The Orban 526A Dynamic Sibilance Controller has been designed as a universal de-esser for the recording, broadcast, and motion picture industries. It offers electrical specifications consistent with other state-of-the-art audio signal processing equipment, extremely simple setup and operation, and dynamic characteristics which have teen optimized for sibilance control. The 526A incorporates a circuit which forces the threshold of de-essing to track the average input level, permitting constant amounts of de-essing and audibly consistent results over an input level range of approximately 15dB. Compared to its widely accepted predecessor, the three-channel 516EC, the 526A offers the following improved features: 1) transformer-coupled, balanced inputs and outputs; 2) mic and line-level inputs; 3) five-segment peak-reading output level indicator; 4) gain control; 5) two segment (normal and heavy) gain reduction indicator; 6) full RFI suppression; 7) improved circuit stability; 8) improved control-loop dynamics; 9]higher slewrate and lower high-frequency distortion. De-essers have existed for years, usually as frequency-dependent sidechains in limiters or compressors. However, a compressor used as a de-esser cannot function optimally if one attempts to compress and de-ess with the same device, since optimum compression ratios, attack times, and release times are quite different for the tv modes of operation. In addition, such devices are often insufficiently adjustable, and often contain simple filters whose selectivity is inadequate to provide sufficient differentiation between sibilance frequencies and the lower frequencies where most of the voice energy is concentrated. Further, these devices cannot simultaneously de-ess voice and maintain natural dynamic range because their thresholds are fixed. It is clear that a specialized de-esser is therefore necessary to perform the sibilance control only. It is ordinarily the last piece of processing hardware in a chain which may include both an equalizer and a compressor or limiter. Both devices will tend to increase sibilance with reference to the energy of the lower-frequency vocal components; the de-esser then knocks down sibilance levels until they are once again natural-sounding and do not cause overload in recording media employing high frequency preemphasis. It is this function which the 526A serves. When not de-essing, it acts as a high-quality amplifier. When the level in the sibilance band attempts to exceed a certain fraction of the peak input level (said fraction being adjusted by the operator with the threshold control) , then the gain is automatically reduced to hold the output at this threshold level. Hie 526A attacks in approximately 1mS and recovers in approximately 1OmS. It can thus act on sibilance without affecting surrounding vocal sounds. Because the entire channel gain is reduced (as opposed to de-essers which operate as program-controlled filters) , any residual IM distortion which accompanies the original sibilance is reduced along with the sibilance itself.