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Recording your own original music is exhilarating. The opportunity to finally get your songs produced for the whole world to hear. But listen closely, because nothing stops the beat like unwanted buzzing, humming, clipping, crackling, and radio signal noises lurking in the background of your track.
That’s where a direct box comes in.
What You Need to Know About Direct Boxes
The best direct boxes, whether referred to as DI units, a DI box, or just “DI,” all serve the same main purpose: taking a high-output impedance unbalanced signal, and converting it to a low impedance balanced signal, typically through an XLR connector and cable.
Pretty much all electric instruments emit unbalanced signals. A direct box is used to connect your instrument to the input preamp of a mixing console for the purpose of recording, sound reinforcement, or playing live. When this happens, the signal is able to be sent through long cables without interference and with minimal loss of strength, giving you the sound you want, loud and clear.
When shopping for a direct box, “the only thing to consider is what you’re doing with it,” says Philadelphia-based audio engineer Brett Diamond. “For the most part, electric guitar players will want a passive DI, which is just a transformer that cancels noise, and they’ll want one that’s built like a tank. You want a fairly simple DI, mostly because you’re likely doing simple things with it. A DI box is not the unit in one’s collection to drop cash on bells and whistles,” he says.
Sources like electric guitars and basses are used with passive DIs that don’t require power. But for most instruments that are battery-powered or plug into the wall, active DI boxes are a better choice. These typically include a preamp for a stronger signal and higher input impedance, and usually feed off an AC adapter, batteries, or phantom power.
It may not look like much, but this small metal box automatically takes care of a lot of the most common issues, such as level matching, balancing, minimizing unwanted noise, distortion, and the annoying hum of ground loops. We’ve selected three solid choices to get you started recording and playing your music the way it was meant to be heard.
1. Radial ProD2 Passive 2 Channel Direct Box
This little green beast is solid, silent, and immediately eliminates any unwanted signal noise that’s been messing with your setup – both live and in the studio. Thanks to its two proprietary, custom-made transformers (one for each channel), issues like humming and buzzing from ground loops are instantly gone. So much, in fact, that a few users assumed their equipment’s power wasn’t even turned on the first time they used it.
While the inside does its job flawlessly, the outside is built to make sure it stays that way. Its protective front panel and baked enamel finish mean it’s ready for road life, continuous stage setups and tear-downs, and being knocked around in transport.
The Radial is a no-brainer for instruments like guitars and keyboards, but also great for laptops and iPads. With really anything that’s being wired up, the ProD2 makes sure only the sound you want is coming through crystal clear.
PROS: Super simple to set up, works instantly, no 9v battery or phantom power required, and features XLR inputs as well as ¼” inputs.
CONS: Features might be a little complicated at first.
2. Behringer Ultra-DI DI600P Professional Passive DI Box
From studio to stage and back, Behringer’s passive DI easily connects your guitar, bass or keyboard to a mixer, or to amps up to 3,000 watts. The device is built around Behringer’s OT-2 transformer, which flattens frequencies to quickly quiet down signal noise. With its parallel 1/4″ in and out jacks and XLR output, the DI600P sends out a balanced signal with minimal loss of quality (even with extra long cables), and eliminates most unwanted sounds in the process.
Any lingering hum is swiftly quashed by its handy ground lift switch, while the filter switch reduces annoying leftover hissing and buzzing. Another convenient feature is the Thru/Out jack, which lets you send a balanced signal routed to the mixer, while at the same time sending the unbalanced signal to an onstage amp. The DI600P may be a bit smaller than the others, but its solid metal shell still protects it from the hazards of touring just as well.
PROS: The Behringer is built well and a great choice, especially if you’ll need a few of them for your stage setup.
CONS: Based on factors like where it’s physically placed and the wiring of the building it’s in, users seemed to have mixed results with how much it quieted things down.
3. Whirlwind IMP 2 Standard Direct Box
Whirlwind’s IMP may be simple, in both looks and function, but it gets the job done, while remaining accessible. Built to last (people have had these for more than 15 years running) with a TRHL transformer that’s riveted to the chassis instead of glued, the IMP is in it for the long haul if you want it to be.
For those bands and musicians first starting out, constantly playing gigs, or throwing their gear around, this is an ideal piece for a first tour or studio setup.
While the IMP does what it’s supposed to – converting an unbalanced instrument signal to a low impedance, mic-level balanced signal – the biggest difference is that the IMP has one channel, while a DI like the Radial has two channels. So, it’s only able to receive one unbalanced signal in a TRS input, and send out one balanced in a XRS jack, while the Prod2 can handle two of those. Deciding if the IMP will fit your needs all depends on what you’ll be using it for. If you’re a solo recording artist at home, or a regular at the local open mic, this just might be your jam.
PROS: The extra ground lift switch on the side is a huge help when it comes to eliminating extra unwanted buzzing.
CONS: Low noise, but not necessarily no noise. A few users reported that the IMP’s conversion leaves a “muddy sound all around” and a “very rolled-off high-end.” Others say that while this is a great starter DI, upgrade when you’ve got the chance and the finances to do so.