Some people say the preamp is the “heart of your stereo system,” because it is the central point where all your music sources come together, and it determines which source you listen to. That’s true, but it doesn’t explain why the preamp is the heart of your stereo. Let’s cover the most basic part of this question: what is a preamp?
The Official Version: A preamp, or a preamplifier, is a part of a chain of devices that produce a music signal and has several possible functions, which at least include the ability to “turn down the volume” of the music signal. This blog will focus on home stereo preamps, but there are other types of preamps, including microphone preamps used in recording studios and professional concert settings, and guitar and bass preamps.
The Easy Version: A preamp is basically a box that lets you control the volume of music, and *usually* lets you do a few other things:
– A preamp usually lets you feed several sources of music into it, and then lets you select which music source you want to listen to. CD player, turntable, etc.
– A preamp allows you to adjust the volume all the way down to silence. If you have a “passive” preamp, that’s all you can do, volume-wise. An “active” preamp also does this, and in addition lets you “turn the volume up” even louder than the music source’s output, which may be necessary if your music source (DAC, phono preamp, etc) doesn’t have enough gain to properly drive your power amp. This means that an active preamp is also a full-fledged “amplifier,” and has circuitry inside that boosts the music signal using one or more “gain stages”.
– An *active* preamp (such as a Backert Labs) usually manages the impedance of your music sources, so that the impedance of the signal being sent to your power amplifier is relatively constant and is kept relatively low so that it does not impair sound quality. A passive preamp is unable to manage impedance, and will output different levels of impedance depending on where the volume control is set, potentially making music sound different at different volumes. A passive preamp will output higher and higher impedance as the volume is turned up, and at some point will be higher than the power amp is suited to accept, resulting in sound that is bass-shy and generally weak. This “impedance mismatch” is why owners of passive preamps are often delighted when they switch to an active preamp.
OK I get the theory, but what kind of physical thing are we talking about? Music lovers are often introduced to the idea of a preamp after listening to music through a receiver, or “integrated amplifier”. Typically, they might wonder how to improve sound quality, at which point they learn that their receiver or integrated amp is really just a combination of a *preamp* and a *power amp* in one box. Many critical listeners believe that buying separate components that focus on the preamp task and the power amplifier task exclusively improves sound quality. So, the next step is to buy separates, i.e., a preamp and a power amp. A preamp is usually smaller, somewhere near the size of a CD player, while a power amp is often larger, perhaps the size of 2 CD players together. However, some preamps are massive, filling up 3 and even 4 separate chassis, and some power amps are the size of a cigar box.
The amplification that an active preamp provides can be provided by solid-state devices (usually transistors) or can be provided by tubes, as is the case with Backert Labs preamps.
Why the preamp is critical: A preamp takes the music at its very source and provides the first level of amplification the music will see as it makes its way to your speakers. If that first stage of amplification isn’t perfect, even the greatest power amp on Earth will never be able to “put it back together” and make it sound great.
What kind of “damage” can a merely average preamp do to your music? Well it can introduce phase shift or impedance problems. It can “fog up” the sound quality, or make it grey, lifeless, and sterile. And many preamps will subtly impair the timing of your music, so that what you hear ends up sounding slow, or simply, “like a stereo”.
Therefore a good preamp is absolutely critical to your musical enjoyment. This is why we believe that the preamp-like functions in DACs and CD players are very often not good enough. And it’s why we at Backert Labs make nothing except preamplifiers. It’s why we are the preamp specialists.
