This post focuses on the topic of using direct injection/input to bring clarity to traditionally recorded tracks.
When you were first starting out in the world of audio, you probably tried something along the lines of plugging a guitar or bass directly into your audio interface or mixer. I know I did this and learned very quickly that the tone that results is less than stellar or interesting. It’s extremely dry, lacks harmonic content, and sounds brittle. But, in the right situations, these very same qualities can be a godsend when blended with a regularly amped sound. Hence we end up with the technique of blending DI sounds with their amped counterparts, which is most commonly used with electric bass.
What Amped Sounds Bring to the Table
The sound of a bass amplifier that is correctly miked is large, round, and has a pleasing thump to it. It gives the bass a sense of space that helps it sit nicely in the mix. Effects such as distortion are mellowed by the amp and given character by the speaker cabinet. But, often this sound just is too thuddy to be heard cleanly (listen to many of the bass parts in the late sixties and early 70s for examples… they’re downright farty.)
What DI Sounds Bring to the Table
DI sounds are clear and pristine. They have 100% of the transient response of the instrument, unencumbered by the need to move a speaker coil and, then, to move the air towards the microphone and, then, move the microphone’s diaphragm. All of that movement takes time and is what imparts the mellow sound of the amp. You get none of that with DI and the bass response, as a result, is incredibly clean.
Try splitting the bass signal while tracking, sending one split to the amp and the other to the DI. Then, on the mixer, throw them on separate tracks. Bring up the amped sound to full and gradually increase the DI sound until you hear the attack of instrument improve. If the sound starts to get too rubbery or brittle, you’ve gone too far. Next, EQ the two sounds to compliment each other. If you require more clarity in the low end, EQ out some mid lows from the amped track and hi/low pass the DI to fit in. If you require more clarity in the fretting, scoop out a bit of midrange from the amp and, again, dial up the DI to fill in the gap. This is particularly helpful if the amp has distortion on it. Leaving the DI signal clean will allow you to capture all the low end of the bass while leaving the amp to produce gutsy high and mid harmonics. This also works for other instruments with pickups. You can’t beat that combination! Compress the result to taste to glue the two together even more.