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Direct Box Basics

Radial JDI direct boxDirect boxes are something that we use every day in recording, yet take for granted because of their simplicity. Here’s an excerpt from my Recording Engineer’s Handbook that looks at the ins and outs of this useful recording tool.

“Direct Injection (DI or “going direct”) of a signal means that a microphone is bypassed, and the instrument (always electric or electrified) is plugged directly into the console or recording device. This was originally done to cut down on the number of mics (and therefore the leakage) used in a tracking session with a lot of instruments playing simultaneously. However, a DI is now used because it either makes the instrument sound better (like in the case of electric keyboards) or is just easier and faster.

Why can’t you just plug your guitar or keyboard directly into the mic preamp without the direct box? Most preamps now have a separate input dedicated for instruments, but there was a time when that wasn’t the case and plugging an electric guitar (for instance) into an XLR mic input would cause an impedance mismatch that would change the frequency response of the instrument (although it wouldn’t hurt anything), usually causing the high frequencies to drop off and therefore make the instrument sound dull.

Advantages of Direct Injection
There are a number of reasons to use direct injection when recording:

  • Direct Box transformers provide ground isolation and allow long cable runs from high impedance sources like guitars and keyboards without excessive bandwidth loss.
  • The extremely high impedance of the DI insures a perfect match with almost every kind of pickup to provide a warmer, more natural sound.
  • The length of cable can be extended up to 50 feet without signal degradation.

Direct Box Types
There are two basic types of direct boxes; active (which can provide gain to the audio signal and therefore needs electronics requiring either battery or AC power), or passive (which provides no gain and doesn’t require power). Which is better? Once again, there are good and poor examples of each. Generally speaking, the more you pay the higher quality they are.

An active DI sometimes has enough gain to be able to actually replace the mic amp and connect directly to your DAW.

An excellent passive DI can be built around the fine Jensen transformer specially designed for the task (www.jensen-transformers.com for do-it-yourself instructions) but you can buy basically the same thing from Radial Engineering in their JDI direct box (see the figure on the left). Also, most modern mic pres now come with a separate DI input on a 1/4” guitar jack.

Direct Box Setup
Not much setup is required to use a direct box. For the most part, you just plug the instrument in and play. About the only thing that you might have to set is the gain on an active box (which is usually only a switch that provides a 10 dB boost or so) or the ground switch. Most DI’s have a ground switch to reduce hum in the event of a ground loop between the instrument and the DI. Set it to the quietest position.”

You can read more from The Recording Engineer’s Handbook and my other books on the excerpt section of bobbyowsinski.com.

New Music Gear Monday: Creation Labs MW1 Studio Tool Guitar DI

MW1 Studio ToolRecording guitars in the control room has become standard procedure during overdubs these days, but there always a hassle to it. Ground loops, amp noise during tuning, and not having the amp head close by to change the tone or input gain are minor inconveniences, to be sure, but inconveniences none the less. That’s what makes the Creation Labs MW1 Studio Tool so cool; it eliminates all those hassles at once plus adds a few extra features.

The MW1 Studio Tool is basically a DI on steroids in that it goes way beyond what a normal direct box does. Developed in conjunction with the excellent producer/engineer Michael Wagner, the 1U rack space unit is at heart a transformerless direct box with a few twists. First of all, it has front panel  1/4″instrument input jack coupled with a variable input impedance control that really changes the tonal character of the guitar a lot more than you might think (see the video below to hear how much). There’s also a 1/4″ tuner output jack along with a mute switch that mutes the throughput through the box but keeps the tuner output active for silent tuning.

Then the cool stuff really starts. The next section provides a control for the amp output with up to 30dB of gain along with an output impedance control to further tailor the tone going to the amplifier. There’s also a front panel 1/4″ output jack for this section that’s intended to be plugged into an amp.

The next section is the balanced mic level output level complete with a polarity control and signal indicator LED.

Recording both a guitar DI and amp signal simultaneously makes it a lot easier to edit a distorted guitar, but what if you want to reamp the clean direct signal later? The next section of the MW1 is dedicated to reamping with a balanced line input control that provides up to 36dB of attenuation coupled with an another output impedance control and a front panel 1/4″ output jack.

The rear panel duplicates the front panel 1/4″ inputs and outputs and holds XLRs for the the DI out and reamp input. There are also ground switches on the input and output as well as for the MW1 to help rid you life of those nasty ground loops.

The Creation Labs MW1 Studio Tool is one of the most versatile boxes out there and something you’ll use on every guitar overdub or during tracking. It’s not cheap at $795, but if it’s something that you’ll use a lot and will save you some time and eliminate even a hassle a day, it’s worth every penny. Creation Labs also offers a two week free trial.

Check out the video below that demonstrates how the MW1 works.