Reduce Amp Sim Harshness with De-Essing

Reduce Amp Sim Harshness with De-Essing

by Craig Anderton

Feeding too much treble into an amp sim set for a distorted sound can lead to a harsh, brittle timbre due to distorting the high frequencies. Although pulling back on your guitar’s tone control can reduce highs, the tradeoff is often a more muffled sound. Fortunately, “de-esser” processors provide an “intelligent” way to reduce the highs entering an amp sim.

A de-esser’s main purpose is to reduce vocal sibilants (“s” sounds) by compressing only high frequencies, thus lowering the level of sibilants while leaving the rest of the vocal untouched. When placed between a guitar and amp sim, it reduces high frequencies from your axe when they’re prominent, but otherwise doesn’t affect your signal. As a bonus, the compression adds a little additional smoothness and sustain.

Most DAWs have either a compressor that can provide a de-essing function (see Fig. 1), a multiband compressor (see Fig. 2), a dedicated de-esser module (see Fig. 3), or several of these options. If not, you can add a third-party de-essing plug-in.

Fig. 1: PreSonus’s Studio One Pro doesn’t have a dedicated de-esser, but its compressor can do de-essing.

Fig. 2: Ableton Live's Multiband Compressor, like other multiband compressors, can serve as a de-esser by compressing only the high frequencies.

Fig. 3: Clockwise from upper left: MOTU’s MasterWorks multiband compressor, Nomad Factory Blue Tubes de-esser, Pro Tools’ Digirack de-esser, and Waves’ Renaissance de-esser.

A compressor that can de-ess typically has an internal sidechain that puts a filter in the compression detection path, thus filtering out only high frequencies for compression. For example, in Studio One Pro’s compressor, the sidechain section shown in Fig. 1 is in the lower right. It’s set to Internal Sidechain Filter, with a low cut filter that compresses everything above 1.88kHz (ratio 20:1, threshold -48dB). This module also has a “Listen Filter” button that lets you monitor what’s being filtered. This makes it easy to zero in on the frequency range you want to compress.

Dedicated de-essers generally have a subset of a full-blown compressor’s controls, with at least Frequency and Threshold parameters. Adjusting works similarly with all de-essers when applied to an amp sim:

1. Start off with no filtering

2. Set a threshold that's considerably lower than the high-frequency peaks, then slowly extend the high-frequency range that’s being compressed. Note that with some de-essers the threshold control works in “reverse,” with higher settings producing more compression.

3. As you listen to the amp sim output, at some point the sound will become sweeter as the highs start being compressed.

If the compression effect is too obvious, raise the threshold and/or reduce the ratio (if present) to give a subtler effect. When you're done, your reward will be a much sweeter amp sim sound.

Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.