DI boxes

Direct boxes (also known as DIs, which stands for “Direct Inject”) began as a way to resolve a basic impedance mismatch between electro-dynamic guitar pickups (high impedance unbalanced) and sensitive studio electronics (quite low impedance balanced). Still today the primary function of DI boxes is to take an unbalanced, high-impedance signal and convert it to a balanced, low-impedance signal. This allows to send audio signal over extended cable runs without losing volume, high-frequency information and without picking too noise easily. DI boxes are essential pieces of stage equipment.

Mixing-console mic inputs in a live-sound context typically expect to handle signal levels from maybe as low as -55dBu, up to about +5dBu. Microphones generally have a very low source impedance of about 150Ω, from a balanced source, and expect to see a load impedance of about 1.5kΩ or higher. The output of an electric guitar is unbalanced, with a typical level range of between about -30 and 0dBu, perhaps going up to +10dBu for active basses. The source impedance is relatively high, at between 5kΩ and 20kΩ for normal electric guitar pickups (can be higher for special pickups and piezo). The load impedance to which electrical guitar should see should be much higher than it’s output impedance, anything up to 1MΩ is common. The load impedance can affect electrical guitar sound. Usually, the instrument to be DI’d will be connected to a local amplifier/speaker combo on stage, so some kind of signal splitting and feed-through provision is generally required.

Modern passive DI boxes typically use a transformer to convert high-impedance signal to low-impedance balanced signal. This style of transformer features electrically separate windings in the input and output stages, which can isolate ground-level voltages and eliminate ground loops. Typically a switchable ground lift lets you disconnect Pin 1 on the XLR jack of the DI box. Some DI boxes feature a switchable attenuator (called a pad) and/or “phase” switch to polarity reverse audio signal. Usually the input impedance of passive DI boxes can be up to few tens of kilo-ohms (up to about 150kΩ). Passive DIs typically are stepping down the signal voltage by about 20dB in unbalanced-to-balanced conversion.

An active DI includes a preamplifier which can provide a very high input impedance and also can usually provide an extra gain to boost the weak signals. Active DIs requires power, which can come via batteries, dedicated power supplies, or 48V phantom power, depending on the model. A good active DI can presents a high-impedance load (>250kΩ) to an unbalanced instrument source. Active DI boxes employ an active electronic buffer circuit at the instrument input to present a very high input impedance to the source instrument — typically 1MΩ or so. This allows the guitar pickups to work as intended in delivering the expected tonality and sustain.

The differences between DI boxes basically come down to build quality and ruggedness, the design of the electronic circuitry (especially the power supply arrangements), the features and facilities included, the headroom margin, and the quality of the transformer.

As direct boxes have evolved and many similar tools have entered the market, a number of devices similar to direct boxes have become available. This group of devices include in-line preamps, attenuation pads, isolation transformers and re-amping boxes (opposite function of DI).

Tutorial: DI Boxes & You

DI boxes part 1: What does a DI box do, and when do I need one?

DI boxes part 2: Active vs. Passive

DI boxes part 3: Amplifier DIs – using, advantages and disadvantages

DI Boxes Part 4: Stompbox/Pedal DIs

DI Boxes Part 5: Active vs. Passive revisited

Peter Janis explains the Pro-D2 passive stereo direct box

Radial j48 advanced active direct box – explained

How to Choose a DI: Active vs. Passive

The Radial JDI explained

PZ-DI – Peter Janis of Radial Engineering

Using a DI Box for Acoustic Guitars – AudioTech

How to hook up and use a D.I. Box with acoustic guitar setups.
Radial-JDX-explained.mp4 – Peter Janis talks about how the JDX works and why.

Peter Janis talks about the Radial JDX amplifier direct box with speaker emulation.
AV Genius “How to Mix” series – What is a Direct Box ?

How to Choose a DI: Active vs. Passive

Guitars and Gear Vol. 42 – Radial PZ-DI Piezo-optimized Direct Box Demo

Behringer DI20 UTRA-DI Duel Direct Box Review

I have several active DI boxes, and the Behringer ULTRA-DI DI20 is the worst one. Too noise, to much hiss, even using batteries (easily audible in a simple DI comparison). So it results in a very very poor signal / noise ratio.
STAGE TUTORIAL Beginner How to Use a Direct Box for Acoustic Guitar

Radial Engineering USB Pro Digital Stereo DI for Laptops Overview | Full Compass

Radial Engineering’s USB-Pro makes it easy to connect to your computer, iPad or iPod to a PA system. You simply connect via the USB port and the USB-Pro delivers stereo balanced outputs via the dual XLR connectors.
#016 Passive Direct Box Stop Motion Teardown

DI BOX Test (DI20, Handmade DI – Hansen schematic, Audient iD14)

Build Your Own Passive DI Box (easier than you think)

diy di box from old modem transforme

Simple DIY Passive DI Box Circuit Version 2


  1. Tomi Engdahl says:

    Troubleshoot and Eliminate AC Hum on Sound System

    This video explains common causes and troubleshooting and eliminating techniques for AC Hum on Sound Systems.

  2. Tomi Engdahl says:

    Connecting Guitar & Bass Using DI Boxes

    Connecting electric guitars and basses to a mixer that doesn’t include a DI box.

  3. Tomi Engdahl says:

    1M input impedance with active buffer is important aspect of most DI, 10M is needed for piezo pickups.

    15k would be fine from an electronic keyboard, but it’s a bit low for a guitar or bass. From an acoustic guitar with electronics inside (like an Ovation), it would be fine.

  4. Tomi Engdahl says:

    DI Boxes, Impedance and Transformers Part #1

  5. Tomi Engdahl says:

    Joyo ZGP Noise Blocker

    Eristää huminaa, kohinaa, ylikuulumista ja maasilmukoita eristämättömistä virtalähteistä ja signaalipaikoista
    Muuntaa monen virtalähteen todelliseksi itsenäiseksi päivänkakkara-ketjun lähtötehoksi
    Suodattaa virtalähteen aaltoilevan melun
    Katkaisee maasilmukan ja tarjoaa itsenäisen lähdön vakaalla 9 V: n lähtöjännitteellä
    Tulojännite: 9 V DC

  6. Tomi Engdahl says:

    DI Boxes, Impedance and Transformers Part #1

    Part 1 of Chatting about DI boxes, impedance and such

    DI Boxes, Impedance and Transformers Part #2

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  7. Tomi Engdahl says:

    Direct Injection Box for Recording & PA Systems

    A Direct Injection (or DI) box is a very handy piece of equipment for any public address rig or recording studio, whether for band or general use. It will allow you to connect the output from guitar amps, keyboard mixers, tape machines, CD players and just about anything else directly to the mixer, without using a microphone, and with no hum loops.

    The unit described will convert unbalanced inputs (such as from a guitar or bass amp) to balanced, allows the level to be set to something reasonable, and comes in two flavours. There is a completely passive version that uses a transformer to create the balanced send, or an active unit which can be operated from a 48V phantom feed or a 9V battery.

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    What Is A DI Box (Direct Box)? | When & How To Use One

  9. Tomi Engdahl says:

    Rupert Neve RNDI Direct Box | Best DI Box For Bass & Guitar

    The Rupert Neve RNDI direct box is one of my favorites, especially for guitar and bass! Hear the RNDI for yourself in this video!

    0:00 – Introduction
    0:16 – The Rupert Neve Sound
    0:53 – Demo: Whirlwind IMP 2 vs Rupert Neve RNDI
    1:40 – Specs & Features
    3:29 – Demo: Rupert Neve RNDI (Post Guitar Amp)

    Viewer comments:

    DIs are a perfect option too when you want to record both the amped and direct sound to make decisions about the blend in the mixing stage, possibly processing the direct signal too.

    And regarding the feature that allows getting the real high power signal from the amp, that is amazing. I got the Countryman Type 10 and it allows the same too. I confess I haven’t used that option yet.

    Well, in the first demo I heard absolutely no difference at all. But the speaker input feature is a nice thing. And usually I simply use the integrated balanced out of my bass amp.

  10. Tomi Engdahl says:


    The Detroit Sound

    During Motown’s heyday, a major technical component of “The Detroit Sound’ was the direct input box (DI). Designed by a young Motown audio engineer in the early 1960s, the musicians plugged straight in and achieved a distinct, colorful distortion that would become recognizable all over the world. The DI box was adopted by such Motown greats as James Jamerson Sr., Dennis Coffey and Bob Babbitt, who defined the sound of a generation with their soulful playing and crisply captured notes.

    Recreated by Acme Audio, the new Motown D.I. WB-3 brings the exact character as the original DI box. Modern updates include the improved variable attenuated for high-level input and the custom-made, rugged steel case (the original DIs were built in Aluminum boxes). Owners of the Motown DI will find that it increases sound quality in a marginal acoustic environment, for the cleanest, purest sound source possible.

  11. Tomi Engdahl says:

    DI Box – What is it and how to use it? Direct Box 101 – Passive or Active? Which should you use?

    What is a DI and do you need one? Active or Passive DI? This video explains the differences and shows connection diagrams and important information.
    A DI, which means Direct Injection (DI Box), allows you to connect your instrument to the balanced inputs of a mixer of a sound system, or to a recording console in the studio. While standard instrument cable is susceptible to noise after a few feet of length, balanced signals can remain relatively noise free over even hundred’s of feet. That makes them perfect for connecting acoustic guitars, synthesizers, and bass guitars to a sound system or recording desk / DAW. Even when the mixing desk is a 100′ or more away from the stage. Also discussed is the ground lift switch for defeating ground loop noise, hookup cables, and best practices for using a DI.

    A DI box is also useful when tracking guitar in you DAW so that you can record a second, clean track, along with your mic’ed amplifier. The clean track then can be re-amped later should you decide you don’t like the sound of the original mic’ed amp.

    Various models and budget ranges of DI’s are shown in this video. This includes a workhorse like the passive Whirlwind IMP-2, the industry standards Radial JDI and Radial J48, Radial’s budget offering the Radial ProDI, a past industry standard active DI- The Countryman Type 85, and the active Behringer Ultra DI.

  12. Tomi Engdahl says:

    Can YOU hear the difference? Blind Bass Direct Box Shootout

    In this video, I share a blind comparison test with seven different direct boxes for electric bass. Together we compare the Radial JDI, the JHS Colourbox, the Noble, the Reddi, the Zod, the Ampeg SCR-DI, and the Pyle. We discuss the value and results that bass direct boxes have on bass tone.

  13. Tomi Engdahl says:

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  14. Tomi Engdahl says:


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  15. Tomi Engdahl says:

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    In the YouTube video titled “What Does Audio Transformer Overload Sound Like?”, the speaker demonstrates the effects and sounds of an audio transformer overload, testing various audio transformer boxes, and battling with mixing consoles clipping while testing. The video also examines the difference between using a mic level or line level transformer for low-level signals and tests whether a line level transformer for a mic level signal causes any impact or distortion. The speaker concludes that the mic level transformer will only cover low-level signals, whereas the line level transformer can cover the entire scope of low to high levels, and while it may cost more money, it can be more useful in the long run. Overall, the demonstration shows how to listen for distortion and overload in audio transformers.

  16. Tomi Engdahl says:

    What Are Audio Transformers? Why Do They Sound So Good?


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