The BDI21 combines the features of an active DI (direct injection) box with our proprietary tube emulation circuitry. It’s like having a truckload of vintage tube amps right at your toes! The Blend control allows you to mix the amount of tube emulation you want with your direct bass signal. And if you just want your instruments straight, pure tone – just step on the switch and the ADI21 functions as a superb active DI box.