Line outputs and headphone outputs are two identical audio ports that are often confused with each other. This is not surprising since there is little information about them on the net. This article is going to shed more light on the two and the differences between them.
But what exactly is the difference between a Line Out and Headphone Out?
Line Out (or Line Output) is an audio port that is used to send line-level audio signals from one audio device to another. On the other hand, Headphone Out is an audio port that delivers an amplified line-level signal meant to drive headphones.
What is Line Out?
Line Out (or Line Output) is an audio port that outputs a line-level audio signal. Line out is also known as an Audio Out or a Sound Out.
Many people associate Line Outs with only keyboard, bass, or guitar amps. And that’s because those line outputs are usually labeled as “Line Out.” However, technically, you can think of any audio output that delivers line-level signals as a Line Out. This means you can think of the output of a mic preamp, mixers, keyboards and synths, and more.
Line Out allows you to send a line-level signal from one device to the other for further processing.
For instance, you can plug in a keyboard or guitar amp’s Line Out into the input of a mixer and then apply EQ, compression, or any other signal processing on the signal. And this is actually the most common way many people use Line Out. Or just as we talked about in our article on connecting guitar amp to audio interfaces, you can plug in a Line Out to an audio interface and record the amp’s audio.
This is a port that enables you to connect external speakers, headphones, and other output devices to your audio device. It basically allows you to transfer generated audio signals to these external devices so that you can hear the sound output.
Line out provides an audio signal output and is the music industry’s standard of signal transfer and the level expected for recording and driving amplifiers.
What is a Headphone Out?
A headphone out is an audio output that is primarily used to drive headphones. Headphone outputs have a built-in amplifier that boosts audio signals to a level that makes them audible in headphones. Although this is rare, some headphone outputs have watts of output power that is enough to drive powerful speakers as well.
A headphone output is derived from the line out audio stream. You can think of a headphone out as an amplified Line Out. What do I mean?
Basically, what a headphone out does is that it takes a line-level signal, routes it into an inbuilt headphone amp. This headphone amp then amplifies the line-level signal. And then, the amplified signal is then sent to headphones. This means headphone outs are at a stronger signal strength than line outs.
Difference between Line Out and Headphone Out
Line Outs and Headphone Huts are very similar, and most people cannot tell the difference between the two. But there are some key differences between the two. Let’s take a look at them.
Amplification and Volume Regulation
Line outs do not have amplifiers built into them and are not meant for driving headphones. A headphone out, on the other hand, has been incorporated with in-built amps. Some headphone outputs are even designed to have stronger amplifiers and are capable of producing higher voltage. This enables headphone outputs to deliver more power with little distortion.
When you use the line out of a device that has an inbuilt amp, the line out bypasses the device’s amp. However, when you use the headphone out of these same devices, the inbuilt amplifier works to amplify the signal strength being transmitted.
Line outs are meant to be connected to external amplifiers. And this external amplifier could be a headphone amplifier with a headphone out. Or it could be a power amplifier connected to a set of speakers.
Hence the volume of lines can only be controlled from the external amplifiers. With line outs, you may not be able to regulate the volume of the audio since this is meant to be done by the external amplifier it is connected to.
This means line outs have a fixed volume on the device they are found on. On the other hand, you can regulate the volume of a headphone output.
Output Signal Purity
As I mentioned earlier, headphone outputs are amplified line-level signals. Due to this, audio that goes through a headphone out will be subjected to another step of amplification, which may color the sound or add noise to it.
Some of these built-in headphone amplifiers are of low quality. Therefore, since a headphone out makes use of this amp, it can introduce another layer of noise and even distortion to your signal.
As a result, the sound from headphone outputs is usually slightly muffled compared to the clean sound from the line out. However, this noise may be quite hard to notice depending on the quality of the headphone out’s built-in amp.
On the other hand, line-level output signals are very pure. They are optimized to produce virtually little or no noise and distortion. This is because they are not subjected to any form of amplification that can introduce distortion in the audio signal. In theory, since line out signals are of low signal strength, they are less likely to get degraded.
Line out signals has a source impedance within the regions of 100 ohms and more. They are meant for driving loads that have high input impedance. Line level outs are optimized to produce low noise and distortion when used with high impedance loads.
Unlike line outs, headphone outs have a low source impedance. They come with impedance between 16 ohms and 600 ohms. Headphone outs are designed to drive lower impedances posed by headphones. Headphone outs are optimized to drive high current with reasonable distortion and noise with low impedance loads.
In conclusion, a headphone output is optimized for lower impedance loads and is capable of supplying more power to these loads. A line-out, on the other hand, is optimized for driving higher impedance loads.
Can I Use a Headphone Out as Line Out?
You can use the headphone output of your device as a line out. A headphone out can be used to send line-level signals to other audio devices, provided the volume is not too high. This will help prevent distortion and reduce noise.
Headphone outs can be used as substitutes for line outs. Some audio devices like keyboards, etc., may come with only a headphone out with no line output. As the owner of such a device, you would have no option but to use your headphone out as a line out.
Although headphone outputs are not as pure as line output signals, they can be used as line-outs without significantly reducing the final sound quality produced. This simply means it can give you good sound with just a little noise and distortion in performance. However, this result varies from one device to the other.
But as a rule of thumb, just keep the volume down. That’s because, I’ve already explained, headphone out delivers a much stronger audio signal that is louder than a Line Out signal. So reducing the volume will ensure you get an audio signal that is close to a Line Out’s volume. This will prevent any distortion and reduce any noise.
Though a headphone out can be used as a line-out, you can experience a little noise and distortion in the final sound output. This means you are more likely to get better and cleaner results with a line out. Even though you can use a headphone out as a line-out, I wouldn’t advise you to do so if you have a fully functional line output.
Can I Plug Headphones into Line Out?
You can plug headphones into a Line Out, but the audio will be barely audible, if audible at all through the headphones. That is because the audio signal through the line out is usually not strong enough to drive headphones.
Line outs carry line-level signals which are strong enough to be transmitted from one device to another with less to no signal loss. However, this is not strong enough to cause headphone voice coils to move back and forth to produce a sound.
This means when you plug in a headphone into a Line Out, you will probably not hear any sound. And even if you do, you will barely hear anything at all. Even if the audio is loud enough, the bass will be much reduced. Of course, all of these different issues will vary based on the headphones you’re using and the line Out of the device you’re plugging into.
But simply put, Line Out does not provide the needed amplification headphones require to work.
What Does Headphone Line Out Mean?
Headphone line out is a name given to a headphone output that can serve as a workable substitute for a line-level output. A headphone line-out allows headphones, external speakers, and other output devices to be connected to your speaker.
Technically, a pure line output will produce slightly better sound output than a headphone line out. However, nowadays, the difference is virtually negligible. This means headphone line outs can be used to drive headphones as well as line-level output loads.
A line out is a port for a line-level out signal. A line out is meant for connecting to external amplifiers, while headphone outs are meant for driving headphones. A line output provides an audio signal intended for further amplification by an external amplifier, while a headphone out amplifies a signal before transmitting it.
In summary, use a line out when you are not using headphones, and use headphone-outs for driving headphones.