Do I need a DI Box for live Guitar?
Do you know what a DI box or a direct box is and what it’s used for? The day will come. Someone will ask you “Do you need a DI box?”. Or worse, “Do you HAVE a DI box?”. It’s not rocket science, a DI box is a small and simple gadget that can save your show when playing guitar, bass, or keyboards.
We guitarists are always talking about guitars, pedals, and amps. We can sometimes (most of the time) get obsessed with guitar gear. But do we ever hear us debating over DI boxes? No. It’s because most of us don’t know exactly what they do, just sort of.
So if you’re a member of that club or if you are a total beginner to all related to DI boxes, you’re in the right place. Let’s explain all the basics about DI boxes: what they are, what they are used for, and who can benefit from using them.
Key takeaways:
- DI boxes are used to convert instrument audio signals to mic-level balanced signals that mixers work with
- Main benefits: Consistent and uncolored sound, no unwanted noise, long cable runs
- Di boxes provide us with professional sound gig after gig
- Best for Acoustic, bass, and ampless electric guitar players
Essential terminology
Impedance
Impedance is measured in ohms. It tells us the amount of resistance a piece of gear has to an audio signal which is measured in volts. Guitar signal has a high-impedance output which means it can’t travel effectively through very long cables because there is more resistance.
On the other hand, a microphone signal is low-impedance and can travel through long cables without losing quality.
Balanced vs unbalanced
Unbalanced cables are used for instruments like guitars, basses, and keyboards. These cables have two conductors (wires): a signal wire and a ground wire. They work well for sending signals up to 6 meters. But since the ground wire picks up noise anything longer than that can become a problem. A TS (tip-sleeve) ¼ inch guitar cable is the typical unbalanced cable used by musicians.
Balanced cables are typically used for microphones. This type of cable has one extra signal wire, for a total of two signal wires and a ground wire. Without going into detail about how it is done, a balanced cable does a great job of rejecting noise and can be used to send signals for up to 100m (300ft).
A logical question is: “Why are balanced cables used for microphones for distances less than 6m?”. Microphones produce the lowest signal level. If we were to use an unbalanced cable for a microphone signal, the noise that would be picked up would be much stronger relative to the mic signal than to an instrument signal.
After that, we could ask: “Why don’t we use balanced cables for every signal if it’s better at rejecting interferences?” The most obvious answer is because of the cost of balanced cables.
Typical balanced cables are XLR “microphone” cables and TRS (tip-ring-sleeve) ¼ inch cables
What is a DI box?
First of all, let’s explain what DI stands for. The DI stands for “direct injection”.
When playing live gigs we connect all instruments into a mixer where we balance and enhance the overall sound that is then sent to the PA. The mixer has to “communicate” with the signals from the instruments in the same language. In other words, the instrument signals have to be compatible with the mixer.
Mixers are designed to receive mostly microphone-level signals and some line-level signals. The level of an audio signal refers to its voltage. Microphones are used for vocals, mic’ing guitar amps, and any other instrument like a drum set or a saxophone. These low-impedance microphone signals are exactly what a mixer expects.
But in some cases, sending the signal of an instrument through microphones is not an optimal or possible solution. This is where DI boxes come in place.
Di boxes are devices that convert audio signals to the signal type that mixers “understand”. Think of them as translators. Not all instruments have the same type of output signal. That is the reason why there are so many different types of DI boxes.
Guitarists usually use this signal flow:
Guitar > pedals > amplifier > microphone (in front of amp’s speaker) > mixer.
But sometimes you want to send your guitar’s signal to the mixer without an amp in the signal flow because you are using an ampless guitar rig (with no speaker to be mic’d or your amp isn’t working. For that scenario, you should be aware that guitars produce an instrument-level, high-impedance, and unbalanced output which a DI box converts into a mic-level, low-impedance, and balanced signal that mixers can work with.
Without going into detail we need to understand the correlation between different audio signal types. These are the four audio signal types positioned from weakest to strongest signal.
- Microphone level
- Instrument level
- Line level
- Speaker level
A DI box is a device that changes the guitar’s signal to the signal type that mixers accept.
Benefits of using a DI box for your guitar
Clean and uncolored sound
DI boxes provide mixers with your guitar’s original and uncolored sound. Since it is sending a balanced signal there is no unwanted interference being picked up by the use of long cables, and the signal’s strength is stable at all times.
Consistency
When playing at different venues we notice that some venues have issues with electrical and sound installation. Using a DI box will ensure that your instrument’s sound quality is consistent wherever you play.
Routing flexibility
Not all guitarists route their guitar signals the same way. Some need to split their signal in different directions. Many specialized DI boxes are tailored to various routing combinations making them versatile audio tools. The most popular routing type is where a DI box has two outputs, one for your amp for stage monitoring (instrument cable) and the other for the FOH (XLR balanced output). This way you have full control of your sound on stage independently of the sound that is sent to the FOH.
Ground loop hum elimination
You never know when that annoying hum will start. Most DI boxes have a ground lift switch. Its purpose is to isolate your instrument’s signal from the grounding system of the venue you are playing. Simple and helpful.
Long cable runs
Balanced cables are capable of sending audio signals up to 100m (300ft) distances without losing quality and picking up interference.
When should you use a DI box?
Ampless guitar rig
Many modern guitarists and those who want to downsize their guitar rig are playing without amps. Since there is no microphone involved a DI box is needed to convert the guitar’s signal to a mic-level signal that the mixer can optimally work with.
The DI box can be used as a separate unit but all guitar processors with amp and cab simulations have a Line-level output that can be used directly into a mixer’s line input. Just be sure to adjust the output settings to “line” instead of “instrument”. Larger guitar processors and multi-effects also have an XLR mic output suited for mic inputs on a mixer.
Large productions
When the main mixer is located far from the stage a snake is used to transfer all the signals more easily. Although microphone cables are balanced and can send clean signals much further than instrument cables, there is always room for interference. If we use a classic guitar rig with a mic’d amp it’s always a good idea to use a DI box as well. The DI box will give more stability and control of your guitar’s signal.
Cabinet simulation
If you are using an ampless guitar rig, you will need a cab sim somewhere in the signal flow. It can be located in your multi-effects unit, dedicated pedal, or in a DI box. The fact is that there is no microphone involved so we have to use a DI box. Radial makes some of the best DI boxes and some of them are equipped with a cab sim.
Acoustic guitar
Acoustic guitar players usually play without an amplifier for acoustic guitar. In those cases, the acoustic guitar is skipping the microphone that electric guitar players use. You can plug an acoustic guitar directly into a mixer but never into a microphone input, it is too sensitive. If going directly to a mixer always plug an acoustic guitar into a line-level input and make sure the instrument cable isn’t longer than 3 meters. Anything longer than that will pick up lots of unwanted noise.
Remember the four signal-level types we mentioned before? Instrument level on average falls below line-level so it is safe to plug an acoustic guitar directly into a mixer’s line-level input.
However, you will get a much cleaner and more controllable sound if you use a DI box for an acoustic guitar. It is standard to use one for professional live performances.
Bass guitar
Most bass amplifiers have a DI output, which proves that a DI box (in this case – integrated), is what a bass guitar needs to send a clear and unaltered tone to the mixer. Again, it is possible to plug a bass guitar into a mixer’s line input.
Venues with bad wiring
Some venues just have bad wiring, it’s a fact. When playing in those venues you never can’t be sure that there will not be any hum picked up from your instrument cables. With a DI box, we can easily avoid this problem.
Backup solution
Every guitarist should have at least a small DI box in case their amp doesn’t work. It will save you! Instead of plugging into your amp, plug your guitar into the DI box and send the XLR output to the soundboard. I have experienced at least three situations where my amp didn’t work, and the Mooer Micro DI saved the show. Two times. The first time it happened I had no DI box, awful experience. My guitar’s sound had no life in it, no high-end, just the sound of some distant strings being played.
Specialized DI boxes
Split signal
Some guitar and even bass rigs use this method. Di boxes that have two outputs, one TS jack output for the amp (microphone in front) and one balanced XLR for FOH are used. These two signals are then blended for FOH.
DI box preamplifier
This type of DI box is for those who want additional features that can be controlled during performances. Besides being a DI box and preamp they can have any of these features:
- Footswitches for boosting, muting, A/B instrument switching, or ON/OFF for FX loops and tuning
- Anti feedback
- High-quality EQ
- Tuner outputs
- Blending multiple instruments,…
Speaker simulation DI box
This type of DI box is used when we want to capture the characteristic sound of an amp without the use of a microphone. It can only be used if we have a separate amp and speaker cabinet or if the amp has special “amp out” and “speaker in” plugs. The guitar is connected to the amp input. Instead of connecting the amp to the speaker, we connect the amp’s output to the DI box’s input. These DI boxes have two outputs: one goes to the speaker using a speaker cable, and the other is an XLR-balanced output that goes to the mixer.
By using this Di box, we can adjust our guitar’s volume and EQ on stage without affecting the signal sent to the FOH. Besides capturing the amp’s tonal characteristics this method benefits from zero feedback issues because there is no microphone involved.
Reamping
This is something that is used for studio purposes, not live. The whole thing works the opposite way than with classic DI box usage.
The goal is to use the amp for recording purposes AFTER the guitar is recorded with a DI box.
- The guitar goes to a DI box and then to recording gear, usually an audio interface. We record a clean sound with no effects or amp.
- Now the recording is sent to a special Reamp DI box that is fed to an amp.
- We can now experiment with different amps until we achieve a desired tone without someone playing the guitar every time we make changes to amps and effects.
Passive vs active DI boxes
Palmer’s site explains it like this:
When is a DI box not needed?
If you prefer the unique sound that you are getting from your tube amp and awesome pedals and don’t need special routing, the microphone in front of your amp will do all the work for the main soundboard. This is the way to go in small venues where the cable runs are short.
For small gigs, bass and acoustic guitars can get away without using a DI box, especially when someone forgets to bring their DI box 🙂.
Di box in the signal chain
If you are using a dedicated DI box for your guitar rig it should be placed right after your pedals. After that, the signal goes to the mixer. If you have a DI box with two outputs, the other output can be used for your personal monitoring via a classic guitar amp or an FRFR speaker.
Conclusion
A DI box is a very important piece of professional musical gear. It will make your guitar sound the best it can show after show. By converting the signal to a low-impedance balanced signal that is suitable for mixers it eliminates signal loss and interferences.
Acoustic guitar players, bassists, and electric guitar players with an ampless rig will benefit the most from using a DI box. Also, whenever there is a longer cable run, a DI box is crucial for maintaining clean and uncolored sound. And let’s not forget how valuable they are when special signal routing is needed. Don’t forget to have at least a mini DI box in case your guitar amp doesn’t work!
No matter why you use a DI box, it will provide your instrument with a stable, uncolored, and professional sound wherever you play a gig.
