F could only ever be for Fairchild. If for no other reason that this plug-in is the most UAD-ish of all the UAD plug-ins. What I mean by that is that UAD are best known for meticulous software recreations of classic analogue equipment. Equipment which is often vintage and sometimes so rare and eye-wateringly valuable (I won't say expensive because that suggests it's for sale and in the case of a Fairchild, even if you have the money, people who have them aren't selling!) that most people haven't seen one in the flesh, let alone used one. Of course once you have an accurate plug-in you can take your virtual Fairchildren and use them as channel compressors until your DSP gives up. Try that with hardware!

If we were to look at which countries have contributed the most to the history of audio gear the top two would probably have to be the USA and the UK or Germany (discuss...). The Swiss and Japanese would definitely get a mention but I nominate Estonia.

History

The Fairchild 660 and 670 were designed by Estonian born Rein Narma. The design was originally commissioned by Les Paul (as if audio needed another reason to thank Mr Paul for his legacy). It was picked up by Fairchild, who licensed the design and hired Narma as chief engineer.

The Fairchild was always an expensive and rare beast. Big, over-engineered and designed to be an ultimate compressor (14 transformers and 20 valves in a 670). Unlike many of its contemporaries, this compressor/limiter was fast. At the time the Fairchild was designed transistors were still in their experimental phase and super-fast designs like the 1176 wouldn’t become available for over a decade. While these days the value of a Fairchild is in its venerated sonic signature, so much so that many producers have gone on record saying that they use it as a tone box, not compressing at all, in the 50’s the Fairchild was fast and offered a way to catch peaks that lesser compressors couldn’t. 

Attack, Release, Ratio And Threshold

There is no direct access to attack and release times, the time constants control offers 6 presets with progressively longer attack and release times. 5 and 6 have programme dependent release times. The Fairchild approaches control of ratio and threshold in a similarly unconventional way, with no direct control over ratio. Arguably the Fairchild is a limiter rather than a compressor but using the D.C. threshold control the hard knee can be softened to such an extent that the unit behaves as a compressor with a progressively increasing compression ratio throughout the entire dynamic range, approaching but never quite reaching limiting.

Control of threshold is potentially confusing as it appears to combine the variable threshold of modern compressors with variable input gain (usually in conjunction with a fixed threshold) as found in the 1176. The threshold control on a Fairchild works in reverse, with a clockwise turn lowering the threshold and giving more gain reduction, much like a Drawmer. The same amount of compression can be achieved with a low input gain and a low threshold as with a high input gain and a high threshold. The difference between the two scenarios is one of harmonic content as setting the input gain control high will overdrive the input stage and offer potentially useful distortion. The input and output characteristics weren't modelled in the legacy plug-in, so this distinction only applies to the newer UAD2 plug-ins.

The Fairchild can operate in L+R or M/S modes. The M/S mode would have been particularly useful in disc cutting applications where the up/down and side to side movements of the cutting lathe can be controlled and it is in this application that I’m sure significant numbers of this advanced and expensive hardware would have been used in the 50’s.

Plug-in Versions

The three plug-in versions available from UAD are the 660, 670 and the 670 Legacy. The 660 and 670 are meticulously modelled to component level using the extra power offered by the UAD2 platform, the 670 Legacy didn’t model the input and output characteristics, dating as it does from the original UAD hardware, and offers a cleaner sound with a correspondingly lower CPU demand and because it doesn’t use the internal upsampling techniques common to many of the newer UAD plug-ins it also offers lower latency.

To hear the Fairchild collection plug-ins in use, check out Russ’ video review.