Universal Audio 2-1176 Dual 1176LN - Manual (Page 19)

The Technical Stuff
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History of the 1176
The original Universal Audio 1176, designed by Bill Putnam, was a major breakthrough in limiter
technology – the first true peak limiter with all transistor circuitry offering superior performance and a
signature sound. Evolved from the popular Universal Audio 175 and 176 vacuum tube limiters, the
1176 retained the proven qualities of these industry leaders, and set the standard for all limiters to
follow. In fact, the 1176 may well be the most loved limiter/compressor in history. Its trademark
lightning-quick attack and release times and the tone of its Class A output amplifier have enhanced
countless recordings for more than forty years.
As is evident from entries and schematics in his design notebook, Putnam experimented extensively at
the time with the then newly developed Field Effect Transistor (FET) in various configurations and
eventually found a way of using it as the gain-controlling element of a compressor/limiter. The original
version of the 1176, released in 1967, was denoted the 1176A, but was revised to the model AB only a
few months later, with improvements in stability and slightly reduced noise. The following year saw
revision B, with further minor changes to the preamplifier circuit. These models all featured a brushed
aluminum faceplate with a blue meter section.
1176 Revision B
Revision C, released in September 1970, saw two major changes. One, the unit now sported a black
faceplate instead of silver, and, two, it was now designated an 1176LN, with the “LN” standing for
“low noise.” This model featured the first major modification to the 1176 circuit, designed by Brad
Plunkett in an effort to reduce noise, hence the birth of the 1176LN.
Numerous design improvements followed, resulting in at least 13 revisions of the 1176. Plunkett’s LN
circuitry was originally encased within an epoxy module, but a subsequent redesign fully integrated
these improvements with the main circuit board, resulting in revision D.
1176LN Revision D
Revision E was introduced in the early 1970s and was the first to accommodate European 220V mains
power with a voltage selector on the rear panel. Of all the revisions, model D and model E are
considered to have superior sound and are thus the most sought-after versions by audio engineers.