Direct Boxes, often referred to as a DI (which stands for “direct injection”), exist to convert high impedance signals from instruments into low-impedance signals that can be run over distance to a console or other destination. A direct box is a common need for guitars and keyboards but is also generally used for an instrument that has a pickup in it. High impedance signals generally lose their sonic integrity over distance, so converting it to a low-impedance signal will generally improve its sound over 15-20’ of distance. Additionally, a DI will convert an unbalanced signal to a balanced signal, the preferred input for most audio consoles.
A DI also isolates electronic equipment on stage from the audio console, which can help eliminate interference and noise caused by ground loops or other electrical interactions. Most audio engineers have run into some occasion where a guitar channel was producing a significant hum, the ground lift switch on a good DI helps the show go on in those cases. Additionally, it also blocks phantom power sent from the mixer so it cannot interact with the instrument or device connected to the DI's input.
Active vs. Passive DI Boxes
There are two main types of direct boxes. Passive DIs are typically low-cost and very durable, making them quite popular. Furthermore, they work well with instruments with strong outputs. The main benefit of an active DI is that they include a preamp. This allows you to increase the input's gain, which helps with a weak input or for long cables. Additionally, many active DIs have more settings, allowing you to fine-tune or color the sound. These can include advanced signal routing and higher headroom, which is excellent for keyboard instruments. They also require external or phantom power, and typically cost more than passive DI’s.
Additional Direct Box Features
Though you can still find plenty of DIs with just the bare necessities, there are lots of extra options you can choose from.
Single-channel DIs are the most common version of DI available, but many multi-channel DI’s exist. They are perfect for keyboards, computer setups, and typically have between 2-8 channels.
Thru (short for "throughput") and bypass outputs split the input signal into two. Typically, one of the signals is used for onstage amplification and remains unprocessed. This can allow a clean feed to go to the audio console for mixing into the house mix while still allowing for a local feed to connect to an amplifier on stage.
Though DIs do an excellent job of reducing background noise by converting unbalanced signals to balanced ones, there can still be a buzz from ground loops. DIs with ground lift allow you to shield the preamp to eliminate the noise.
The Pad feature allows you to reduce excess gain overload when an instrument produces too much signal. The DI circuit reduces gain by a fixed amount (usually -15 dB), to bring that input down to a usable level.
At times you may have multiple inputs for an instrument or may have multiple microphones picking up a single source. When those signals have closely matched polarity, you can have a decrease in output. Reversing the polarity of one of those sources will reinforce each other, allowing for a full-strength signal.
CCI Solutions has a wide selection of direct boxes for you to choose from. With popular brands like Radial, Countryman, Radial, Behringer, and DBX, we have the perfect audio and sound equipment for your needs.