DI Box & Phantom Power: All You Need to Know (+ Useful Tips)

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If you have been around microphones and used them for live programs and other applications, then you may have heard of the term “phantom power.” This is because condenser microphones require phantom power before they can work.

What about DI boxes? DI boxes are popular among recording and gigging instrumentalists, particularly bass players. Do DI boxes require phantom power before they can work as well? 

What is the relationship between DI boxes and phantom power? All of these questions and more will be addressed in this article, so read on.

What Is A DI Box?

DI boxes are also known as Direct boxes. These boxes primarily work by converting high impedance signals that are unbalanced into balanced low impedance format. 

This conversion is conducive for the transmission of audio signals into mixing consoles. DI boxes are used primarily for connecting to audio instruments such as guitars and keyboards. 

They can have single or multiple input and output channels.

Active DI Box

An active DI box is a DI box that needs to be connected to a source of power before it can work. This source of power can be either a battery or phantom power source. 

To connect an active DI box to a battery source, all you need is a 9-volts battery. On the other hand, you will need an XLR cable when you need to connect active DI boxes to phantom power sources.

Active DI boxes contain preamplifiers. This preamplifier increases the impedance and strengthens the audio signal that passes through it. They come with an active DI circuit as well. 

This enables active DIs to have a wider frequency response than passive DIs.

Passive DI Box

A passive DI box is a DI box that does not need to be connected to a source of power. Unlike active DI boxes, a passive DI box contains a transformer. This transformer performs balancing and impedance matching.  

It also preserves the frequency characteristics of audio signals that pass through them.

Due to the transformer they come with, passive DI boxes rarely add noise to audio signals that pass through them. Most passive DI boxes are engineered to have either ¼” or RCA phono input jacks. 

These input jacks enable you to connect instruments to the DI box. It also has a 3-pin male XLR output connection.

What Is Phantom Power?

Phantom power is simply a direct current sent through cables to operate audio devices with active electronic circuitry in them. These cables are usually microphone cables. 

Audio equipment that is known to supply phantom power includes mixers, preamps, and audio interfaces. 

Phantom power is popularly recognized as the way for providing power to microphones that depend on electricity for their operation. The type of microphone that requires electricity to operate is the condenser microphone.

However, condenser microphones are not the only audio devices that depend on phantom power to work. Phantom power is available in multiple voltage levels—however, most modern audio equipment supplies phantom power supply power of up to 48 volts. 

Phantom power is usually represented by a button on lots of preamps, audio interfaces, and mixers. Pressing this button enables the phantom power feature to work silently in the background.

Can a DI Box Provide Phantom Power?

DI boxes cannot provide phantom power. The primary design and engineered function of DI boxes do not give them the ability to supply phantom power to devices like condenser microphones.

The primary function of a DI box is to perform impedance conversion. It converts high-impedance audio signals that are unbalanced to balanced low-impedance audio signals. 

DI boxes also isolate and remove noise from audio signals. They also play a role when it comes to recording instrument signals and reamping. If you don’t know what reamping is, feel free to check out my article on how to reamp with a DI Box.

One thing you should note is that some DI boxes are powered by phantom power. DI boxes that are powered by phantom power are active DI boxes. 

Though these active DI boxes have an active circuitry that depends on phantom power to function, they cannot supply this phantom power to other devices that may need them.

In fact, DI boxes are known to prevent phantom power from being transmitted to audio equipment they are connected to. I will speak more on this later, so read along.

Do I Need Phantom Power to Power A DI Box?

Some active DI boxes need phantom power in order for them to work. Passive DI boxes, however, don’t need phantom power or any power supply at all to work.

As we have already talked about, active DI boxes require a power source in order for them to work. And depending on the DI box manufacturer’s preference, the power supply can either be a phantom power supply or a 9V battery. 

One of the more popular active DI boxes that require phantom power is Radial Engineering’s J48 DI Box (on Amazon). This DI box receives its phantom power from the mixer, stage box, preamp, or audio interface it is connected to. 

This power is transmitted by an XLR cable that is connected to the source. The phantom power provided is used for amplifying audio signals that pass through the active DI box. That is why active DI boxes come with preamplifiers in them.

How Do I Get Phantom Power to DI Box?

Phantom power is generally sent to DI boxes using an XLR cable. This cable must be connected to the XLR output of your active DI box and sent to the XLR microphone preamp input of your mixer board or preamp.

Phantom power has a nominal level of 48 volts. This gives the circuitry of the DI box more headroom, thus leading to lower noise generation.

When powering your active DI box with phantom power, you should pay attention to the level of voltage supplied by the source of the phantom power. 

This is because phantom power of lower voltage may not be able to power active DI boxes effectively. However, the great news is that most mixing boards supply 48 volts of power.

Will Phantom Power Damage a Passive DI Box?

Phantom power cannot damage passive DI boxes. A phantom power supply will not damage both active and passive DI boxes.  

In fact, an advantage of all DI boxes is that they isolate audio devices that can be damaged by phantom power when they are connected to them. 

When you put DI boxes between a mixer and these devices, these DI boxes shield them from any phantom power coming from the mixer.

When this happens, these devices do not receive any phantom power that has the potential to damage them. 

Most people don’t know that one of the functions of a DI box is to isolate electronic equipment that can be damaged by phantom power.

Thus, DI boxes isolate this electronic equipment from phantom power being supplied by the mixer or preamp they are connected to. DI boxes do this by blocking the phantom power transmitted from the mixing console. 

Therefore, the phantom power cannot interact with devices connected to the input of DI boxes.

In summary, though passive DI boxes are not powered by phantom power, they cannot be damaged when phantom power is passed through them.


DI boxes are designed mainly for connecting to audio instruments such as guitars and keyboards. These boxes do not supply phantom power to phantom power demanding devices like condenser microphones. 

Instead, DI boxes isolate devices connected to them from phantom power. Also, phantom power cannot damage DI boxes. 

However, just like condenser microphones, some DI boxes also require phantom power in order to work. DI boxes that operate on phantom power are known as active DI boxes.