The Fairchild 670 is widely considered the "Holy Grail" of studio compressors, renowned for its lush, tube-driven warmth and smooth musicality. Originally built in the late 1950s by Rein Narma and Les Paul, this 65-pound "tube monster" features 20 vacuum tubes and 11 transformers, making it one of the most complex and expensive pieces of vintage audio gear. The Legend of the Fairchild 670 The "Holy Grail" Sound
With 20 tubes, expect regular recalibration. Plate voltages, balance, and bias need checking every few months in active use. Most modern clones include trim pots for this.
The 670 is not a set-and-forget device.
What makes it special is how it — rather than sounding like an effect, it makes tracks sound finished . The combination of program-dependent timing, tube harmonic saturation, and transformer warmth creates a sense of “rightness” that digital emulations still chase.
The is the closest production unit under $8k. The UAD plug-in is used daily on hit records — but lacks the non-linear low-end response of hardware. fairchild 670
The original units are maintenance nightmares. They run hot, the tubes are expensive, and the capacitors can drift. Yet, the sound is so coveted that companies like Universal Audio have spent decades modeling the non-linearities of the transformers and the specific distortion characteristics of the tubes.
The 6 positions are approximate RC time constants, but the actual release varies with program material. Position 3 might release in 150 ms on a snare hit but 300 ms on a bass note. The Fairchild 670 is widely considered the "Holy
If you ask an engineer to describe the sound of a Fairchild, you will often hear the word "sweetening."
Unlike later VCA or optical designs, the 670 controls gain by varying the bias voltage on remote-cutoff pentodes (6386s), which changes their plate resistance — a smooth, non-linear, musical gain reduction. Plate voltages, balance, and bias need checking every
Modern digital compressors often offer attack times measured in microseconds (0.000001s). But the Fairchild’s fastest attack time is . That might seem "slow" compared to modern standards, but it is a sweet spot.