Audio Authority 1184 Active Signal Hum Eliminator / DC Blocker
Designed to solve the problem of rolling video hum bars caused by AC-line related noise due to ground loops in coaxial cabling. The 1184 also eliminates hum from low level stereo audio signals. Television displays and projectors usually have a hard connection between their inputs and chassis. Therefore, a ground loop may develop, leading to 60Hz current flowing in the input cable, which causes hum bars. Model 1184 uses active circuitry to isolate the input and output grounds. It also includes video input clamping to thoroughly eliminate artifacts caused by differences in electrical potential between the chassis of equipment connected to it. Passive devices, known as hum buckers or video transformers, can be effective in eliminating the effect of the difference in ground potential. The advantage of the 1184 is that its bandwidth is not limited by inductance, as is the case with the chokes used in hum buckers or transformers. Furthermore, as passive devices, humbuckers and transformers are inherently lossy-their gain is a little less than one-compared to the 1184, which has a gain of exactly one. Model 1184 is designed to overcome hum bars on a Component display at the end of a long run of coaxial cable. In these cases, breaking the ground loop is best accomplished at the video input of an offending TV, projector, or video display. This situation could occur in a residence, but is more likely to occur in larger venues, such as clubs and churches. For example, if four component video displays are fed by a component video distribution amplifier and ground current happens to circulate between any of the displays and/or their source, hum bars will appear on one or more of the displays. A Model 1184 can be added at the input of the offending display(s) to break the ground current path and eliminate the hum bars without sacrificing bandwidth or image quality.