What’s the purpose of a preamp?

Often people starting out think that you simply need a turntable and some speakers and you can start playing music. What they are missing is that every turntable setup needs four essential components. A turntable, a preamp, an amplifier, and speakers. These components can all be external or can be built-in into one another. This is why every turntable setup is unique however they all need one essential component, a preamp. 

If you plug your turntable into an amplifier or receiver without using a pre-amp, you’ll have a very weak signal that results in a thin and tinny sound. Why? The signal produced by a cartridge is very weak. The signal need to pass through a PHONO pre-amplifier to become suitable for a standard audio input on a stereo. Also, a phono pre-amp would apply an equalization curve to inverse the standard frequency adjustment made during the record cutting process. In short, it boosts and converts the signal.

In this article, you are going to learn anything you need to know about pre-amps and how they work.

What does a pre-amp do?

As we’ve mentioned, a pre-amp does two things: (1) it amplifies the signal level so that it can be suitable for the stereo input, and (2) it applies an equalization that inverses the frequency adjustment made during the recording. 

1.   Amplification

When you play a record, the cartridge transforms a mechanical signal (the movement of the stylus over the record’s tracks) into an electrical signal. 

What actually happens is that there are grooves in a record in which the needle goes against causing resonance and thus, sound. However, as you can understand the sound from such a small needle is rather weak. 

The normal output level from a phono cartridge is 1 mV while the input on most stereos requires a signal level of about 100 mV. A pre-amp boosts the signal by 40-50 dB so that it becomes suitable for the Hi-Fi system input.

2.   Equalization

Records are made in such a way where the high frequencies boosted and the bass frequencies reduced. This is done to permit longer recording times since it helps keep the groove dimensions small while keeping a high sound quality. A phono pre-amp equalizes the signal. It boosts the low frequencies and reduces the high frequencies so that the sound is balanced.

The explanation above also explains the difference between a PHONO signal and a LINE signal. The weak signal that is produced by a phono cartridge is the so-called PHONO signal. This phono signal is weaker than a line signal and has reduced basses and boosted highs (for the reasons we’ve discussed above).

The pre-amp would provide a LINE signal: a signal 50 to 1500 times stronger than a phono signal and which has been equalized (called RIAA equalization) so that the sound reproduced has properly balanced low and high frequencies.

RIAA equalization is the process of the preamp equalizing the frequencies to the standard set by the Recording Industry Association of America. This became the general industry standard during the ‘50s.

How to set up your turntable and pre-amp

Setting up your turntable and preamp isn’t a difficult process as long as you know what you are doing. There are several setups possible that we will cover below but remember all need to have the four components, a turntable, preamp, amplifier and speakers. 

1.   Turntable with a built-in preamp

If you purchase a turntable with a built-in pre-amp (see advantages/disadvantages of built-in preamps later on), setting it up will be very easy. In this case, you can simply plug your turntable directly into your amplifier or active speakers. Active speakers have a built-in amplifier. This setup is often great for beginners and especially the turntables that have switch to bypass the built-in preamp are future proof as you can always add a better external preamp later on. We have made a list of what we consider to be the best turntables with a built-in preamp.

2.   Traditional setup

Back when vinyl records were the audio standard, most people had stereo receivers with a dedicated phono input in their houses. If you have one of these devices, you can set up your system as follows: connect the turntable to the stereo receiver via an RCA cable to the dedicated phono input. As the receiver already features a phono pre-amp you don’t need one built-in to your turntable or if you have a switch you can simply bypass it. 

This type of set up can work well when you have a lot of different audio types you want to want to play. Think of turntables, CD’s tape cassettes that can all be played on the same stereo system.

3.   Modular setup with an external preamp

If your amplifier doesn’t have a dedicated phono input, you can use the so-called modular setup. Here you connect your turntable to an external phono pre-amp.  This preamp is then connected to a separated power amplifier or active speakers.

This method seems a little more complicated than the previous ones, but it has the advantage of making it easier for you to upgrade single components down the line. Audiophiles always prefer this type of setup as it gives more control over the different components and thus the overall sound quality. 

If you are looking into external preamps because you don’t have one built-in or because you are looking to upgrade your setup to the next level, then look into our guide on the best affordable preamps on the market.

4.   Headphone setup

Once you’ve connected your turntable to a pre-amp, whether it is built-in or external, you can also connect it to a headphone amplifier and listen to your records with your headphones. A turntable with a built-in preamp or an external preamp will almost always feature a 3.5mm aux output to connect you headphones. This can be useful to those who share rooms or apartments with housemates.

Built-in pre-amp or external pre-amp?

As you know by now a preamp is needed in every turntable setup. A preamp can be an external device or can be built-in into turntable itself. Most of the turntables that have a built-in preamp also have an option to bypass it.

But what exactly are the advantages of a built-in preamp compared to an external one?

Advantages of a built-in preamp:

• Easier to set up and use. A built-in preamp has a clear advantage of not having to set up an extra device. You can plug your turntable straight into your receiver or amplifier. Even if it doesn’t have a Phono input. Or connect it with active speakers.
• Fewer sound issues. Sound issues such as a low hum, resonance or overall bad sound quality is often produced by one or more bad components or wires. Having a built-in preamp excludes the possibility of having such a problem within the preamp or its wires.

An external preamp generally has these advantages:

• Better sound quality. In most cases, external pre-amps can deliver higher sound quality compared to built-in preamps. In our experience, this is definitely true for the lower to midrange turntables where even a budget preamp can give a nice boost in sound quality.  
• More gain. An external preamp can be more powerful than a built-in one: while a built-in pre-amp rarely provides a gain of 60 dB, an external pre-amp can amplify the signal far further.
• More control. Audiophiles will often choose an external preamp as it gives them more control over the setup. They can choose the preamp and wiring and can adjust the sound via the separate components and button.

Whatever way has your preference, there are good options on either side.

If you are a beginner or occasional vinyl listener the best piece of advice we can share with you is to purchase a turntable with a built-in pre-amp that has the possibility to bypass it. This way you can start with the most simple setup and if you become passionate about records and vinyl, you can update your system with an external pre-amp to get an even better listening experience. We have mentioned a few options in our guide on the best turntables with a built-in preamp. Or if you are ready to take the next step in your turntable setup you can take a look into our favorite external budget preamps.