Because original units are extremely rare—often selling for over $50,000—many engineers turn to high-quality emulations and modern hardware clones:
There is a reason this unit is synonymous with the "Lead Vocal" sound of the 1960s and 70s. When you run a vocal through a Fairchild, it sits forward in the mix. It sounds present and expensive.
Then there are the sidechain settings (positions 5 and 6), which actually push the attack time slower. This is the secret weapon for bass guitars and drum buses, allowing the low-end thump to pass through uncompressed while controlling the boom of the body. fairchild 670
In a Variable-Mu circuit, the gain reduction element and the gain element are the same thing: remote cutoff vacuum tubes. The Fairchild uses twenty vacuum tubes, eleven transformers, and a massive arsenal of capacitors. It doesn't just "turn down" the signal; it changes the curvature of the tubes' operating points to reduce gain. This happens simultaneously across the audio band.
In an era of digital emulation and "in-the-box" mixing, the Fairchild 670 remains the undisputed holy grail of compression. It is the sound of Sinatra, The Beatles, Pink Floyd, and pretty much every classic rock record pressed to vinyl. But to understand why engineers still mortgage their cars to buy one (or pay top dollar for faithful plugin emulations), you have to look past the legend and into the circuitry. Then there are the sidechain settings (positions 5
: The 670 is a massive 6U rackmount unit featuring 20 vacuum tubes and 11 heavy-duty transformers.
Because the audio never passes through a separate detector, the signal path remains incredibly pure. It offers all the glue and warmth of compression with none of the "chirping" or "breathing" artifacts of lesser units. The Fairchild uses twenty vacuum tubes, eleven transformers,
One of the most revered features of the Fairchild 670 is its attack time controls. Look at the front panel, and you’ll see a knob labeled "Attack Time." It has six positions.
The Fairchild 670 is widely regarded as one of the greatest audio compressors of all time, and its legendary status has endured for decades.
The 670 is not a set-and-forget device.
Many engineers swear by: