Pre-Out vs Sub-Out: All You Need to Know! Explained for Newbies

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If you are a new owner of a receiver or are now looking to purchase one, you have probably noticed two output ports labeled Pre-Out or Sub-Out. For those who don’t know what a pre-out and a sub-out are, this article is for you. After a few hours of research, here is what I learned about these two ports. 

The main difference between a pre-out and a sub-out is that pre-out is a port on an A/V receiver that is mainly used to connect the receiver to an external power amplifier. On the other hand, a sub-out is meant for connecting subwoofers to A/V receivers.

What Is A Pre-Out?

Pre-out ports are quite common on A/V receivers, especially on expensive receivers. Although some cheap ones may not come with any pre-outs at all, a lot of A/V receivers on the market today come with pre-out ports.

A Pre-out is a port on your receiver that enables you to connect an external power amp to your setup instead of using the receiver’s built-in power amp. This port allows an audio signal to pass through the receiver without amplification so that it can be amplified by another power amp.

A pre-out is used to connect an external amplifier to an A/V receiver. The speakers are then connected directly to the external amplifier instead of the receiver. This means that connecting an external power amp to your receiver’s pre-out port will allow a signal to pass through the receiver without being amplified.

With such a connection, the signal will be amplified by the external power amp that has been connected. An external power amplifier usually does a better job at amplifying audio than many receivers can.

Hence the presence of pre-out ports offers the possibility of adding separate power amplifiers in order to generate more power to drive your speakers. This puts less strain on your receiver. 

Having pre-outs on your receiver or integrated amp also allow you to improve your speaker system. So if you are on the lookout for creative ways to improve upon your speaker setup, using pre-outs is a great option.

I have a dedicated article that walks you through the process of how to connect a power amp to a receiver or integrated amp. I highly recommend you check it out if you’re planning to do this.

Pre-out ports are a valuable component to any A/V receiver, and you should keep that in mind when next you are looking for a new receiver. 

However, to acquire a powerful A/V receiver with lots of pre-out port options, you need to part with a great deal of cash. That notwithstanding, you will definitely get value for your money when you do so.

What Is A Sub-Out?

A sub-out is a special output on receivers meant for connecting to only subwoofers. Connecting your subwoofers using a sub-out port ensures that only the low bass frequencies are sent to the subwoofer and all the high frequencies cut off. 

The subwoofer output is actually the commonest way of connecting an active subwoofer to a receiver. Lots of home theatre receivers and some stereo receivers have a Sub-out port. You will normally see this labeled on your receiver as “Sub-out” or “Subwoofer.”

On most receivers and amps, there is going to be one sub-out connection; on some, there might be two.

However, you will only need one sub-out port to connect your receiver to a subwoofer. The subwoofer output is a line-level output that can be connected to your subwoofer using an RCA-type connection cable or an LFE cable.

If you have a subwoofer you want to connect with a home theatre receiver, just run an RCA interconnect cable from the receiver’s sub-out to the subwoofer’s line input.

Is Pre-Out Same As Sub-Out?

I believe at this point of the article, you should know what a pre-out and sub out are. But let me summarize everything so far in a few sentences. Is the pre-out the same as the sub-out?

Pre-out is not the same as a Sub-out. Pre-outs are used to connect A/V receivers to external amplifiers, while a sub-out is designed to connect receivers to powered subwoofers. Pre-outs are also designed to transmit all sound frequencies, while sub-outs are limited to transmitting bass frequencies only.

A sub-out has some form of bass management within the receiver that directs only the bass frequency in an audio signal to the subwoofer. On the other hand, a pre-out allows the entire sound signal to go to the power amp. This means a sub-out port has all the high frequencies cut, with just the bass signal filtering through.

Difference Between Pre-Out And Sub-Out

Although there are a few similarities between a pre-out and a sub-out, these two are completely different ports. What they have in common is that they are both output ports on receivers that are used to increase the output potential of your receiver. 

With these ports, powered speakers and subwoofers can be connected independently without needing the receiver’s amplifier.

It is worth noting that powered subwoofers connected to receivers using these output ports serve as both an external amplifier and a speaker. Now that we know exactly what pre-outs and sub-outs are, let’s look at their differences.

Pre-outSub-out
It serves as a port used to connect external amplifiers to an A/V receiver.It serves as a port for connecting to only a powered or active subwoofer.
They are designed to transmit full-range audio frequencies.They are designed to filter and transmit only bass frequencies.

Can You Use Pre-Out For A Subwoofer?

Although not ideal, you can use pre-out for a subwoofer, provided that the subwoofer has a built-in amplifier. The subwoofer will only play the bass frequencies delivered by the pre-out ports and cut off the high frequencies that can’t be played through them.

A sub-out port in a receiver is built to direct only the bass frequency in an audio signal to your subwoofer. On the other hand, a pre-out allows a full range frequency signal to go to your power amp (which, in this case, is your powered subwoofer). 

However, since subwoofers are designed to play only bass frequencies, the subwoofers will ignore all of the frequencies they can’t play and play only the frequencies they can play, which are the low frequencies.

Some receivers don’t even have any subwoofer output. If your subwoofer has no subwoofer output, you can still connect a subwoofer to it using a pre-out port. Pre-outs can be used with subwoofers that have their own internal amplifier.

Connecting your powered subwoofers to a pre-out is very simple. To do this, simply use an RCA-type input jack to connect from your receiver to your subwoofer.

What is a Sub Pre-Out?

On a few receivers and integrated amps, you’ll find an output port labeled sub pre-out? But what exactly is a sub pre-out, and how does it work?

A sub pre-out is a port on A/V receivers where some or all of the bass information in a signal is transmittedA sub pre-out is meant for connecting receivers to only powered or active subwoofers.

Technically, a sub pre-out port is the same as a sub-out. In the context of connectivity, they are no different since they are designed purposely for connecting subwoofers to receivers.

Some manufacturers may label the subwoofer connection port on their subwoofer as either sub-out or sub pre-out. However, sub-outs and sub pre-outs are basically the same. This is evidenced by the fact that most A/V manufacturers use the two interchangeably when talking about subwoofer connectivity in their manuals.

Both sub-outs and sub pre-outs are designed purposely to connect receivers to subwoofers. Powered or active subwoofers have external amplifiers inside them. Subwoofer pre-outs are used to connect to these external amplifiers that are present in subwoofers to an AV receiver. 

You can connect your active subwoofers to your subwoofer pre-out using an RCA cable.

Conclusion

Pre-outs and Sub-out ports add flexibility to your system and open your home theatre to many potential upgrade options. Using these ports is very easy, and learning how to do so will enable you to improve your home theatre or stereo systems considerably.

Sub-out is meant for connecting to subwoofers. Pre-outs, on the other hand, are meant for connecting receivers to external amplifiers, which will then power your speakers. Doing this will lessen the load on your receiver and allow your speakers to function at their maximum potential.