Instrument output levels span a very wide range from the millivolts up to ~10 volts. In the following sections we’ll see how this simple component can do so many things by showing how it solves the three problems we identified above. These wires are called the primary and secondary windings. That is, an alternating current (which in this case carries audio signal) in the first wire generates a magnetic field in the core, which in turn generates a corresponding current in the second wire. The wires themselves do not touch each other, yet signal transfers between them through the principle of electro-magnetism. A transformer is a large, primitive analog component that ought to be obsolete except for the fact that it can do several things at once all while sounding great.Ī transformer’s construction is very simple: it’s a single magnet with two wires wrapped around a metal core.
What makes passive DI boxes so elegant and simple is that they utilize a single component to solve all these problems: a transformer. In most cases the differences aren’t so obvious, but they’re just as real. If you plug your guitar directly into the wall, the guitar will be hit with 120v mains power and something will explode or melt. In the case above the answer is obvious: voltage. The most obvious and dangerous example of this is shown below.īut why not? Incompatibilities come down to three main things: One of the first things you learn (very often the hard way) is you can’t just plug anything anywhere. The ProblemsĭI boxes were created to solve a particular set of problems that arise when connecting instruments to pro-audio equipment. Passive DIs, the kind we’re talking about here, require no power and feature only a couple passive components. Active DIs run on DC power, usually from the +48v phantom power from the preamp connected to the output, because they feature active components like transistors and integrated circuits. There are two types of DI boxes: active and passive. The most common scenarios for this are plugging bass and keyboards into the mixing board for live sound, or recording bass and guitar through mic preamps in the studio.
But what, exactly, do these little boxes do and why do we need them? In other words, why can’t you plug a guitar right into a mixing board or audio interface? DI BasicsĪ direct input box is used when we want to connect an unbalanced, instrument output to a balanced, microphone preamp input. If you’ve spent even a little bit of time in a recording studio or doing live sound, you’ve undoubtedly worked with a DI box.
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