Manual

The Technical Stuff

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We here at Universal Audio, have two goals in mind: to reproduce classic analog recording equipment

vintage analog technology. Today we are realizing those goals, bridging the worlds of vintage analog

and DSP technology in a creative atmosphere where musicians, audio engineers, analog designers

and DSP engineers intermingle and exchange ideas. Every project taken on by the UA team is driven by

its historical roots and a desire to wed classic analog technology with the demands of the modern

digital studio.

6176 Overview

The 6176 is a channel strip that combines a vacuum tube microphone/instrument/line preamplifier

with a solid state FET-based limiter/compressor.

Its creation was based on a simple idea: Put an 1176LN circuit in the output section of our 610 mic

preamp. This effectively marries two faithful reissues of vintage audio devices revered by engineers.

The 610 has a long lineage of its own, based upon the original 610 console built by Bill Putnam Sr.

Similarly, the 1176LN has long been, in the words of legendary engineer Andy Johns, “the workhorse

compressor” in hundreds of studios the world over.

The function of a preamplifier, as its name implies, is to increase (or amplify) the level of an

incoming signal to the point where other devices in the chain can make use of it. The output level of

microphones is very low and therefore requires specially designed mic preamplifiers to raise their

level to that needed by a mixing console, tape recorder, or digital audio workstation (DAW) without

degrading the signal to noise ratio. This is no simple task, especially when you consider that mic

preamps may be called upon to amplify signals by as much as 1000%.

Accomplishing musical-sounding compression is no simple task, either, and a number of different

circuits have been developed through the years to attain that goal. One of the most unique of these

designs is the one Bill Putnam, Sr. created for the original 1176 limiter/compressor (upon which the

6176 limiter/compressor is based). The naturally “edgy” sound of the 1176 came from the fact that it

used a line level input transformer and an FET for gain reduction, followed by another gain stage. For

those reasons, regardless of source material, the 1176 will affect tonal quality. In fact, some

engineers use the 1176 just as a tone box, and turn off the compression.

Perhaps even more importantly, the effect of the gain reduction circuitry in the 6176 (as in the 1176)

is program dependent—a big part of its musically pleasing sound. Although the 6176 compression

ratio and attack and release times are user selectable, their responses vary according to the changes

in the incoming signal. The circuitry will faithfully compress or limit at the selected ratio for

transients, but the ratio will always increase a bit after the transient, though to what degree is once

again program dependent. The basic controls for the 1176 are Input, Output, Attack and Release. The

Input knob doubles as the threshold control. The Output knob sets make-up gain and, therefore, the

final output level. However, cranking up the Input knob also affects post-compression output levels.

It’s a balancing act that quickly becomes familiar.

Through careful attention to design, custom wiring, and the use of vacuum tubes which are carefully

selected and tested individually, the 6176 provides a powerful second-generation recording tool with

a clarity and punch that makes it an ideal front-end for tracking with modern DAWs. Its simple

operation, combined with its unique limiting/compression characteristics gives it the same extremely

musical control that has made the 610 and 1176 such well-loved classics for over 40 years.