Acoustic Amp Modeler / DI Box The ADI21 combines the features of an active DI box with proprietary microphone/tube emulation. If you don't want to use the emulation feature, the ADI21 also functions as a superb active DI box. The BLEND control allows you to mix the amount of modeled tone with your instrument's normal output. The resulting sound is more natural with smooth saturation, just as if your guitar were being mic'd.