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DI Boxes & Signal Processors

Our range of DI boxes and signal processors covers the small units that solve real problems on stage and in the rack, from getting a keyboard cleanly into a mixer to killing the hum on a long cable run. We also stock audio interfaces for recording and power conditioners for protecting a rack. Found it cheaper elsewhere? We will match the price.

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What a DI box does

A DI, or direct injection box, takes an unbalanced instrument level signal and converts it to a balanced microphone level output that can travel down a long XLR cable without picking up noise. That is what lets a bass, keyboard or acoustic guitar plug into a stage box thirty metres from the mixer and still arrive clean. Most also provide a through output so the same signal still reaches the player amplifier on stage.

Active or passive?

A passive DI uses a transformer, needs no power and handles high signal levels well, which makes it the reliable choice for basses with active pickups, keyboards and line level sources. An active DI needs phantom power or a battery and provides a higher input impedance, which suits passive pickups on electric and acoustic guitars, preserving the top end that a passive box can soften. If you only buy one, a passive box is the more foolproof, but a guitarist with piezo pickups will hear the difference an active makes.

Audio interfaces for recording

An interface is the bridge between microphones or instruments and a computer, providing preamps, phantom power and conversion in one box. Count the inputs you need to record simultaneously rather than in total, since two inputs is plenty for a vocal and a guitar but a drum kit needs far more. Check that it offers a headphone output with its own level, because monitoring through the computer introduces enough delay to make overdubbing difficult.

Power conditioning and rack protection

A power conditioner distributes mains across a rack, filters some of the noise that sits on a supply and gives surge protection to everything plugged into it. In a venue with dimmers or motors on the same circuit, that filtering is audible. Look for a unit with the outlet count you need at the rear, and a front panel switch if you want the rack powered up in one action rather than device by device.

Ground loops and hum

Hum almost always means two devices are connected by both a signal cable and separate mains earths, creating a loop. The proper fix is a balanced connection, a DI box with a ground lift switch, or an isolating transformer. Never remove an earth pin to solve it, since that is dangerous and does not address the cause. Try the ground lift first, as it resolves the majority of cases without any rewiring.

Frequently Asked Questions

What is a DI box for?
It converts an unbalanced instrument signal to a balanced output that can run down a long XLR cable without picking up noise, which is how a bass or keyboard reaches a mixer thirty metres away cleanly. Most also pass the signal through to the player amplifier.

Active or passive DI box?
Passive uses a transformer, needs no power and handles high levels well, suiting active basses, keyboards and line sources. Active needs phantom power or a battery and offers higher input impedance, which suits passive and piezo pickups on guitars.

How many inputs does an audio interface need?
Count what you record at the same time, not in total. Two inputs cover a vocal and a guitar. A drum kit needs considerably more. Also check for a headphone output with its own level, since monitoring via the computer adds delay.

Do I need a power conditioner?
It is worth having in any rack, and audibly so in venues with dimmers or motors on the same supply. It distributes mains, filters some supply noise and gives surge protection, and a front switch lets you power the whole rack in one action.

How do I get rid of hum?
It is usually a ground loop, where two devices share both a signal cable and separate mains earths. Use a balanced connection, a DI box with a ground lift, or an isolating transformer. Never remove an earth pin, which is dangerous and does not fix the cause.

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