Empirical Labs EL500 Plus

Empirical Labs EL-DS DerrEsser
The DerrEsser from Empirical Labs is a multi-function dynamic filtering device, in an API 500 series module format.  Perhaps the most flexible de-essing tool available, in its basic "DS" mode, the DerrEsser is an effective, level-insensitve de-esser that adjusts the high frequency gain on overly trebly or spiky vocals, or other source.  By using a crossover technique, and dividing the audio up into a high frequency range and a low frequency range, the EL-DS 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 ELDS is not limited to just de-essing, and allows for multi use of its circuitry. It also features a high-frequency limiter that can almost entirely remove unwanted fret and finger noise from dynamic acoustic guitar performances, as well as tame aggressive, diaphragm-shaking vocals, in a very musical way.

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 EQing to make a vocal sound aggressive and clear. In this mode, the dynamic 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.  Great care was taken to ensure this DS section meets the Empirical Labs reputation for originality and ease-of-use by employing 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's 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.  Both the DS and HF LIM modes offer what is perhaps 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 bar graph 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 12dB-per-octave filter whose corner frequency can again, be adjusted by the Frequency knob.

Empirical Labs EL 500
The EL500 is a horizontal rack for 500-series modules that complies with API’s VPR Alliance specification—so it will work with nearly all 500-series modules.  Like all Empirical Labs products, it goes the extra mile, giving you not only a two-space power rack, but also a built-in front-panel DI for high-impedance inputs, such as guitar and bass.  The DI has an auto-sensing impedance circuit to prevent loading you pickups.

The EL500’s unique design also allows 500-series modules to mount flush with the its front panel, which brings the look of your 500-series modules uptown by eliminating unsightly edges—makes your 500 gear look like a finished rackmount unit.

The EL500 also features ultra quiet ±16V power supplies—perhaps the quietest around, plus a 48V phantom power supply. It has a front-panel Link switch that lets you stereo-link two dynamics devices, such as compressor/limiter/gates, or two DerrEssers.  On the back panel, there are balanced XLR and 1/4" TRS inputs for each slot, balanced XLR outputs, and active unbalanced 1/4" TS outputs for a total of eight back-panel inputs and outputs.  For global use, the EL500 has a voltage-select switch inside the unit.
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