1. INTRODUCTION
Whether you are on the stage or in the studio, you often find that you need to connect an audio source to your mixing console, but you don’t have the appropriate connectors. For example, only few keyboards feature balanced outputs; guitars should not be connected directly to the console; and placing a microphone in front of an amp is not always an ideal solution, because the mic will pick up unwanted signals from other instruments, too. Low frequency signals (e.g. produced by a bass guitar) are particularly difficult to handle using these techniques.
"DI" is short for "Direct Injection". A Direct Inject box allows you to use a high-impedance, unbalanced source, e.g. the signal between guitar and guitar amp, and feed it directly into an input channel on your console, without having to use a microphone. And that's far from being all. There are plenty of situations in which you'd like to input unbalanced source signals into your console, and possibly convert them to balanced signals before. As you can expect, the DI4000 offers you a reliable solution.
The following explanations will give you an introduction to the complex performance-impedance issue: imped- ance is defined as the dependence of a device's electrical resistance and phase response on the frequency processed. Thus, impedance is one of the criteria that distinguish good DI boxes from poor ones. Much like in a power amp and its connected speakers, impedance determines the performance of the device. With a good power amp, the load impedance will have little influence on the maximum output power, but it can considerably affect other properties. With a passive DI box, the connected load impedances (ins and outs) alter the bandwidth, frequency response, distortion, etc. of the DI box.
By the way: there are two basic types of DI boxes, passive and active. Both can be connected to one of the console's mic inputs. Passive DI boxes offer the advantage that they are less expensive than active models (less electronics, no power supply), however, their performance depends on the connected impedance. With a passive DI box connected, any impedance change on the console side will also modify the input imped- ance. The frequency response will always depend on the impedances connected. Any passive DI box will only perform properly with accurately specified impedances (high on the input side, low at the output), i.e. it will only work in standard situations.
Active DI boxes such as our ULTRA-DI PRO, however, do not suffer from such restrictions, because they use an amplifier circuit to buffer the input signal. Since the ULTRA-DI PRO's input impedance is ultra-high, the signal remains unaffected as it passes through the DI box. Additionally, the ULTRA-DI PRO features bal- anced impedances on the output side, making the signal less susceptible to hum and noise interference. In this way, the signal as source impedance is completely independent of the console used (and vice versa), which means that the sound remains totally unaffected. The ULTRA-DI PRO uses our proven OT-1 trans- former which ensures a clear and distortion-free sound and linear frequency response. Additionally, the ULTRA-DI PRO comes with a built-in power supply.
Future-oriented BEHRINGER technology
The ULTRA-DI PRO is based on SMD technology (Surface Mounted Devices). These subminiature compo- nents known from aerospace applications ensure both extreme packing density and greater reliability.
High-quality components and design
The philosophy behind BEHRINGER products guarantees a no-compromise circuit design and employs the best choice of components. The op-amps, type 4580, used in the ULTRA-DI PRO are chosen for their superior signal-to-noise ratio, low distortion and linear performance. Additionally, the ULTRA-DI PRO uses high quality resistors and capacitors with very tight tolerances, high-grade switches as well as other selected components.
