How to DI Guitar or Bass and Boost Your Input Signal in Logic Pro X

When it comes to recording guitar or bass, there are several ways to get the job done. The standard for many decades has been placing a microphone in front of an amplifier, channeling your microphone signal into an audio interface, and then have that signal be recorded onto a tape machine or into a DAW. But for many reasons (maybe you don’t want to bother your neighbors with loud guitars, your amp is broken, or you’re just looking for a different set up) you may want to DI your guitar or bass instead.

DI stands for ‘Direct Input’. When you DI a guitar or bass, you’re sending the raw signal created by your instruments pickups directly into a DAW, bypassing the signal produced by your amplifier and microphone. A benefit to DIing your instrument is that your raw instrument signal is not subject to any interference by outside sources that can be picked up by a microphone or amplifier. This raw signal however will lack any sort of signal manipulation like boosting, distortion, reverb, or other effects created by guitar pedals and your amplifier. This lack of signal manipulation will make your guitar or bass sound thiner and drier, but there are ways to combat those unwanted effects.

DIing in Logic Pro X

To get started DIing your instrument in Logic Pro X , make sure your audio interface is connected to your computer and recognized by Logic Pro X. You can achieve a DI input by plugging a traditional 1/4″ cable (guitar cable) into your instrument and plugging the other end directly into your audio interface. Once your audio interface is properly set, create an audio track with it’s input corresponding to the channel that your instruments output signal is being sent into. If you’re having trouble getting a signal, you may need to check your audio preferences and make sure your input is set to your audio interface.  After doing this, you should begin to get signal. To hear the signal, activate the initiate button (indicated by the ‘I’) on the audio channel.

Once you get signal, you can begin adding different plugins to effect your sound like you normally would but you may notice that your input signal is too low or doesn’t sound as full as you like it to. You can raise the gain on your audio interface channel to get a louder signal but make sure you don’t set it too high or else you’ll clip your audio signal and have unnecessary distortion. Raising the signal gain on your audio interface still may not provide the desired clean tone you’re looking for. To further raise and clean up your guitar or bass signal, you can add a preamp or DI box to the beginning your signal.

Below is a video from MusicTechHelpGuy that demonstrates how to set up a DI channel in your Logic Pro X project along with some other editing techniques.

Preamps and DI Boxes

Preamps are an excellent way to get the robustness of your instruments sound back while using DI on guitar or bass. ‘Preamp’ is short for ‘Pre-amplifier’ and the main purpose of a preamp is to make a weak signal louder by adding gain while reducing unwanted noise. While most audio interfaces are considered preamps, there are designated software plugins and hardware preamps/DI boxes that you can use to boost you signal to get a better guitar or bass tone as your finished product.

Placing a DI box or preamp (physical or digital) at the beginning of your signal chain is crucial to getting the most out of your tone and a high quality sound. A good DI box or preamp will add gain to your signal without all the extra noise, leaving you a signal that is loud and clean. As you begin to add effects to your signal chain you’ll want a strong base signal that your effects and other processors can use to do their jobs properly. Without a DI box or preamp, your input single can be too weak and making it difficult for you to get the desired effect out of your plugins. Specifically in Logic Pro X, there is a DI box plugin that can get you some killer boosted tones.

You can find this DI box emulator located in Logic’s bass amp section of presets titled ‘Clean DI’. This digital DI box emulates a traditional hardware DI box that you might find in a professional sound studio. Very often, bass parts are recorded through a DI box and into an audio interface because it offers a cleaner and less muddy signal. Though this DI box plugin is found in Logic’s bass amp section, it still works great for guitars or any other instrument you’re sending a direct signal from.

As you can see above, this DI box is simple to use, only sporting four main controls. You’ll see a Boost knob, a Tone knob, an HF button, and an on/off button for the tone knob. The boost knob adds gain to your input signal, making it louder and changing the color or saturation of the signal. Engaging the HF button below the boost knob activates a high-pass filter that is meant to reduce unwanted noise made by a rise in gain. The tone knob has six preset EQ curves that you can cycle through to further adjust your tone. The on/off button below the tone knob simply turns the tone control on and off.

If you take a look at the bottom of the plugin interface, you’ll see some extra options to further effect your signal. Logic Pro X comes stock with loads of amp simulators. You can have your DI box run parallel to a digital amp of your choosing by selecting the amp type, cabinet, and adjust the ratio of DI box to amplifier using the blender slider. Using these controls can get you some interesting clean tones and get you closer to sounding like you’re playing out of a real amplifier.

Logic Pro X’s selection of digital amp simulators is very well rounded, offering hundreds of combinations of different amp heads, cabinets, and speakers. You can even choose microphone type and placement which is a great bonus feature and really effects your sound. Using one of these digital amplifiers will get you lots of useful guitar and bass tones as the digital amp head and speaker boosts your input signal just like a regular amplifier does.

Using Your Amplifier as a Preamp

For those who don’t know, a physical guitar and bass amplifiers are composed of two main parts, a preamp and a speaker. When you plug your instrument into your amp and start playing, the signal from your instrument is directed into the preamp (a.k.a. an amp head) which processes the signal with effects like EQ or distortion into a signal that can be projected through the speaker. On many guitar and bass amps there is an output jack located on the back that you can use to bypass your amplifiers speaker and redirect the signal directly into your audio interface. Doing this achieves the same effect as a DI box. This can be helpful if you prefer to use an analog preamp over a digital one.

If you don’t want to use your amplifiers preamp, there are amp simulator pedals that act as miniature amp heads and can be even more versatile than your amp head. Amp simulator pedals often are able to mimic multiple kinds of amplifiers while offering EQ and distortion controls. An excellent example is Behringer’s Tube Amp Modeler. The Tube Amp Modeler has settings to mimic classic amp models from companies like Marshall, Fender, and Vox all in one little pedal. By placing this pedal just before your audio interface in your signal chain, you can get some great sounding guitar tones without using your amplifier.

There are many ways to DI your guitar or bass as long as you understand the principles of your signal flow. You can use many different digital and physical devices like DI boxes, digital amp simulators, physical amp heads, amp modeler pedals, or outboard preamps. Because there are so many options and ways to achieve great guitar and bass tones, it truly comes down to personal preference. Some producers prefer analog devices while others like digital. For whichever reasons you choose to one over the other, Logic Pro X is compatible with almost any set up you choose.

Below is a short video from Sweetwater that further breaks down what a preamp is and why you may want to use one: 

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