The EL-Rx DocDerr and EL-DS DerrEsser Signal Processors with Horizontal EL500 Rack from Empirical Labs combines a multi-purpose tone enhancement module and a multi-function dynamic filtering device; pre-installed in the EL500 rack.
The DocDerr offers six different sections of digitally controlled analog processing. A low-noise preamp capable of working with line level or instrument level signals is followed by four sections of EQ combining a two-position, high-pass filter with three parametric bands, each with its own set of carefully tuned frequency presets. By adjusting an internal jumper, the DocDerr offers a high quality instrument preamp with 16 dB of gain for acoustic guitar, bass, synths, and exotic plucked instruments. The dynamics section offers compression and a musical tape emulation circuit that softens and tames high frequencies and transient spikes. The Mix knob allows the user to blend the uncompressed signal with the compressed and saturated signal. The DocDerr is well suited for tracking, fine-tuning tracks during mixing, and studio-quality tone control.
The DerrEsser is an effective, level insensitive de-esser device that adjusts the high frequency gain on overly trebly or spiky vocals or other sources in an extremely musical manner. However, unlike other de-essers, the device allows for multiple use of its circuitry. In the DS mode (HF Limit OFF), the threshold can be set to tame harsh sibilance that results from an overly bright singer or from EQ'ing to make a vocal sound aggressive and clear. The DS threshold is not level dependent, 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, distortion, and noise-free operation. The corner frequency is user adjustable with a high performance active crossover. The HF Limit mode 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 and functions more of a general high-frequency smoothing device.
The Highpass mode uses a LISTEN function, where 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 controlled by the dynamic/compression circuits. The corner frequency is adjustable by the frequency knob. The Lowpass mode also uses the LISTEN function, but with 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 by the frequency knob.
The EL500 rack features a quiet power supply and offers both XLR and 1/4" rear panel inputs and outputs. In addition, a 1/4" instrument preamp/direct box input is on the front panel, which will automatically switch the left 500 module's input to this front 1/4" jack once something is plugged into it. Switches to link compressors and engage a 48V phantom supply are also provided. The DocDerr DerrEsser ships with a guitar adapter cable and a standard IEC power cord.