The DerrEsser EL-DS PLUS from Empirical Labs is a horizontal multi-function dynamic filtering device preinstalled in the EL500 rack. In its basic DS mode, it is an effective, level-insensitive de-esser, a device that will adjust the high-frequency gain on overly treble-y or spiky vocals or other sources in an extremely musical manner. However, unlike other de-essers, the device allows for multiple uses of its circuitry. As a de-esser in the DS mode (HF Limit OFF), the threshold can be set to tame harsh S's (sibilants) that result from an overly bright singer or from EQ'ing to make a vocal sound aggressive and clear. The DS threshold is not level dependant, and compares the amount of high-frequency content to the low-frequency content, so adjusting the overall level does not affect the threshold. It features VCA technology for glitch-free, distortion-free, and noise-free performance. The corner frequency is user adjustable with a high-performance active crossover.
In HF Limit mode, the DerrEsser essentially acts as a high-frequency compressor. If there is enough high-frequency content to exceed the threshold, then gain reduction occurs. It is level sensitive, but responds much more to high frequencies. This mode is more of a general high-frequency smoothing device. In high-pass mode and while using the LISTEN function, the user can employ the filter circuitry inside the DerrEsser to process their audio. With the LISTEN button in, and the HP/LP switch out, the user will be hearing the high frequencies that are being controlled with the dynamic/compression circuits. The corner frequency is adjustable with the frequency knob. In low-pass mode and with the LISTEN button in, and the HP/LP button in, the user is now listening to the low frequencies, those not affected by the VCA and dynamic/compression circuits. This is a 12 dB-per-octave filter whose corner frequency can again be adjusted with the frequency knob.
The EL500 rack features a quiet power supply and offers both XLR and phone rear-panel inputs and outputs. In addition, a 1/4" instrument preamp/direct box input is provided on the front panel, which will automatically switch the left 500 module's input to this front phone jack once something is plugged into it. Switches to link compressors and engage a 48V phantom supply are also provided.