Empirical Labs ELDS-H-DERRESSER 500 Series Module - Desser/Dynamic section from LilFrEQ, Horizontal configuration

The DerrEsser is a multi function dynamic filtering device, in an API 500 series module format. In its basic “DS” mode, the DerrEsser is an effective, level insensitive de-esser, which is a device that will adjust the high frequency gain on overly trebly or spiky vocal, or other source. By using a crossover technique, and dividing the audio up into a high frequency range and a low frequency range, the DerrEsser can use its Voltage Controlled Amp to turn down comparatively high or harsh high frequencies in an extremely musical manner. However, unlike other de-essers, the device is not limited to just de-essing, and allows for multi use of its circuitry.

Besides Bypass, there are essentially four modes of the DerrEsser:

DS Mode – (Bypass Button IN, all other buttons OUT). As a de-esser in the DS mode (HF Limit OFF), one can set the threshold 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. In this mode, the dyamic action is “level insensitive”, as the detector circuitry compares the High Frequency content to the low frequency content, Overall signal level doesn’t matter at all. When there is enough HF compared to LF, the threshold is exceeded and the DerrEsser starts to turn down the frequencies above the crossover point set by the Frequency control on the front panel. Again, great care was taken to ensure this DS section meets the Empirical Labs reputation for originality and ease of use. We use the latest technology VCA, specially selected for glitch free, distortion free, and noise free performance. The time constants were carefully selected and the corner frequency is user adjustable with a high performance active crossover.

HF LIMIT – (Bypass Button IN, HF LIM IN, all other buttons OUT). In this mode, the DerrEsser looks at the general level of the High Frequencies only. Think of it 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 can also act as a de-esser but is more of a general high frequency smoothing device.The HF limiter is probably the first carefully tailored soft knee HF limiter in existence. We believe both the DS and HF LIM modes offer the highest performance of any similar device

HIGHPASS – (Bypass Button IN, Listen IN, HP/LP OUT, HF LIM doesn’t matter). By using the “LISTEN” Function, the user can employ the superb 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 by the Frequency knob. Once the LISTEN switch is engaged, all bargraph LED’s should light as indication.

LOWPASS – (Bypass Button IN, Listen IN, HP/LP IN, HF LIM doesn’t matter). 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 by the Frequency knob.

Specifications

• Freq. Response is 3 Hz to 120 kHz (-3dB points).
• Dynamic Range - 115 dB from maximum output (.5%THD soft clipping) to minimum output. Transformerless noise floor typically – 93dBu.
• Distortion Ranges between .0035% and .01% depending on mode and settings.
• DC coupled Input and Outputs
• High quality audio caps used internally.
• Input Balanced, Output single ended but with balanced impedance.
• Pin 2 hot
• Input Impedance is 20k Ohm. Output impedance is less than 51 ohms.
• D-S Dynamics Time Constants - Attack time is less than 1mS. Release .04 sec, fixed internally.
• Power Consumption – 8 Watts max. 4 Watts Typical