DerrEsser was Empirical Labs' first product in the API 500 format — the circuit splits the signal into low and high frequency ranges using a crossover technique, then uses a voltage-controlled amplifier (VCA) to turn down excess high frequencies in a way described as unusually musical. Unlike typical de-essers, the same circuit can be used four different ways, switched via buttons on the front panel.
A de-esser that doesn't care about overall level
In DS mode, the trigger threshold doesn't depend on absolute signal level — the circuit compares the amount of high-frequency content to low-frequency content, so raising or lowering the overall level of the chain doesn't throw the setting off. That solves a classic de-esser problem: a threshold dialed in for a loud chorus either misses sibilants in a quieter verse or over-reacts on a loud passage. Here, it's set once and forgotten, because the detector tracks the relationship between bands rather than raw amplitude.
One unit, four different tools
In HF Limit mode, the same circuit works as a high-frequency compressor — level sensitive, but weighted heavily toward high content, delivering general top-end smoothing rather than targeted sibilant control. The Listen function combined with the HP/LP switch lets you actually audition what the dynamics circuit is doing: with the high-pass filter engaged you hear exactly the high frequencies the VCA is controlling, and with the low-pass filter (12dB/octave) you hear only the low end the dynamics never touch. That lets an engineer diagnose which band the problem actually lives in before committing to a threshold setting — something no de-esser without a sidechain-listen function can offer.
KEY FEATURES
- Four operating modes: de-esser (DS), HF limiter, high-pass listen, low-pass listen
- Level-insensitive DS threshold based on the ratio of high to low frequency content
- VCA technology selected for glitch-free, distortion-free, noise-free performance
- Adjustable crossover frequency (Frequency knob)
- 12dB/octave low-pass filter in listen mode
- Bad-Clip indicator monitoring several circuit sections simultaneously (1dB threshold)
- True bypass
- API 500 format, horizontal orientation
- Hand-built and calibrated in the USA
TECHNICAL SPECIFICATIONS
- Frequency response: 3Hz-120kHz (-3dB points)
- Dynamic range: 115dB (from maximum output at 0.5% THD to minimum output)
- Transformerless noise floor: typically -93dBu
- Distortion: 0.0035% to 0.01% depending on mode and settings
- Balanced input, single-ended output with balanced impedance, pin 2 hot
- Input impedance: 20k Ohms, output impedance: less than 51 Ohms
- DS time constants: attack under 1ms, fixed release 0.04s
- Power consumption: 8W max, 4W typical
