The XQP 531A Optical De-esser is the newly designed upgrade to the 531 optical de-esser, which was the original 500-series version of the Dane #31, developed in the mid-90's. Selectable VACTROL or Silonex opto-isolators (Soft and Clean modes) provide sibilance reduction in either the classic style or the more subtle, cleaner style.
The side chain now adds a fourth, lower frequency (W) to the improved high pass filters for isolating sibilant content. This HPF design allows the user to select the bottom of the frequency range of potential sibilance resulting in any sibilant above that point being affected.
Design changes of the 531A also include the new, smaller knobs in a revised color scheme, illuminated In switch, and removable stainless side panel for easier servicing.