Behringer ULTRA-DI DI100 Manual - Page 9

9 ULTRA-DI DI100 User Manual Welcome to BEHRINGER! DI stands for Direct Injection. On stage or in the studio there are sources you want to connect to your mixer that are not equipped with a suitable connection. Keyboards seldom have properly balanced outputs. Guitars cannot be directly plugged into a mixer and placing a microphone in front of a backline is not always ideal. A microphone picks up ambient noise such as other instruments. Low frequencies (such as from a bass guitar) are especially difficult for a microphone to handle. A DI-box makes it possible to tap a signal from a high impedance unbalanced line, for instance the signal from a guitar to a guitar amplifier, and inject it directly into the mixer's input without having to use a microphone. But that's not all, there are lots of situations where you want to inject the signal coming from an unbalanced source directly into your mixer and preferably balanced, too. That is the application of a Direct Injection box. Impedance is the electrical frequency dependent resistance of a device combined with its phase response. It is a literally complex matter. That is why a good DI-box is distinguishable from a bad one. As with a power amplifier and speakers the impedance to a device determines the performance. With a good power amplifier the load impedance only affects the maximum power output. Whereas on some other devices the impedance governs other properties as well. With a transformer as used in a DI-box, the connected impedances (in and out) influence the bandwidth, frequency response, distortion, etc. There are two basic types of DI-boxes, passive and active. Both active and passive DI boxes are designed to be connected to the console's microphone input. A passive DI box has the advantage of being slightly lower in cost (less electronics, no battery facility) but their performance is highly dependent on the connected impedances. When the impedance on the mixer side of a passive DI-box changes, the impedance on the input changes also. Not only that, the frequency response changes, too. A passive DI-box only works well at specified connected impedances, high in and low out, which means that they only work in a standard application. Active DI-boxes don't have such restrictions. The signal coming from the input is buffered with an amplifier. The input impedance of the ULTRA-DI is ultra-high so it doesn't affect the signal throughput at all. The output impedance of the Ultra-DI is balanced and very low so that it is much less susceptible to picking up hum and noise. This way, the impedance for the signal source is independent from the impedance of the used mixer and vice versa. There is no sound alteration. The transformer used is BEHRINGER´s renowned OT-1 witch guarantees distortion free, clean sound and a flat frequency response. Furthermore the BEHRINGER ULTRA-DI can be powered by your console's phantom power or by battery and switches automatically between these two.