Feedback Eliminator (Afs) - dbx DriveRack 260 User Manual

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DriveRack
Section 4
Detailed Parameters
Slope 9 3-12dB/Octave
Sets the slope of the high shelf parametric EQ.
Level 9 -12 to 12 dB
Sets the overall gain of the high shelf parametric
4.2 Feedback Eliminator
The 260 DriveRack offers the exclusive patent pending AFS (Advanced Feedback Suppression)
feedback elimination module. Feedback is caused when a microphonic signal such as a guitar
pickup or microphone is reproduced by an amplification and is repeatedly picked up in phase.
The AFS uses Precision Frequency Detection and state-of-the-art processing to determine the
exact portions of a given frequency of your feedback that need to be removed (instead of tak-
ing out large sections of your sound). The AFS module of the 260 DriveRack allows the user to
optimize the elimination of feedback. In the past, graphic equalizers were used to eliminate
feedback from a system. This was an acceptable method for eliminating feedback, but when
this method was precision tested, the result clearly showed that a single 1/3 octave EQ slider
was removing approximately half of the signal power. With the AFS, the module removes the
feedback automatically and the proprietary, precision AFS filters remove only a fraction of the
frequency spectrum. The following diagram shows AFS as opposed to competing, competitive
feedback eliminators and conventional graphic EQs:
AFS On/Off
Turns the AFS module on and off. If AFS is Off, the filters are bypassed, and the algorithm is
halted (the filters are not updated). If AFS is On, the filters are active, and the they are updat-
ed according to the current selected mode (Fixed or Live).
Clear Live/All
This parameter clears the filters. If Clear Live is selected, then (if invoked) the live filters are
reset. If Clear All is selected, then (if invoked) all of the filters are reset. When either Clear
Live or Clear All is selected, the third parameter row displays "Start w/ Data Wheel." If Clear
(none) is selected, then nothing is displayed on this row. When the user moves to this third
row and turns the Data Wheel (when Clear Live or Clear All is selected) then the filter reset is
invoked.
Mode - Live or Fixed
When the mode is Fixed, the algorithm updates only the fixed filters. When the mode is Live,
the algorithm updates only the live filters. In FIXED mode, the filters are automatically assigned
to a frequency creating feedback, are stored remain with the program and at that frequency
until cleared by the user. Fixed mode is used before the performance without any input sig-
nal. In LIVE mode, the live filters automatically detect and remove feedback during the per-
formance. When all of the live filters have been used, they begin to round robin. Essentially
this means that the first filter set
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