When it comes to compressors, the Fairchild 670 is one of the most highly coveted modules ever made. With only 500-1000 ever made, original vintage units are extremely hard to come by, and often carry a hefty price tag. Thankfully, in recent years, companies like UnderTone Audio and Heritage Audio have come to the rescue with authentic and affordable recreations of the classic Fairchild design.

In our latest video, Vintage King Audio Consultant Cody Angel shows off the UnderTone Audio UnFairchild 670M II and the Heritage Audio HERCHILD 670 at the Vintage King Nashville Showroom. Check out the video below for audio clips of the full mix, drums, bass, and more.

Fairchild 670 Tube Compressor

Originally designed in the 1950s, the Fairchild 670 is a single-channel compressor built around a series of RCA 6386 tubes. The 660's calling card was its fast attack and slow release times, which made it an ideal broadcast limiter, protecting transmission towers from explosive transients that could damage transformers. 

This characteristic also made it perfect for mastering mono records. However, as the industry standard shifted to stereo records, a two-channel version was needed in order to cut stereo lacquer masters. Enter the Fairchild 670.

Featuring a full complement of 20 tubes, 11 transformers, and two inductors, the Fairchild 670 splits the two channels via a matrix network, limits them separately, then recombines them through another matrix to reconstitute the stereo signal. The stereo-processing method allowed the 670 to maximize the use of the stereo groove space, making records louder with less distortion. 

UnderTone Audio UnFairchild 670M II Tube Compressor

UnderTone Audio, the brainchild of famed producer and engineer Eric Valentine(Smash Mouth, Good Charlotte, Queens of the Stone Age), has lovingly recreated the legendary Fairchild compressor with the best-selling UnderTone Audio UnFairchild 670M II.

Beloved for its simple yet effective design, the UnFairchild uses only two transformers and four paralleled vari-mu tubes to provide everything from gentle smoothing to explosive, energizing compression. 

UnderTone has made careful adjustments to the circuitry to improve the lifespan and reliability of the tubes and added features such as six original preset time constants and four variable time constants, MS function, side chain processing, and user-adjustable "DC Threshold" and "Feed-Back" vs. "Feed-Forward" functionality. 

Heritage Audio HERCHILD 670 Tube Compressor

The Heritage Audio HERCHILD 670 Tube Compressor is a modern take on the classic Fairchild sound. Based on 22 valves and 9 transformers, the HERCHILD Model 670 provides a warm and familiar tone that engineers and producers love.

Heritage Audio has successfully traced the original design and components to faithfully reproduce the exact attack and release times of its ancestor. The HERCHILD Model 670 also includes some practical additions, such as direct access to the continuously variable slope control and the SC FILTER, which provides four different frequencies to choose from.

This two-channel unit can be used independently or linked together in four different modes of operation, providing a whole new world of options to your mix, including dual mono, stereo, mid/side, and the innovative LAT/VERT LINK Mode.