Empirical Labs DS Plus - ELDS-H DerrEsser + EL500 1U Horizontal Rack

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DS Plus
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  • Empirical Labs DS Plus - ELDS-H DerrEsser + EL500 1U Horizontal Rack
  • Empirical Labs DS Plus - ELDS-H DerrEsser + EL500 1U Horizontal Rack
  • Empirical Labs DS Plus - ELDS-H DerrEsser + EL500 1U Horizontal Rack


The DS Plus contains one 500 series DerrEsser horizontal dynamic high frequency fixer fitted into EL500 1U horizontal rack.

ELDS-H DerrEsser High Frequency Fixer

The first entry by ELI into the 500 series format, the DerrEsser is a multi function dynamic filtering device. Available in vertical or horizontal versions.  A perfect fit for our EL500 powered 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 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 powerful circuitry.

The DerrEsser Has Four Modes

DS MODE - (Bypass Button IN, all other buttons OUT). 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.  Easy to set and forget. 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 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, and is probably the first carefully tailored soft knee HF limiter in existence.

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.

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.


  • Possibly the highest performance analog De-esser in existence
  • HF Lim Mode, as well as standard De-Ess – High Frequency limiting with a tailored soft knee. The Dynamic Section can be used for De-essing or smooth high frequency softening
  • A “BAD!” Hard Clip Indicator light – This “Bad” Clip LED lets user know he is within 1dB of hard clipping. It monitors several sections within the DerrEsser for possible clipping
  • Unity Gain in and out – 6dB of gain available
  • Foolproof operation - it's almost impossible to clip or get a bad sound
  • Industry standard API 500 Series Rack compatible
  • True bypass - Know what it's really doing
  • High reliability parts and military grade switches and relays
  • Three year limited warranty
  • Interface and features found nowhere else
  • Hand built and calibrated in USA. Shipping weight 1 Lbs

EL500 Rack

As far as value, it’s hard to beat 500 Series compatible modules.  Their smaller physical size let you get a lot of performance out of a smaller space, they tend to cost less than their larger counterparts, and – the best part – you can customize your own combinations of them.

When ELI started making our own 500 series products, we looked at the power supplies on the market and couldn’t help but notice a need for a better single height dual module rack unit.  On other single height rack units, the modules protrude from the front panel, and don’t look sturdy or attractive. Power supplies were often noisy, frequently reducing the performance of any module mounted in them.  Also, only XLR ins and outs were provided to the user, limiting the device’s applications.

The Empirical Labs EL500 rack eliminates these obstacles.  At the heart of the unit is a super quiet power supply - over 30 dB quieter than some supplies we’ve seen - that will ensure optimal performance from any compatible device.

All 500 series modules will flush mount cleanly in the EL500, providing a much more professional look and feel. The EL500 offers both XLR and phone rear panel inputs and outputs to allow it to interface perfectly with any system.

In addition, a ¼” 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 – a feature we’re sure will prove to be extremely useful. In fact, it has become the first call bass DI for many engineers.  Switches to link compressors and engage a 48V phantom supply are also provided.

Whether you’re already invested in 500 series modules or they’re something you’re thinking about adding to your arsenal, the EL500 rack will make any 500 series compatible module perform ideally and interface effortlessly into just about any audio application.


  • Unique Flush Mount system for durability & looks
  • Super Quiet ± 16Volt Supplies. Perhaps quietest available
  • More than 280mA available on both supplies
  • 48 volt Phantom supply. 35 mA of current
  • Link Switch to Stereo Link two Compressors
  • Built in “Inst In” (Instrument In) for high impedance inputs built into front panel. Direct box built right in!
  • “Inst In” THD is less than .0006%
  • A performing musician can use the INST IN combined with his favorite modules, using the super quality preamp on this front panel jack
  • Auto-Sense on “Inst In” jack
  • XLR & Phone Plug Inputs and Outputs. A total of 9 input and output connectors
  • Front panel Link Switch for Stereo linking dynamic devices such as compressors/limiters/gates
  • Power Consumption – 14 Watts max. 9 Watts Typical with modules installed
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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

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