What is a phono preamp and how do you use one?
A phono preamp is a device that acts as a translator between your turntable and your speakers. The signal that comes out of the cartridge on any turntable is about 1000x lower than the signal that you would get from a CD player or streaming device.
Since this signal is so low, you need something to boost it so that you can hear it through your speakers. A phono preamp, or phono stage, amplifies the signal from your turntable to a level that allows you to connect it to your stereo system, in much the same way that you would connect with any other audio source.
Features to consider before buying
There are several key features that you need to take into account when you are looking for a great phono preamp. In this section, we will cover everything you need to know to make sure you are getting the perfect model for your needs.
Type and functionality
There are two different types of phono preamps on the market, and each one is designed to work with the two different types of cartridges that are found inside of turntables. Before you purchase your phono preamp, you need to make sure you look carefully at your turntable, so that you are sure that you get the right phono stage for your needs.
MM (Moving Magnet) – Most of the newer style turntables utilize this type of cartridge. It does not require as much amplification as an MC cartridge. If you were to hook an MC phono to an MM cartridge, the sound would most likely be distorted.
MC (Moving Coil) – This style of cartridge has less output than an MM cartridge, which means that it requires more amplification. While you most certainly could hook up an MC cartridge to an MM phono, it probably wouldn’t be loud enough for you to hear it.
Thankfully, most single phono stages on the market can be used with both of these cartridge types. This will give you the ability to connect the right phono stage to either of these cartridges and get the quality of sound you desire. These models will usually have a small switch that allows you to switch between the two modes, based on the type of cartridge you are using.
The gain range of a phono stage describes the amount of amplification that it can create. Depending on the type of cartridge that you are going to be using, i.e., either MC or MM, you will need a different level of gain.
Thankfully, most phono preamps spell it out for you quite simply. Pretty much all of them will provide you with a minimum of 40dB of gain, which is usually plenty. Of course, if you are looking for an even bigger boost, you can always go for a model that gets you up to 45-50 dB of gain. This would probably only be for a turntable that uses an MC cartridge, as these require a bit more amplification than an MM one.
THD stands for Total Harmonic Distortion. This is a measurement system that is used to estimate the degree to which a system is nonlinear. A THD measurement is made by applying a sine wave as an input to a system, and measuring the total energy that appears at the output of the system, in comparison to the input frequency.
In more basic terms, the THD that is produced by a phono stage will help to predict how clear the sound quality is. The closer the THD measurement is to zero, the “truer” the sound is going to be, since there will be less distortion than if the THD measure was higher.
Phono preamps are rather complicated devices that are extremely easy to set up. All you need to get the job done with a phono stage are a few different cables and adapters, which will allow you to connect to both your turntable and a sound system.
You will need two sets of audio cables, so be sure that you look for a preamp that comes with them. These will allow you to connect your turntable to your phono stage, and your phono stage to your sound system of choice. You should also be sure to keep your cable length as short as possible and go no longer than five feet. The longer the cables, the more likely you are to encounter a loss of signal or sound distortion.
While it might be tempting to stick with as basic of a model as possible, there are lots of extra features to consider when you are looking at a preamp. As you have already read, some models can switch between MM and MC amplifying modes, which is quite handy if you have some turntables.
You should also look for a model that allows you to adjust the level of gain that the preamp will provide. That way, you will be able to create the exact sound that you desire, depending on what you are listening to.