Most active DI units provide switches to enhance their versatility.

If the signal is to be connected to a single input then a mixing facility is required in the DI unit.

A passive DI unit typically consists of an audio transformer used as a balun.

An active DI unit contains a preamplifier.

Active DI units can therefore provide gain, and are inherently more complex and versatile than passive units.

Unbalanced signals can be converted to balanced signals by the use of a balun, often through a DI unit.

Less commonly, a passive DI unit may consist of a resistive load, with or without capacitor coupling.

Some instrument amplifiers contain built-in DI units, and can be connected to a mixing console directly without needing an external direct box.

The cheaper passive DI units are more susceptible to hum, and passive units tend to be less versatile than active.

However, this also increases the pickup's output resistance/impedance, which can affect high frequencies if the pickup is not isolated by a buffer amplifier or a DI unit.

Illsley's bass amplifier was recorded inside a small vocal booth with a Neumann FET 47 and a DI unit.

The device on the left would normally be used to connect a high impedance source, such as a guitar, into a balanced microphone input, serving as a passive DI unit.

Active DI units require a power source, which is normally provided by batteries or a standard AC outlet connection, and may contain the option for phantom power use.

For Saadiq's bass, they used a DI unit to connect a microphone preamplifier, increased the gain on a plug-in for less compression, and adjusted the low-end tones with an equalizer plug-in.

To develop basslines for songs, Flying Lotus had Thundercat's bass plugged into a DI unit of a FireWire interface as he improvised riffs to Flying Lotus' suggestions.

A pass-through connector is a second jack, sometimes simply paralleled to the input connector, that delivers the input signal unchanged, to allow the DI unit to be inserted into a signal path without interrupting it.

This is often achieved by connecting the guitar into a DI unit (a Direct Input or Direct Inject buffer box) that is fed to a recording console or, alternatively, bypassing the console by using an outboard preamplifier.

Beginning in 2002, Lee dispensed with using a single bass guitar amplifier in favor of a chain of amplifiers and DI units, which allow the bass guitar to be connected directly to the stage and front-of-house mixers without involving microphones.

There are a variety of hardware options for recording through the headphone input jack, including using iPhone specific DI units like the IK Multimedia iRig, Peavey AmpKit LiNK and the PRS Guitar Bud.

Main writes that DI unit inputs (as opposed to microphone inputs) do not need high-pass filtering as they are not subject to modulation by low-frequency stage wash-low frequency sounds coming from the subwoofers or the public address system and wrapping around to the stage.