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A direct box (“DI box” or “DI” for short) is one of the most powerful tools in any audio engineer’s arsenal. If you haven’t already, be sure to check out my earlier article, “What Is a Direct Box and When Do You Need One?” for an overview. But this time, we’re going to go dig into the two different types of DI boxes, the pros and cons, and when you should use each. So, what’s the difference between an Active vs. Passive DI Box? Let’s begin, shall we?
What Is a Passive DI?
Passive DI boxes use a transformer to convert electrical signal from the source instrument or audio device to a balanced signal, which you need for stable, long-distance connections. Make your input and output connection with no external power needed, run the cable as far as you need to your mixer, and boom… problem solved!
When to Use a Passive DI Box
Passive DI boxes really work best with active (powered) instruments and devices like keyboards, synths, samplers, and drum machines that generate line-level signal. They’re also great for outputs from a DJ Controller, electronic drum set module, consumer audio device, or laptop that uses 1/4” or RCA outputs — or at least a 3.5mm headphone out with a 3.5mm to 1/4” TS left and right interconnect cable OR an audio interface’s direct 1/4" outputs.
Keyboards, synths, and many types of samplers and drum machines have stereo outputs. That’s why I personally prefer a stereo DI box. That way you’re covered when someone uses specific instrument patches, custom sound design, and panning effects that take full advantage of a stereo setup.
(Excuse me for a moment while I put on my ‘90s infomercial salesperson’s hat…)
“And that’s not all!”
Don’t need anything in stereo? Well, now you have two separate mono channels available! Now you can run… say, two different keyboards in a more straightforward setup. Two channels in one box – what a bonus deal!
*Clears throat*
Okay, now where was I…?
Passive DI boxes are also much more convenient to use in a pinch. Maybe the audio interface for that home recording session doesn’t have any phantom power channels available, or the person running the mixing console at a venue is a volunteer who is only comfortable doing basic operations and would rather steer clear of dealing with phantom power?
Whatever the case, passive DI are plug-and-go for any instrument. Just remember if you use one with a guitar or bass, the gain at the mixer or interface source is likely going to need a bit of an extra boost.
What Is an Active DI Box?
Speaking of extra boost, it’s time to talk about Active DIs. Instead of a transformer, Active DI boxes include a dedicated preamp circuit. That means a stronger balanced output signal with more presence. But just like any active device, active DI boxes require a dedicated external power supply or phantom power from a mixing console or interface to operate.
When to Use an Active DI
Practically every electric guitar and many electric basses are passive, meaning that they don’t have any internal built-in preamps of their own. They send instrument-level signal, which is weaker than that sent by line-level instruments like keyboards. This is where an active DI box with its built-in preamp circuit to boost the signal can really shine!
Acoustic-electric guitars, orchestral string instruments with piezo pickups, and vintage instruments are also great candidates for an active DI. These often produce thinner and weaker signals that are helped immensely by the boost an active DI can provide.
The Radial PZ-DI Active Direct Box for Acoustic Instruments is a personal favorite of mine. It has a variable load selector switch for different types of pickups, which helps you dial in the sound with the right amount of drive.
DIs vs. Acoustic Preamp Pedal and Guitar Multi-Effects
There are lots of gear pieces that send signal from one place on stage or in a studio to another place, and it can be a bit confusing what does what. Like, what’s the difference between a DI and say… a preamp pedal or multi-effects box?
Well, the main difference between the two comes down to the final output signal. An active DI keeps the signal more “sonically neutral” or authentically colored based on the type of transformer inside. That makes them more straightforward for performers and gives the engineer a clean signal to balance, EQ, and add effects as part of the greater recording mix or front-of-house live performance mix.
Like an active DI, acoustic preamp pedals and guitar multi-effects have similar balanced outputs that can run to the interface or mixing console, but the difference is that they also contain many more tone-sculpting tools plus effects for the player to use live. That includes onboard EQs, boosts, reverbs, delays, and other features depending on the model. This gives a performer control over their sound before it reaches the engineer, plus they can work with amps or serve as the foundation for a standalone “ampless” setup.
Essentially, the DI gives the audio engineer the power, while guitar multi-effects give the player the power. They both can run balanced signal to the mixer.
Get Your Next DI from American Musical Supply
Direct boxes can open up so many possibilities, both on the performance stage and in any recording space. AMS is your stop for all sorts of active and passive DI boxes to suit you and your instruments. We have everything from popular favorites in a rugged stage box form factor all the way up to powerful professional studio-grade offerings and multi-channel rackmount units. You can’t get more “direct” than that!
