A DI box sits between an instrument and the mixing desk. It takes the unbalanced jack signal from a guitar, bass, keyboard or laptop and turns it into a balanced XLR line that can run the length of a hall without picking up hum. We hire both kinds — passive boxes that need no power at all, and active boxes that run from the desk's phantom power — at £2 per day each, dry hire or with a technician. Tell us what is being plugged in and we will send the right ones.
Every input on a mixing desk really wants a balanced signal, and instruments do not give one. A guitar, a keyboard or a laptop headphone socket puts out an unbalanced signal on a jack lead, and unbalanced signals collect hum and buzz as the cable gets longer. A DI box — direct injection — does the conversion. Instrument jack in, balanced XLR out, and the XLR line will run thirty metres to the back of a hall and arrive clean. Most boxes add two useful extras: a link jack that passes the signal straight on to the player's own amplifier, and a ground lift switch that breaks the earth loop behind most steady mains hum.
A passive DI is a transformer in a tough metal box. There is nothing to power and nothing to switch on, which is why it is the default for sources with a healthy output of their own: keyboards, active basses, electronic drum kits, DJ mixers, laptops and backing-track players. For the keyboard in a musical pit or the laptop running a dance show, passive is almost always the answer.
An active DI has a small preamplifier inside, which gives it a far higher input impedance. That matters for instruments with no electronics of their own — a passive electric bass, a guitar plugged straight in from its pickups, an acoustic with a pickup but no onboard preamp. Into a passive box those sources can sound thin and quiet; the active box keeps their level and tone intact. The preamplifier needs power, and it normally takes it as 48V phantom power sent up the XLR by the mixing desk — the same +48V button you would press for a condenser microphone. If your desk has no phantom power, say so when you book and we will supply active units running on fresh batteries instead. Phantom power does a passive box no harm, so a mixed rig on one desk is fine.
There is no rigging and no mains involved. The boxes sit on the stage floor by the player, get plugged in at the soundcheck and are then forgotten about until the get-out. Tell us what is being plugged in, instrument by instrument, and we will make up the right set — stereo pairs for keyboards and playback, actives for the acoustic guitars — with as many boxes as the show needs. If a big band night outgrows what we would normally carry, we bring more in from trusted suppliers.
What you get
The DI box, active or passive as your sources need, tested before it goes out
For active units, 48V phantom power from your desk is assumed; if your desk has none, tell us and we will fit batteries or send battery-capable units
XLR cable from the box to your stage box or desk: let us know the run and we will include the right lengths
Stereo pairs for keyboards, laptops and playback where you tell us the source is stereo
Not included as standard: instrument jack leads, which most players bring, and minijack leads for laptops and phones — both can be added, just ask
Someone to plug it all in and check the lines before the show, if you would rather not do it yourselves
Good for
School musicals where the pit keyboard has to reach a desk at the back of the hall
Laptop and tablet playback for dance shows: a pair of DIs keeps show tracks clean and in stereo
Bass and acoustic guitar in church worship bands and carol services
Battle-of-the-bands nights and school concerts where every act plugs into the same stage box
Village hall events where the mixer is a long cable run from the stage
Am-dram pit bands sharing a few desk channels between keyboards, guitars and click
What you need to know
What it does
Converts the unbalanced jack output of an instrument, keyboard or laptop into a balanced XLR signal that can run a long way to the mixer without collecting hum.
Phantom power
Passive boxes need no power at all. Active boxes run from the 48V phantom power on your mixing desk, or from a battery if your desk has none — tell us which when you book.
Connections
Quarter-inch jack in, a link jack out to the player's own amp, and balanced XLR out to the desk or stage box.
Where it goes
On the stage floor next to the player, or under the keyboard. A small metal box with no mains lead and nothing to rig.
Who runs it
Nobody, once it is plugged in and checked at the soundcheck. If there is hum, flick the ground lift switch; otherwise leave it alone.
Hire rates
Item
Rate
Active DI Box
£2 / day
Passive DI Box
£2 / day
Rates are per day and exclude VAT. Ask us about multi-day and show-week rates, delivery, and hiring with a technician.
Check availability
See whether this is free for your dates. This is an indication from our current bookings, not a reservation.
Full technical specification (8)
Type
DI (direct injection) box — active and passive units available
Input
Unbalanced 6.35mm jack, for instrument or line-level sources
Link output
Second 6.35mm jack passing the input straight on to the player's own amplifier
Output
Balanced XLR at microphone level, into any mixer or stage box
Power, passive units
None — a transformer does the conversion
Power, active units
48V phantom power from the mixing desk, or an internal battery
Switches
Ground lift for curing mains hum; an attenuator pad on most units for very hot sources
Mains
No mains connection at either kind of box
Common questions
The rule of thumb is the opposite of the source. Anything with its own power — a keyboard, laptop, electronic drum kit, DJ mixer or active bass — goes into a passive box. Anything without — a passive electric bass, a guitar straight from its pickups, an acoustic with no onboard preamp — wants an active box. If you are not sure, tell us what is being plugged in and we will send the right one. The price is the same either way.
It is 48 volts the mixing desk sends back up the microphone cable, and it is what powers an active DI. Look for a button marked +48V or P48 on the desk, either per channel or as one global switch; almost every modern mixer has it. Running the active box from phantom means no battery to die mid-show. Passive boxes ignore phantom entirely, so it is safe to leave on across a mixed rig. If your desk has none, we will send battery-powered units instead.
Over a short lead into a spare stereo input, yes. But headphone outputs are unbalanced, so over a long run to the desk they pick up hum, and one minijack carries two channels that the desk wants on two separate inputs. A minijack lead into a pair of DI boxes is the reliable way: clean stereo on two XLR lines, however far away the desk is.
Yes. The box sits between the instrument and the amp: instrument into the input, link jack on to the amp as normal, XLR to the desk. The amp behaves exactly as it always has and the player hears no difference, while the desk gets its own clean feed to mix and balance.
Usually. The balanced XLR line refuses most interference on the way to the desk, and the ground lift switch on the box breaks the earth loop that causes steady mains hum — try it in both positions and keep the quiet one. If the hum survives that, the cause is normally upstream, often lighting dimmers or the instrument itself; tell us the symptoms and we will help you chase it.
