Fairchild 670 Tube Compressor/Limiter - Legendary Vintage Recreation
The Fairchild 670 is a faithful recreation of the iconic vacuum tube compressor/limiter that defined the golden age of recording. Originally designed by Rein Narma at the request of Les Paul, this legendary unit is renowned for its smooth, musical compression, rich harmonic saturation, and unparalleled ability to glue mixes together. Built with authentic NOS tubes, custom-wound transformers, point-to-point soldering, and turret-style construction, the Fairchild 670 delivers the classic sound heard on countless hit records — now available to modern producers and engineers seeking the ultimate in analog dynamics processing.
Classic Vari-Mu Compression
The Fairchild 670 uses a variable-mu (remote cutoff) tube circuit with independent vertical and lateral control for stereo disk mastering, as well as standard compressor/limiter operation. Its extremely fast attack and variable release times provide transparent levelling or aggressive character, while the unique time constants (including automatic program-dependent release in positions 5 and 6) deliver natural, musical dynamics. The compression ratio varies from gentle 1:2 to hard limiting up to 1:30, depending on threshold and input level.
Key Features of the Fairchild 670
- Exact historical recreation of the original Fairchild 670
- Vacuum tube design with NOS 6386, 12AX7, 6973, 12BH7, E80F/EF806, 5651, EL34, GZ34 tubes
- Custom-wound transformers and point-to-point/turret construction
- Independent vertical/lateral control for stereo disk mastering
- Extremely fast attack time
- Variable release time with program-dependent auto modes
- Compressor or limiter operation
- High headroom and wide dynamic range
- Balanced 600 Ω input/output impedance
Technical Specifications
- Type: Vacuum tube compressor/limiter
- Input/Output Impedance: 600 Ω
- Range of Input Level: 0 dBm to +16 dBm
- Output Level: +4 or +8 dBVU (+27 dBm clipping point)
- Gain: +7 dB
- Frequency Response: 40 Hz to 15 kHz ±1 dB
- Noise Level: 70 dB below +4 dBm
- Limiting Noises: Below audibility
- Intermodulation Distortion: <1% at any level up to +18 dBm output (no limiting), <1% at +12 dBm output (limiting)
- Attack Time: 0.2–0.4 ms (fixed across positions)
- Release Time: 0.2 s to 25 s (6 positions, including 2 auto modes)
- Compression Ratio: Variable 1:2 to 1:30 (function of limiting and threshold)
- Power Requirements: 120 or 240 V AC, 60 Hz, 3 A
- Tubes: 8× 6386, 2× 12AX7, 4× 6973, 2× 12BH7, 1× E80F/EF806, 1× 5651, 1× EL34, 1× GZ34
