Behringer FBQ1000 Manual - Page 4

4 FEEDBACK DESTROYER FBQ1000 User Manual 1. Introduction 1.1 The design concept The philosophy behind BEHRINGER products guarantees a no-compromise circuit design and employs the best choice of components. A 24-bit DSP is used as the heart of the FEEDBACK DESTROYER, which belongs to the best components available owing to its outstanding specifications and excellent sonic characteristics. What is more, high-quality 24-bit A/D and D/A converters ensure the accurate processing of all signals. Additionally, the FEEDBACK DESTROYER uses high-quality resistors and capacitors with very tight tolerances, high-grade switches, and further selected components. The FEEDBACK DESTROYER employs SMD technology (Surface Mounted Device). These subminiature components known from aerospace technology allow for an extreme packing density and improve the unit's reliability even further. Additionally, the FBQ1000 was manufactured in compliance with an ISO9000 certified management system. 1.3 Background: How is feedback produced? A feedback loop is produced when a microphone signal is reproduced by an amplification system and is subsequently picked up again (with identical phase) by the microphone. If this happens repeatedly, such a feedback loop can become ever more persistent. 1.2 Before you begin Your FEEDBACK DESTROYER was carefully packed in the factory and the packaging was designed to protect the unit from rough handling. Nevertheless, we recommend that you carefully examine the packaging and its contents for any signs of physical damage, which may have occurred in transit. ◊ If the unit is damaged, please do not return it to us, but notify your dealer and the shipping company immediately, otherwise claims for damage or replacement may not be granted. Shipping claims must be made by the consignee. The BEHRINGER FEEDBACK DESTROYER requires one standard 19" unit of rack space. Please allow at least an additional 4" depth for the connectors on the back panel. Be sure that there is enough space around the unit for cooling and please do not place the FEEDBACK DESTROYER on high-temperature devices such as power amplifiers, etc. to avoid overheating. ◊ Before you connect your FEEDBACK DESTROYER to the mains, please make sure that your local voltage matches the voltage required by the unit: The fuse holder on the female mains connector has 3 triangular markings, with two of these triangles opposing each other. The FEEDBACK DESTROYER is set to the operating voltage printed next to these markers and can be set to another voltage by turning the fuse holder by 180°. CAUTION: This instruction does not apply to export models exclusively designed, e.g. for 115-V operation! Please use the enclosed power cord to connect the unit to the mains. The cord complies with all applicable safety standards. ◊ Please note that all units must be grounded properly. For your own safety, you should never remove any ground connectors from electrical devices or power cords or render them inoperative. Fig. 1.1: How a feedback loop is produced 1.3.1 Background: front of house mix (FOH) There are two main sections in any sound reinforcement system, which are liable to produce feedback: the first section is the so-called front of house mix (FOH), i.e. the "public address" mix, which is reproduced by one or several amplifiers plus several loudspeakers directed at the audience. 1.3.2 Background: monitor mix The monitor mix, which is often derived from the same console, feeds one or several stage-mount monitor speakers. Unlike FOH systems, stage monitors are used to provide the individual musicians with a monitor signal, because it is often difficult to hear oneself or each other on the stage, which can be due to the high volume levels produced by the FOH systems, or to different volume levels of the stage-mount instruments and amplifiers. It is therefore not unusual to give each musician his or her own monitor speaker, which is why there are usually several monitor speakers placed along the stage. This is the only way to provide each musician with a directed and focused monitor signal. In an ideal situation, each monitor provides a specific mix, comprising e.g. vocals, drums and keyboards, for each individual musician on the stage. Unfortunately, it is anything but easy to find perfect positions for the various stage monitors, because the distance between speaker and microphone must be kept very short, which in turn increases the risk of feedback. ◊ In contrast to FOH systems, it is common practice to create two or even more dedicated monitor mixes, which also involves the use of several monitor speakers. Again, this can lead to increased feedback. As a standard, the BEHRINGER FEEDBACK DESTROYER is equipped with electronically servo-balanced inputs and outputs. The circuit design features automatic hum and noise reduction for balanced signals and thus allows for trouble-free operation, even at high operating levels. Externally induced mains hum, etc. will be effectively suppressed. The automatic servo-function recognizes the presence of unbalanced connectors and adjusts the nominal level internally to avoid level differences between the input and output signals (6-dB correction). The MIDI interfaces IN, OUT, and THRU are on standardized DIN connectors. Data are transmitted via potential-free opto couplers.