pass filter is available in some preamplifiers. It enhances the signal by allowing high frequencies through while filtering out low frequencies. This is particularly helpful in removing bass in systems with speakers that are less robust.
Indicator lights
Some preamplifiers feature indicator lights that alert you to a variety of conditions, such as whether the preamplifier is powered up, whether a signal is present, and whether the signal is clipping.
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One benefit of a solid-state preamplifier over a tube-based one: solid-state preamplifiers tend to have fewer maintenance issues, particularly as they become older.
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Preamplifier prices
Inexpensive: For $20 to $45, you will find simple preamplifiers for use with a turntable or headphones. These tend to have simple RCA inputs and outputs and minimal controls.
Mid-range: Between $45 and $70, you will find more input/output options along with more controls so you can fine-tune your signal. These preamplifiers can typically be used with a variety of sources and are best for home theater or audio fans who want to improve their overall audio quality. Some simpler tube preamplifiers are also available in this price range.
Expensive: Anything over $70 is a more serious preamplifier. Geared toward audiophiles and music professionals, preamplifiers in this range offer full-featured control of your audio signal with a variety of input types and source switching to handle all of your audio sources in one hub-type component. Tube preamplifiers are common in this price range, as are a variety of control options. If you’re searching for the best signal quality with no hum or background noise, this is the price range for you.
While rare, some preamplifiers are hybrids that allow you to easily switch between a tube and solid state design.
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Tips
- If you’re using your preamplifier with a turntable, check for a “GND” post on the preamplifier. If it has one, run your turntable ground wire to it. Doing so can prevent turntable hum and other noises from corrupting the signal.
- Be aware that although gold-plated connectors sound fancy, they are mainly for show. Gold is actually a poorer conductor of electricity than copper. However, it will not tarnish like copper. If shiny connectors are important to you, this is a noteworthy feature.
- Make sure the phono preamplifier you buy is designed to work with your specific type of cartridge. There are two primary types of phono cartridges: moving magnet (MM) and moving coil (MC).
- Make sure the preamplifier you select would work with your musical instrument. For example, if you play electric guitar, you’ll want a preamplifier that is geared toward the electric guitar.
- If you want the preamplifier to draw no power when not in use, unplug it or turn it on and off via a power strip. Preamplifiers typically do not feature an on/off switch.
- If you’re experiencing hum or other noise problems, try replacing the cables before tackling more involved troubleshooting options. One common, and easily fixed, source of unwanted noise in a preamplifier is low-quality cables.
FAQ
Q. If I already have a mixer or audio interface, do I really need a preamplifier?
A. While mixers and audio interfaces often incorporate preamplifier elements within them, the quality of such preamplifiers will be poor compared to what you would get with a dedicated external preamplifier. To coax the best possible sound quality, consider picking up a dedicated preamplifier.
Q. What is audio clipping?
A. Clipping refers to an overdriven signal that can result in a distorted wavelength, leading to poor signal quality. You can usually fix this in a preamplifier by adjusting the gain down. Some preamplifiers include an LED light that alerts you to clipping so you’ll automatically know when to adjust the gain.
Q. What is an analog input capacitance switch, and how do I use it?
A. Analog input capacitance switches are included with some preamps, particularly those designed for use with turntables. This switch allows you to change the capacitance, usually from 100pF to 200pF, to better work with your turntable.
To use this switch correctly, check your turntable cartridge specifications and set the switch to the proper capacitance. Some users won’t detect a difference between the two, but it can lead to a cleaner signal if you have the switch aligned to your cartridge specifications.
