At low GR, the 670 acts more like a . At high GR (>10 dB), it becomes a thickening limiter — the go-to for crushing drum bus or parallel compression on vocals.
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 famous for its distinct harmonic distortion. It adds a weight and girth to the low end that is difficult to replicate, while smoothing out the high frequencies in a way that makes them less harsh. It doesn't squash sound; it presents it.
: The 670 is a massive 6U rackmount unit featuring 20 vacuum tubes and 11 heavy-duty transformers.
Most compressors of the era (and today) utilized VCA (Voltage Controlled Amplifier) or Optical (Opto) technologies. They used a separate circuit to detect volume and then tell the gain reduction circuit to turn down the volume. This separation often introduced distortion, noise, or a "pumping" artifact that sounded unnatural.
Because original units are extremely rare—often selling for over $50,000—many engineers turn to high-quality emulations and modern hardware clones:
Fairchild 670 [work] Jun 2026
At low GR, the 670 acts more like a . At high GR (>10 dB), it becomes a thickening limiter — the go-to for crushing drum bus or parallel compression on vocals.
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. fairchild 670
The 670 is famous for its distinct harmonic distortion. It adds a weight and girth to the low end that is difficult to replicate, while smoothing out the high frequencies in a way that makes them less harsh. It doesn't squash sound; it presents it. At low GR, the 670 acts more like a
: The 670 is a massive 6U rackmount unit featuring 20 vacuum tubes and 11 heavy-duty transformers. Plate voltages, balance, and bias need checking every
Most compressors of the era (and today) utilized VCA (Voltage Controlled Amplifier) or Optical (Opto) technologies. They used a separate circuit to detect volume and then tell the gain reduction circuit to turn down the volume. This separation often introduced distortion, noise, or a "pumping" artifact that sounded unnatural.
Because original units are extremely rare—often selling for over $50,000—many engineers turn to high-quality emulations and modern hardware clones: