The Technical Stuff
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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.
Another significant redesign occurred in 1973. The revision F output stage was modified to provide
higher output current capability by using a push-pull circuit design borrowed from Universal Audio's
new 1109 preamplifier. This new output stage replaced the original Class A circuit borrowed from the
1108 preamp. The meter drive circuit was also updated, with an operational amplifier instead of the
previous discrete circuit.
The classic transformer front end of the 1176 met its demise with the model G, in which an
electronically balanced input stage replaced it. The final update, the model H, simply marked a return
to a silver faceplate and the addition of a blue UREI logo.
The companies that Bill Putnam Sr. started—Universal Audio, Studio Electronics, and UREI—built
products that are still in regular use decades after their development. In 1999, Putnam’s sons Bill Jr.
and James Putnam re-launched Universal Audio. In 2000, the company released its first product: a
faithful reissue of the original 1176LN (revision D/E), which quickly garnered rave reviews, finding a
home in hundreds of professional and project studios worldwide. In 2003, the 6176 was released,
combining an updated version of the 610 preamplifier with a limiter/compressor based upon the D/E
revision of the 1176LN, to which a MOSFET regulated power supply has been added in order to
increase bass response and minimize noise.
In 2000, Bill Putnam Sr. was awarded a Technical Grammy for his multiple contributions to the
recording industry. Highly regarded as a recording engineer, studio designer/operator and inventor,
Putnam was considered a favorite of musical icons Frank Sinatra, Nat King Cole, Ray Charles, Duke
Ellington, Ella Fitzgerald and many, many more. The studios he designed and operated were known for
their sound and his innovations were a reflection of his desire to continually push the envelope.
Universal Recording in Chicago, as well as Ocean Way and Cello Studios (now EASTWEST) in Los
Angeles all preserve elements of his room designs.
