If you own an A/V receiver or a turntable, I’m sure you’ve come across input and output ports labeled “Phono” and Aux.” And this has many people confused. But what this the actual difference between and a phono port and and aux port. And which one should you use. This and more is what we’ll learn in this article. So let’s get straight into it.
What Is a Phono?
A phonograph connector, commonly referred to as a phono connector, used to be very popular years ago. Back then, it was used to connect phonographs to radio amplifiers.
Nowadays, phono is mainly used to connect turntables to phono stages. Phono ports come with metallic contacts and have the same connector design as RCA connectors.
That is why RCA connectors are also referred to as phono. The term “phono” represents both input and output connectors. This means that both phono in and phono out ports are referred to as phono connectors. However, phono inputs are more dominant in audio gears than phono outputs.
A phono out port is typically found on turntables and recorders. Audio signals from a phono out are very weak. These signals are low-level signals and can barely be heard out of speakers if they are not amplified. A phono out port is designed to send these weak audio signals to phono inputs.
A phono input primarily accepts signals from analog turntables. Thus, a phono mostly serves as the go-to port for connecting turntables to amplifiers.
Phono inputs are meant for receiving low-level audio signal inputs. Aside from the turntables and recorders that can be connected to phono inputs, other audio sources like CD players are high-level input.
Therefore, you can overload and possibly blow your phono input when you plug such music sources into them.
Phono inputs can be found among the connection ports on some audio equipment. Thus, phono inputs can be found as part of the ports on the rear panel of your mixer, amplifier, or preamp.
It is labeled as “PHONO.” A phono input comes with an in-built preamp known as a phono preamp.
What Is an AUX?
An Auxiliary port, commonly referred to as an AUX, is a port on amplifiers that receives or sends audio signals. An AUX port is used for interconnecting multiple audio devices.
An AUX connector or port can be either an RCA connector or a 3.5mm jack. Thus, cables that are plugged into AUX ports usually come as RCA or 3.5mm. However, the most common AUX connector is the 3.5mm male TRS jack.
Some high-end audio devices like the Yamaha soundbar have optical AUX connections. An AUX can be an input port or an output port.
An AUX-in is a port for input signals from devices with high-level output. Thus, an AUX-in receives audio signals from audio sources and mics. This type of port is common in older audio devices.
These audio sources include MP3 players, smartphones, iPods, CD players, etc. AUX-in receives audio signals from line-level outputs.
Audio devices with line-out can be connected to the AUX-in of an amplifier or stereo. You can also connect the headphone jack of your smart device or audio player to the AUX-in of your stereo by using an Auxiliary cable.
To use an AUX cable, simply plug it into your portable device’s headphone jack and connect the other end to your stereo’s AUX input. AUX inputs are found on stereo receivers.
Nowadays, most car stereos have Bluetooth and USB inputs. However, some car stereos still come with an AUX input. Thus, common modern-day use of an AUX cable is the connecting of smartphones to car stereos through this AUX input.
An AUX-out sends audio out of an amplifier and into a speaker. It enables you to connect external speakers to your amplifier. Audio signal from an AUX out can also be sent to a recording device or a PA system. An AUX out sends out a copy of the audio signal transmitted by the line out of an amplifier.
Difference Between Phono and AUX
Built-in Preamp and EQ
Phono inputs are engineered to have a special preamp built into them. This preamp is known as a phono preamp.
The preamp in the circuit of phono inputs enables them to boost the signals that pass through them. Phono inputs come with internal EQs as well. This EQ is known as the RIAA equalization curve.
On the other hand, AUX inputs do not have any form of amplification built into them. Thus, AUX inputs do not boost audio signals that pass through them. AUX inputs do not have any form of equalization in them as well. This is the main difference between phono and an AUX.
The sound from a phono output is relatively low. This is because the signal strength of audio signals transmitted from phono outputs is very weak. The output voltage of phono outputs is about 2.5millivolts.
Due to this, audio signals from a phono output need to be amplified by passing it through a preamp. This is the main reason why phono inputs have built-in preamps.
The purpose of this preamp is to boost and strengthen the weak signals into a line-level signal transmitted from phono outputs. This boosting enables us to hear audio signals transmitted by a phono output.
An AUX is basically a line-level input. The output voltage of an AUX connector can reach as high as 1 volt.
Therefore, audio signals transmitted from an AUX output are stronger than the signal transmitted from a phono output. These signals do not need further amplification before they can be heard clearly from speakers.
They have EQ curves built inside them. The presence of this EQ introduces coloration into the audio signals that pass through it. This affects the purity of the audio signal.
Just as I have mentioned throughout this article, phono inputs have built-in preamps as well. This preamp amplifies audio signals that pass through the phono input.
Anytime an audio signal is subjected to amplification, some form of noise gets introduced into the signal. This affects how clean the audio signal is.
Therefore, the presence of an EQ and preamp in phono inputs negatively affects the quality of the audio signal.
On the other hand, AUX inputs have no EQs in them. They have no preamp in them as well. This means AUX inputs do not amplify and color audio signals. Thus, AUX inputs transmit clean signals. They transmit the same signals that they receive.
This doesn’t necessarily mean that audio from phonos sounds bad. In fact, you may not notice any coloration or noise in the audio signal from a phono out. However, just know that preamp and EQ will affect the sound.
Can I Use an AUX Input as Phono?
You can use an AUX input as a phono, provided the turntable you are connecting it to has a built-in phono preamp. To do this, simply connect your RCA cables from the turntable to your receiver’s AUX input.
However, in order to effectively use your AUX input as a phono, your turntable must come with a built-in phono preamp. Alternatively, you can use a standalone phono preamp if your turntable does not have a built-in phono preamp when using your AUX input as a phono.
Audio signals from turntables are quite low. Hence, when you plug turntables into line-level input like an AUX input of your receiver, you will only hear a tinny and faint sound.
This is because when these audio signals are transmitted through the signal pathway to speakers without any form of amplification, you will barely hear any sound.
Therefore, audio signals from turntables must be preamplified before it gets to your receiver. This will enable us to hear these audio signals.
The amplification of audio signals from a turntable is done by a preamp. This preamp is known as a phono preamp. Phono connectors come with a built-in phono preamp. Some turntables come equipped with this built-in phono preamp as well.
Unfortunately, AUX inputs do not have this built-in phono preamp. Therefore, when using AUX inputs as a phono input, you must make sure your turntable has a phono preamp of its own.
In the event that your turntable does not have a built-in phono preamp, you will have to use a standalone phono preamp. This will enable you to hear the final audio signal output from your turntable.
A simple and inexpensive phono preamp such as the Rega Fono A2D Mini (on Amazon) can easily get the job done if your turntable doesn’t have a built-in phono preamp.
Not only does this phono preamp boost the weak signal from your turntable into a line-level signal, but it is also an Analog-to-Digital converter.
Can I Connect an AUX to A Phono Input?
It is not advisable to connect an AUX output to a phono input. This is because connecting an AUX to your phono input will overload your phono input circuitry. This can cause damage to your speakers and amplifier.
A phono input is designed to receive weak signals. That is why it comes with a built-in preamp for amplifying these weak signals it receives. AUX outputs transmit line-level audio signals.
These signals are relatively stronger than the signals transmitted by phono outputs. Therefore, when these line-level signals from an AUX enter a phono input, it overloads the phono input’s circuitry.
Amplification of these strong line level signals by the phono’s built-in preamp will produce an even stronger audio signal. This will overburden your amplifier and speaker, which can cause them to get damaged.
In the event that your system does not get damaged, the sound you will receive will not be as clean as the original signal coming from the source.
This can be attributed to the fact that a phono input port comes with a built-in EQ and preamp. Thus, the audio signals that pass through phono inputs receive some amount of signal boost and EQ coloration.
In plain terms, phono inputs always apply equalization and amplification on any signal that passes through them.
The coloration and amplification that is applied by phono inputs on audio signals ultimately affect the nature and quality of the output signal. This alters the purity of audio signals that pass through phono inputs.
Therefore, though you can use a phono input as an AUX input, the sound quality will not be as great as that you would get from an actual AUX input.
In extreme cases, you may end up damaging your amplifier and speaker when you do so.
In summary, a phono is designed to receive weak signals. Phono inputs come with built-in amplification and EQ for boosting and coloring these weak signals. On the other hand, an AUX is a line-level signal port.
Thus, it is meant for receiving high-level audio signals. An AUX does not have built-in amplification and EQ.