HLABS CL089 500 Series PWM Compressor

Vintage Swiss PWM compression. Reborn for the modern studio.

The HLABS CL089 is a fully analogue, single-channel 500 Series compressor that brings the distinctive Pulse Width Modulation (PWM) compression technology of the legendary Studer 089 mixing console into the modern recording studio. Inspired by the original Swiss design introduced in 1968, the CL089 combines exceptionally fast, precise dynamics control with the rich, characterful sound of a discrete output stage.

Featuring a custom H101 discrete operational amplifier, a Lundahl LL1588 output transformer and an authentic Studer-inspired PWM compression circuit, the HLABS CL089 offers a compelling combination of transparency, punch and analogue character.

Faithful to the original where it matters, yet enhanced with modern studio functionality, the CL089 is equally suited to subtle dynamic control, assertive compression and limiting.

Key Features

• Vintage Studer 089-inspired PWM compression with a fully analogue signal path

• Four compression ratios: 1.5:1, 2:1, 5:1 and LIMIT (>20:1)

• Two attack modes: original 0.6 ms fast attack and additional 10 ms slow attack

• Five release settings: 0.1 s, 0.3 s, 0.75 s, 2.0 s and Auto

• 120 Hz sidechain high-pass filter for improved low-frequency dynamics control

• Custom H101 discrete op-amp inspired by the original Studer A101 design

• Lundahl LL1588 output transformer for an open, powerful and characterful output stage

• TANDEM stereo linking for operating two CL089 compressors as a stereo pair

• Extended input attenuation and output make-up gain for flexible gain staging

• Socketed 2520-compatible op-amp allowing alternative compatible op-amps to be installed

• Relay-operated bypass and distinctive incandescent gain reduction indicator

• 99% through-hole construction, designed and assembled in France

A Legendary Swiss Compression Circuit, Reimagined

The story of the HLABS CL089 begins with the Studer 089 mixing console, introduced in 1968. Developed during a period when Swiss broadcast and recording engineers demanded exceptional accuracy and reliability, the Studer 089 became known for its transparent yet dynamic sound.

At the heart of its master section was a remarkable compressor/limiter based on Pulse Width Modulation, an unusual approach to analogue dynamics processing that remains rare in professional audio equipment today.

Rather than simply recreating the appearance or general character of a vintage compressor, HLABS has revisited the underlying circuit topology. The CL089 retains the essential characteristics of the original design while introducing additional control and flexibility for contemporary recording and mixing applications.

The result is a distinctive 500 Series analogue compressor with a genuine historical pedigree and a sonic character that sets it apart from conventional dynamics processors.

PWM Compression: Fast, Transparent and Full of Character

Unlike traditional VCA, FET or optical compressors, the HLABS CL089 uses Pulse Width Modulation (PWM) to control gain.

PWM works by switching the audio signal at a frequency far above the audible range and varying the width of the resulting pulses. Following filtering, the signal is reconstructed at the required level. This technique provides extremely fast and accurate gain control while maintaining excellent transient handling and high-frequency detail.

The CL089 draws on the philosophy of the original Studer design: transparent and unobtrusive compression that preserves the integrity of the source material without sacrificing musical impact.

But transparency does not mean an absence of character. The CL089 combines its controlled, precise dynamics processing with a substantial and unmistakably analogue output stage, giving recordings a sense of solidity, richness and punch.

Discrete H101 Op-Amp and Lundahl Transformer Output Stage

A defining feature of the HLABS CL089 is its carefully designed analogue output circuit.

To recreate the character of the original Studer electronics, HLABS developed the H101 discrete operational amplifier, inspired by the legendary Studer A101 used in classic Swiss recording equipment.

The H101 drives a premium Lundahl LL1588 output transformer, creating a powerful, open and characterful signal path.

Importantly, the sonic contribution of this output stage is not dependent on heavy compression. Even with minimal gain reduction, the H101 and Lundahl transformer combination contributes its own distinctive character to the passing audio signal.

The H101 is also mounted in a socket compatible with the industry-standard 2520 footprint. This allows users to experiment with alternative compatible discrete op-amps, offering further possibilities for tailoring the compressor's output-stage character.

Vintage Compression Controls with Modern Flexibility

The HLABS CL089 preserves the four original compression ratios of the Studer-inspired design: 1.5:1, 2:1, 5:1 and LIMIT.

These settings provide a useful range of dynamics control, from gentle compression and restrained level management to considerably more assertive gain reduction.

The original 0.6 ms attack time delivers exceptionally fast response, while the additional 10 ms Slow Attack mode offers greater flexibility when working with transient-rich material.

Five release settings, including an automatic release mode, allow the compressor's recovery behaviour to be tailored to the programme material.

A switchable 120 Hz sidechain high-pass filter reduces the influence of low-frequency energy on the compressor's detection circuit. This is particularly useful when processing material with strong bass content, where excessive low-frequency triggering can result in unwanted gain reduction.

Extended input attenuation and output make-up gain controls provide additional flexibility for integrating the CL089 into modern recording and mixing workflows.

Stereo Compression with TANDEM Linking

Although the HLABS CL089 is a single-channel 500 Series compressor, its built-in TANDEM mode allows two CL089 modules to be linked for stereo operation.

This makes the CL089 an option not only for individual recording channels but also for stereo sources, subgroup processing and stereo bus compression.

Using two modules provides access to the same PWM compression topology and transformer-based output character across a stereo signal path.

Authentic Analogue Design, Built in France

The HLABS CL089 has been designed with respect for the original Studer engineering philosophy.

Its fully analogue signal path and approximately 99% through-hole construction reflect a deliberate approach to preserving the character and construction principles of the vintage circuit.

Even the gain reduction indicator takes a distinctive approach. Rather than using a conventional LED display, the CL089 features a small incandescent lamp that responds visually to the amount of compression being applied.

Designed and assembled in France, the CL089 brings together vintage Swiss-inspired circuitry, discrete analogue electronics and modern 500 Series convenience.

Alongside the HLABS PRE169 microphone preamplifier and EQ169 equaliser, the CL089 completes the company's Studer-inspired 500 Series signal chain.

HLABS CL089 Technical Specifications

Frequency response specified with a 1 kΩ load and light compression.

Frequently Asked Questions

What type of compressor is the HLABS CL089?

The HLABS CL089 is a fully analogue 500 Series compressor that uses Pulse Width Modulation (PWM) gain reduction. Its circuit is based on the compressor/limiter design found in the vintage Studer 089 mixing console.

Can the HLABS CL089 be used for stereo compression?

Yes. Two HLABS CL089 modules can be linked using TANDEM mode for stereo operation. Each CL089 is a single-channel compressor, so stereo processing requires two modules.

What makes PWM compression different from VCA or FET compression?

PWM compression varies the width of high-frequency switching pulses to control audio gain. In the CL089, this technique enables fast, precise dynamics processing with excellent transient handling and preservation of high-frequency detail.

Does the CL089 add analogue character without heavy compression?

Yes. The H101 discrete op-amp and Lundahl LL1588 output transformer form a characterful analogue output stage. Their sonic contribution can be heard even with little or no gain reduction.

Is the HLABS CL089 a recreation of the original Studer compressor?

The CL089 is closely based on the original Studer 089 PWM compressor circuit, preserving its fundamental topology, compression ratios and release characteristics. HLABS has also introduced modern features including slow attack, a 120 Hz sidechain high-pass filter and extended gain controls.

Where is the HLABS CL089 manufactured?

The HLABS CL089 is designed and assembled in France.