The UREI 1176 Compressor: A Legend in Audio Engineering

The world of audio engineering has witnessed the emergence of countless tools and technologies over the years, but few have left an indelible mark quite like the UREI 1176 compressor.

Designed by the visionary Bill Putnam, this iconic piece of equipment has become synonymous with professional audio excellence. In this article, we’ll delve into the fascinating history, innovative design principles, and enduring legacy of the UREI 1176 compressor.

The UREI (United Recording Electronics Industries) 1176 is one of the most significant and coveted pieces of professional audio equipment in history. The design of the 1176 was conceived by Bill Putnam, who began his work with the independent Universal Recording studio in Chicago.

After establishing himself as one of the best engineers in the United States and with the support of Frank Sinatra and Bing Crosby, he decided to open United Recording Corp in Hollywood and equip it with his unique and innovative designs.

The Genesis and The Vision

Putnam’s early creation, the 108 tube microphone preamplifier, played a pivotal role in shaping the 1176’s design. This preamplifier served as the cornerstone for the development of the 175/176 tube compressor, eventually evolving into the renowned 1176 Peak Limiter.

The first revision of the original 1176, developed by United Recording Electronics Industries (UREI), a company renamed after Bill Putnam moved to Hollywood — was introduced in 1966. UREI started manufacturing a limiter-amplifier using FET (Field Effect Transistor) for gain reduction in a feedback configuration. Four different compression ratios are available: 4:1, 8:1, 12:1, and 20:1.

Attack times range from less than 20 microseconds to 800 microseconds, and release times range from 50 ms to 1100 ms (1.1 seconds). It’s essential to note that, to achieve minimal distortion in this construction topology, an appropriate circuit design is indispensable to stay within the linear margin of equipment operation.

Also read: How To “Calculate” The Compressor Release Time Correctly

Technical Mastery of the 1176

In the specific case of the 1176, in electronic terms, the FET is used as a variable voltage resistor at the bottom of a voltage divider. The resistance between the drain and the source causes the FET to change in response to the voltage applied to the transistor’s base.

The FET is responsible for sending more and more audio signal to ground as compression increases. Following this gain stage is an 1108 amplifier, essentially a pair of Darlington transistors serving as a preamplification stage, and at the output, a Class A amplifier incorporating coupling with a 600-ohm transformer, specially specified by Bill Putnam for the 1176.

The UREI 1176 is a feedback-type compressor, meaning the signal is monitored after gain reduction. The rectified control signal that controls the bottom resistor of the divider is generated in the sidechain circuit, fed from the compressor output, just before the output gain.

This rectified signal is used to feed a capacitor that charges/discharges according to the speeds set in the attack and release controls. The voltage on this capacitor is what controls the bottom resistor of the FET divider.

Operating in feedback, the response of the attack and release ramps varies completely compared to a push-pull system due to its operating principle, making it a program-dependent or material-dependent limiter.

The 1176 stands out as a feedback-type compressor, monitoring the signal post-gain reduction. This design choice, combined with the rectified control signal from the sidechain circuit, creates a program-dependent limiter, where attack, release, and ratio adapt to the input material.

Revisions, Variations, and Industry Impact

Over its history, the 1176 underwent around 13 revisions and variations. Revisions C, D, and E have stood the test of time and are particularly revered among audio professionals for their sonic characteristics.

Around 13 revisions and variations existed in the history of the 1176. Historically, revisions C, D, and E are the most coveted by audio professionals. The equipment developed by UREI has had such an impact on the professional audio community that the 1176LN was included in the TEC Awards Hall of Fame in 2008.

Various manufacturers have endeavored to replicate Bill Putnam’s original design and even add new tools or adapt the design to 500 series modules.

‘All Buttons In’ Mode

One of the sonic characteristics of the 1176 is its particular ‘All Buttons In’ mode, also known as the ‘British mode’ — named for its constant use in British recordings of the 1960s and 1970s. This mode is enabled by activating or pressing all four ratio buttons simultaneously.

The sound of the 1176, especially in this mode, is due to being a program-dependent or material-dependent compressor; the attack, release, and ratio will change depending on the content at the system’s input.

Now, for the ‘All Buttons In’ mode, some peculiarities occur. The ratio will be somewhere between 12:1 and 20:1, so the bias points change throughout the circuit. As a result, attack and release times change. This variation in times, along with the dramatic resulting compression curve, is the characteristic sound of this mode in the 1176.

It follows that the compression curve, at a 4:1 ratio, will have a subtle slope, but the compression curve in ‘All Buttons In’ mode will be almost a straight line. Distortion increases dramatically due to the delay time generated in the attack of the first transients, resulting in the aggressive tone and character of the 1176. This phenomenon could be described as an inverted “look-ahead.”

Versatility Beyond Compression

The 1176 is a limiter-amplifier, which perfectly gives it the authority to function as an amplifier as well. Not selecting any compression ratio would make it behave at 1:1 and work as a line amplifier. It can even function as a microphone amplifier for those transducers with a high output level, such as some dynamic or condenser microphones with their power supply.

Moreover, it is also possible to use it as a distortion box by abusing the input level, resulting in excessively useful and pleasing harmonic distortion throughout the circuit.

The 1176 has been an iconic piece of audio, and several manufacturers have taken on the task of replicating and modifying its circuit. In 2000, Universal Audio introduced the Re-Issue of the 1176 based on Revisions C, D, and E. They also presented an anniversary version of Revision A with a limited batch of 500 units and maintained the 6176, which is a hybrid of the 610 preamp with an 1176LN. Purple Audio has the MC77 based on Revision E.

Warm Audio’s WA76 bases its circuit on the Revision D board but replaces the input and output transformers with Cinemag. Hairball Audio has two versions, one based on Revision A and the other on Revision D.

Gyraf Audio G1176 is a DIY (Do It Yourself) project based on the UREI Revision F but without the Bourns B11148 transformer. IGS Audio’s Volfram Limiter starts from Revision F but with Mix and Sidechain options. Camilo Silva F is also based on Revision F. Klark Teknik has its version of the 1176, based on Revisions D and E.

Many companies base their circuits on the 1176, both in rack and 500 series, but these are some of the most recognized in the professional audio market. Several software emulations of the UREI 1176 compressor are also available, allowing users to harness the iconic sound and functionality of the hardware unit within digital audio workstations (DAWs).

Here are some notable software versions:

Universal Audio UAD-2 1176 Collection

Universal Audio, known for their high-quality audio interfaces and DSP-powered plugins, offers a collection of 1176 emulations. This includes the classic 1176LN, 1176SE, and various other models that faithfully reproduce the characteristics of the original hardware.

Buy at PluginBoutique: 1176 Classic Limiter Collection

Waves CLA-76

Developed in collaboration with Grammy-winning producer Chris Lord-Alge, Waves’ CLA-76 provides an emulation of both the Blue Stripe and Blackface versions of the 1176. It features added modern touches for enhanced flexibility in a mixing environment.

IK Multimedia T-RackS Black 76

Part of the T-RackS mixing and mastering suite, the Black 76 plugin by IK Multimedia emulates the classic 1176 compressor. It provides a simple yet effective interface for users looking to add the 1176 sound to their mixes.

Mellowmuse CP3V Compressor

The CP3V, is a dynamic audio compressor plug-in that draws inspiration from the timeless 1176 analogue compressor. Through meticulously modelled analogue saturation and compression stages, this plugin gracefully infuses your compressed signal with increasing warmth at higher levels, ensuring a rich and inviting sound without ever veering into the harsh territory.

With its ultra-fast attack and release times, the CP3V opens up a realm of creative compression possibilities, allowing your tracks to seamlessly slice through any mix. Elevate your sound with a tool that combines vintage charm with modern precision, giving you the flexibility to sculpt your audio with finesse.

Buy this plugin at Plugin Boutique: CP3V Compressor

Arturia Comp FET-76

Arturia, known for their software instruments, also offers a plugin emulation of the 1176 called Comp FET-76. It provides a user-friendly interface and aims to capture the sonic characteristics of the original unit.

Buy this plugin at Plugin Boutique: Comp FET-76

Brainworx Purple Audio MC77

Widely renowned for its exceptional performance on bass guitars, kicks, vocals, parallel processing, buses, and beyond, the MC77 stands as a testament to the iconic 1176 limiter, and then some.

Starting with an exacting recreation of the revered “E” revision of the 1176, the MC77 preserves the unmatched tone and lightning-fast response of its predecessor.

Buy this plugin at Plugin Boutique: Purple Audio MC77

Also read: Analog vs. Digital Mixing: A Sound Engineer’s Perspective

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Before choosing a software version, consider your specific requirements, DAW compatibility, and the unique features offered by each plugin. Additionally, some DAWs come with their stock compressor plugins that may include 1176 emulations or similar models.

Also, check out discover some free 1176 compressors my list of the Best Free Compressor VST Plugins