Operating Manual for Digital Sound Processor (DSP) V3.0
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The feedback inhibition module has the following adjustable parameters:
Panic Threshold: According to this parameter, "any level higher than the threshold is absolutely a
feedback". When a signal level is higher than the feedback threshold, any of the following
circumstances will occur: a) the output gain is temporarily attenuated to control the speed of
feedback; b) the output level is restricted to prevent out of control; c) the filter's sensitivity is increased
for faster detection and feedback. Once the output level is lower than the threshold, the gain will be
recovered, and the sensitivity is restored to normal state. This value refers to the peak value of digital
range signal. If the value is set as 0, this function is disenabled.
Feedback Threshold: According to this parameter, "any level lower than the threshold is absolutely
not a feedback". This may prevent the module detects feedback in a soft music or due to the noise
of low level.
Filter Depth: It refers to the maximum attenuation of a single filter. A shallow setting may prevent
too much damage caused by the filter or notching filter to the signal. It may cause worse feedback
control, especially in a large narrow resonance system.
Bandwidth: 1/10 and 1/5Oct can be chosen. A constant Q value is adopted. The filter will not
become wider due to the increase of depth. It is recommended to use the filter in the phonetic
environment. In the case of frequent feedback, the bandwidth is set at 1/5Oct because it has wider
bandwidth and greater influence.
Preset: There are four built-in presets: "big music room", "small music room", "big voice room"
and "small voice room". These four presets apply to the default settings of most applications.
Notching Filter's Auto Mode: Auto mode is set for the notching filter. After eight filters are used
up, a new feedback is detected, and the module will check "auto" filter and use it to inhibit new
feedback. Each notching filter has three modes: auto, manual and fixed modes. When Manual mode
is set for the filter, the gain can also be manually set. When Fixed mode is set, the filter always works
and will not be occupied by new feedback points; it still works when being rebooted. If you need to
save these feedback parameters, please click to save the preset button.
Clear: Click the button to instantly clear up all filters. It will clear up all feedback points detected
with inhibition previously. This operation is generally done when recommissioning the feedback
module.
Feedback inhibitor can be used as a tool during the system commissioning to identify feedback
points or as a preventive measure during normal operations. If you want to get higher system
transmission gain and feedback inhibition effect, it is recommended that you debug by following the
steps below:
(a) Reduce the system gain, and use the button "Clear" to reset all filter parameters
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