Fairchild 660/670
Two model numbers that every plugin bundle has borrowed, and a paper trail that amounts to a few lines of want-ads.
Overview
The Fairchild 660 and 670 are universally recognized and barely documented. The research file for this entry came back with no verified specifications, no production dates, no original pricing, and no confirmed tube complement. So this page sticks to the material that names the models and does not fill the gaps with numbers from memory. What that material does establish is this: the 660 and 670 are two distinct model designations, a mono unit and a stereo unit. Both were established enough in professional limiter circles by the early 1980s that engineers were hunting them on the used market.
The broadcast-equipment classifieds of that era are the best evidence available. Through 1980, the trade papers carried standing "want to buy" listings naming the Fairchild 660 and 670 alongside the Teletronix LA-2A, Universal Audio 175/176/177, UREI 1176LN and LA-3A, and the RCA BA-6A. That was a roll call of the period's most sought-after level-control gear, and the Fairchilds sat in the middle of it. One buyer, listed in Brighton, Massachusetts, ran the same request across multiple issues that year. These units were apparently hard to pry loose even then.
The reputation lasted. Mix (2011, p.92) carried an advertisement for the ADL 670 stereo tube limiter, pitched as designed in accordance with the original Fairchild 670. That is a modern manufacturer building its identity around the original's circuit concept. The same era of the magazine shows the name in studio gear lists, with Fairchild 660 and 670 emulations appearing as plug-ins in working studios' processor inventories.
What the archive cannot do is tell you what's inside one. No service manual, no owner's manual, and no period review with measured performance surfaced in the research for this entry. The want-ads establish desirability; the reissue advertising establishes enduring reputation; neither establishes a single hard specification. Anyone who needs the tube lineup or the attack and release behavior will have to find a schematic, and this page will not invent one. The honest portrait the sources support is a pair of limiters whose standing in the trade was so thoroughly settled by 1980 that engineers were running standing ads for them — and whose technical record, at least here, remains blank.
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