The magical and essential DI box gets you from stage to board. How does it work?
Have you used DIs from time to time?
- Sure! I used to keep a D/I box when my rig didn’t have a D/I built in. Specifically for gigs with PA’s that I wanted to run through (Behringer).
- Also use a Tech21 DI preamp for quick studio stuff
- So my PA box has a handful of DIs, mainly the standard Whirlwind but I think I have a Behringer and something else in there.
- Used a wonderful Avalon U5 once at a studio, lustworthy but VERY expensive
- Like Dave, my rigs usually have a built-in DI nowadays
What does a DI do?
- Turns an unbalanced signal into a balanced one.
- What’s unbalanced? A line with only two connections: ground and signal. Examples include tip-sleeve (TS), or RCA.
- Balanced has three connections: ground, live, and return. Examples include XLR cables (three pins!), or tip-ring-sleeve (TRS). Note the TRS for your phone/iPod isn’t balanced, but looks like it at the end that plugs into your phone.
- Balanced lets you reject more noise and interference, because basically the live and return get the same interference, so with one of them being inverted at the source, you get the noise canceled out and are left with signal.
When do we use it?
- Trying to elevate an instrument level signal to go into a mixing board
- Examples: some keyboards/synths, acoustic guitar pickup
- Run a very long way to a mixing board
- You won’t find 150-foot instrument cables, but you can find long XLR cables
Passive vs. active
- Active = powered (battery or wall, or phantom power sometimes)
- The expensive DIs are usually active and can function basically as a pre-amp
- No batteries needed, but limited in that they can’t raise a very low level signal high enough
- May not work for certain instruments or pickups
- But cheaper
Pre and post DI switch on your amp
- Pre means the DI sends your signal before your EQ or effects — just the “pure” signal
- Post means the DI sends your signal after all the EQ/FX
- If you have a dedicated sound man or crew who handles all the processing, you probably want pre — otherwise post!
- For example, most of us have to tune our own instruments on stage… so you want your tuner or mute to also mute the PA → Post setting!
Any stupid DI tricks?
- Some modeling gear may have DI functionality, like a balanced direct signal
- Some DIs are oriented toward certain instruments
- Radial Tonebone for bass, but they have a model that has two inputs, and one’s matched for upright pickups so if you double on a gig, you’re set
- Some passive DIs let you connect them to revert a line level signal down to instrument level, so you can take a recorded direct track and run it through different amps
- Nowadays, though, lots of folks will use amp simulators and just do this in the box (meaning entirely on the computer with plugins)