Gear Spotlight: 1176/MC77 & Alumnus Andrew Roberts

In 1967, Bill Putnam and United Recording Electronics Industries (UREI) released the 1176 Peak Limiter. The compressor was the only solid state peak limiter available at the time. Putnam’s circuit design underwent several revisions and changes, which explains the variety of different 1176 “revs” available today.

Arguably the most popular revisions to the 1176 are revs C, D, and E. These revisions indicated the development of what UREI (now Universal Audio) calls the Low Noise circuit – hence, the “1176LN” title given to the compressors of this era. As of the year 2000, Universal Audio retails an 1176 reissue, based on the Rev C/D/E circuit designs.

The 1176 is a noticeably versatile and “bright” compressor, capable of both a mild, subtle sound (great for using first-to-bat on a vocal, kick, or snare), or highly aggressive and energetic compression. In addition to the standard attack, release, and ratio functions, the 1176 can also be used in what engineers call “British Mode” or “All Buttons In,” in which the four Ratio buttons on the device’s faceplate are pushed downward simultaneously, in theory engaging each ratio setting simultaneously. This technique leads to a compression ratio somewhere between 12:1 and 20:1, but also changes the circuit’s bias points such that the 1176 becomes even more aggressive.

Expanding on these classic characteristics, Purple Audio designed the MC76, their own 1176 revision in 1997. Founded that same year by Music Tech alumni Andrew Roberts, Purple Audio has now updated to the MC77, one of the most faithfully purchased 1176 reissues on the market. These pieces have a rugged, quality-build reputation that certainly doesn’t precede them. Check out the links below for more information, and visit studio A and Studio D to hear our two MC77’s and the 1176 for yourself.

Here are the standard features of any 1176 revision, clone, or DIY build:

  • Variable attack time (between 20µs-800µs)

  • Variable release time (between 50ms-1.1s)

  • Transformer-balanced inputs and outputs

  • Compression ratios of 4:1, 8:1, 12:1, and 20:1 (additionally, somewhere between 12:1 and 20:1 when using “all-buttons-in” mode)

Purple Audio built upon the original 1176 Rev D & Rev E Low Noise designs, incorporating all of the original core features while making these significant additions:

  • Easily accessible and convenient stereo-link function

  • True Bypass (meaning that, when bypassed, signal is dumped directly from the input to the output of the device – signal never passes through the device’s circuitry.)

  • Sidechain/key-input, an extremely useful and common compressor feature.

Audio engineers and electrical engineers alike have taken to online forums to write extensively about the advantages and disadvantages of using one or the other of these units. The full history of the 1176 is linked below, as are the schematics and more information about the MC77.

Useful Links:

Universal Audio’s 1176 Overview

1176 Hardware Revision History

Universal Audio History

UA: All Buttons In Mode

Purple Audio MC77

Purple Audio MC77 Manual & Schematics