Does a DI Box Really Reduce Noise?

If you often use microphones or electrical instruments, you have likely used a DI box. DI stands for direct injection, and these marvelous sound processing machines can convert your fuzzy-sounding audio output into a clear, balanced, high-quality sound wave. So, does it really reduce noise?

A DI box does really reduce noise. They convert high impedance signals into low impedance signals and balance your audio output, making it easier for your amp or mixer to isolate and remove extra noise like radio waves and resistance hums. The result is a cleaner sound.

In this article, we’ll discuss how DI boxes work and why they are so great at reducing noise. We’ll touch on why you might be hearing white noise on your audio tracks, and we’ll explore how DI boxes work. 

Active DI box to reduce noise
Active DI Box from Redial Engineering

Where Does Noise Interference Come From?

Whether you are a musician, recording artist, or microphone enthusiast, you know that your audio equipment will often pick up annoying humming sounds and white noise. This sound can come from radio waves, equipment like lights, ground loops, and the resistance of your audio cables. 

Before we get into the specifics of how a DI box works, it is crucial to understand the places that your white noise might be coming from. An unbalanced cable could result in too much noise or interference. Unbalanced cables have a hot wire and a ground wire. 

Unbalanced Cables

The ground wire surrounds the hot wire, like a sleeve, and protects it from interference from radio signals, the noise produced by your cable’s resistance, and the hum from other machines. Still, in longer unbalanced wires, the ground wire can act as an antenna and pick up radio frequencies from the air. 

Unbalanced cables longer than 3 ft usually pick up some static noise from nearby radio waves, TVs, hums from lighting systems, and other noise-producing instruments often used on stage and in the recording studio. Using a mechanism like a DI box can balance an unbalanced cable and reduce the amount of noise that the cord picks up. 

Balanced cables have three wires. Inside, they have a hot wire, a cold wire, and a ground wire. When you send audio through a balanced line, two copies of your sound will run through the wires. One copy is flipped in reverse, and the other runs straight through the cable. 

This flipping isolates the frequency of your audio output from any noise picked up by the line, which removes all of the extraneous white noise, giving you a clear sound. Another cause of noise interference is a ground loop. 

Ground Loops

Ground loops sound like a deep hum that occurs when you plug one piece of equipment into another. That noise occurs because one piece of equipment has a ground wire with a different voltage than the other equipment. Most musicians have gotten used to this sound, but DI boxes can eliminate it. 

What Does a DI Box Do?

When people started using electric instruments in the 1960s, they found that the signal was fuzzy, and it often picked up on hums from other machines and radio waves. To fight against this interference, they invented the Direct Insertion box or the DI box. 

DI boxes perform a multitude of tasks. If you’re unfamiliar with them, it can be challenging to understand why DI boxes are so advantageous. Let’s go ahead and review these worthwhile features.

Balance Your Signal

Firstly, DI boxes convert an unbalanced signal to a balanced signal. Most DI boxes have a tip-and-sleeve cable input for an unbalanced cable and an XLR cable output for a balanced one. By converting your unbalanced cable input to a balanced output, your sound will automatically cancel out any white noise. 

Since DI boxes balance your sound closer to the amp or mixer, they can allow you to use unbalanced cables that are longer than 20 ft (6 m) without hearing any noise interference. That can give you plenty of room to work, so DI boxes are essential for live performances. 

Convert High-Impedance Signals to Low-Impedance Signals

Impedance, often symbolized with the letter Z, is the total resistance of your whole setup, including capacitors, resistors, and inductors. Compressed or low-frequency sound waves have a low impedance, and audio waves with a higher frequency are high impedance. 

Most instruments and microphones emit a high-impedance, or high-Z, signal, but most amps and mixing machines require a low-impedance or low-Z signal. When you use a low-Z signal, you can use a long line since low impedance signals do not require as much energy to get from your input to your output. 

It is also easier for your mixer to isolate noise and cut it out of your audio if you use a low-impedance signal. Radio waves will appear at a much higher frequency than your audio output. 

High impedance signals often short out or drop off some sounds while the cable carries your sound output to a mixer or amplifier, especially if you are using long wires. High impedance lines are also more likely to pick up outside noises like radio waves since the audio waves have a higher frequency. 

Break Ground Loops

Most DI boxes have a setting called ‘ground lift’ that will eliminate any interference-causing ground loops in your instrument or microphones. Ground loops are a significant cause of hum and interference in audio outputs, and if you have ever used an amp, you have probably heard a ground loop. 

It is that buzzing sound you might hear when you power up your amp and connect an instrument. They happen when you have two pieces of equipment connected. 

Ground loops are caused when there is a voltage difference between your equipment. Using a DI box’s ground lift setting can adjust the ground voltage, reducing and potentially eliminating that annoying hum that you get when you power up your amp. 

Split Your Audio Output

Many DI boxes have a throughput connector, which allows you to feed audio through both a mixer and a PA system at the same time. If you want to work with a mixer in live shows, using a DI box is a great way to feed your audio through your mixer and back onstage without compromising your sound quality. 

Types of DI Boxes

There are two main types of DI boxes, and each one is better for different outputs. As a general rule, active DI boxes work with instruments and mics with passive out-lines, like guitar and bass. 

Passive DIs work best on actively powered equipment such as keyboards, electric drum kits, and microphones. 

Passive

Passive DI boxes are the most popular direct input boxes since they are durable and work best with instruments and mics with high-impedance outputs. 

They also don’t require a power source, so you won’t have to plug it in anywhere, which can be a significant benefit for live gigs. Passive DI boxes convert a high-impedance signal to a low-impedance using a transformer. 

This transformer is usually in an insulated metal box that keeps it from picking up noise. 

Active

An active DI comes with a built-in preamplifier, which can help you amplify low-impedance signals with clarity. They also provide extra gain. Gain can boost the frequency of your audio output, allowing you to use longer cables without experiencing any extra white noise.

Active DI boxes usually require batteries or another source of power to provide that additional gain.

Conclusion

DI boxes are essential for anyone who records sound or plays live shows. If you want to reduce the amount of noise that your amplifier or mixer picks up, using a DI box could be immensely helpful. 

A DI box can balance your sound, reduce ground loops, change your audio’s impedance, and split your sound without compromising it. If you want to sound your best, pick up a DI box and get ready for fuzz-free audio.