ZL Compressor

Name: ZL Compressor
Author: ZL Audio

by ZL Audio · Compressor · Open-source compressor

Not rated yet

ZL Compressor is a free, open-source compressor with four compression styles, real-time peak and RMS displays and an 8-band sidechain EQ.

It has stereo link control and up to 8x oversampling.

Best for: Vocals, Drums, Bass, Mix Bus, Mastering. Genres: all genres.

Keywords: sidechain input, open source, free, bus processing, hybrid topology, vocals, oversampling, visual feedback, built-in analyzer, bass, feed-forward, full mix, mastering, metering, opto, clean, CPU-light, drums, external sidechain, look-ahead, mid/side, mix bus, mixing, pumping, single-band, stereo-linked.

What it does

ZL Compressor is a free, open-source compressor from ZL Audio built around clear visual feedback: real-time peak and RMS displays, a gain-reduction curve and an analyzer. Beyond plain compression it can also inflate, expand and shape dynamics.

Four styles: Clean (feedforward, exponential attack and release), Classic (feedback, exponential), Optical (feedforward, linear) and Vocal (feedback, linear).
Four directions: Compress, Inflate, Expand and Shape; Optical and Vocal are not available for inflating or expanding.
Core controls: threshold, ratio, knee, attack, release, hold, range, makeup gain (manual or auto-learned) and wet mix.
Character controls: Curve sets the non-linearity of the compressed state, Pump shapes the attack stage and Smooth shapes the release stage.
RMS compression: a separate loudness-based mode with its own length, speed and mix settings.
Sidechain: internal or external sidechain, an 8-band parametric EQ on the detector with visual editing, sidechain solo and sidechain gain.
Stereo: mid/side or left/right, either linked or in Max mode, with an adjustable link percentage.
Quality and metering: off, 2x, 4x or 8x oversampling (up to 76 samples of latency at 8x), lookahead, a post clipper, and pre, post and reduction analyzer curves with 6 to 18 second windows.

The current version is 0.6.0. It is free and open source.

Source: ZL Audio product page

When to use it

ZL Compressor is the better pick when you want a deep, visual, all-purpose compressor and don't want to pay. It sits close to Pro-C 3 in approach, with several styles, a sidechain EQ and detailed metering, though Pro-C 3 is the more polished, commercial product. Compared with TDR Kotelnikov, another free favourite, it has a far more detailed interface and extras like inflate, expand and RMS modes, while Kotelnikov is more focused on transparent bus and mastering work. Unlike the 1176 or LA-2A emulations, it models no specific hardware, so you build the character yourself from the style, curve and timing controls.

Best for: general-purpose compression, sidechain-filtered bus compression and upward or downward dynamics work with detailed visual feedback.
Genres: any.
Look elsewhere if: you want the character of a vintage unit with a few knobs; an 1176 or LA-2A emulation fits better, and Pro-C 3 is the more polished commercial option.
Tip: use the sidechain EQ as a high-pass filter so bass doesn't drive the gain reduction, which one KVR user found especially useful.

What producers say

The few users who have reviewed it are very positive, especially given that it is free.

KVR users rate it 5 out of 5 from 2 reviews; one said it beats many paid compressors, another praised the features, low CPU without oversampling and customisable GUI colours.
Criticisms: one KVR user saw occasional GUI freezes on loading, and another asked for features like sidechain delay and more extreme parameter ranges.

KVR user reviews

Where to buy

ZL Audio: Free

Tutorials and reviews

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