Fairchild 660 Tube Compressor/Limiter - Legendary Mono Dynamics
The Fairchild 660 is a single-channel vacuum tube compressor/limiter that has become one of the most revered and sought-after pieces of audio gear in history. Originally introduced in the 1950s and co-designed by Rein Narma and Les Paul, only around 1000 units were ever built. This faithful recreation stays true to the original specifications, using the same tubes, custom-wound transformers, point-to-point soldering, and turret-style construction to deliver the silky, musical compression, rich harmonic saturation, and unparalleled warmth that made the Fairchild 660 a studio legend.
Classic Vari-Mu Tube Compression
The Fairchild 660 uses a variable-mu (remote cutoff) tube circuit for smooth, program-dependent gain reduction with natural, musical character. Its extremely fast attack and six selectable time constants (including automatic program-dependent release in positions 5 and 6) provide transparent levelling or aggressive limiting. The compression ratio varies from gentle 2:1 to hard 30:1 depending on threshold and input level, making it ideal for vocals, drums, bass, guitars, and mix bus glue.
Key Features of the Fairchild 660
- Exact historical recreation of the original Fairchild 660 mono unit
- Vacuum tube design with NOS 6386, 12AX7, GZ34, 12BH7, 6BL7, 6V6GT, E80F/EF806, 5651 tubes
- Custom-wound transformers and point-to-point/turret construction
- Extremely fast attack time
- Six selectable time constants with program-dependent auto modes
- Variable threshold and compression controls
- VU metering with three switchable positions (plate current or limiting)
- High headroom and wide dynamic range
- Balanced 600 Ω input/output impedance
Technical Specifications
- Type: Vacuum tube compressor/limiter (mono)
- Input/Output Impedance: 600 Ω
- Range of Input Level: -4 dBm to +16 dBm
- Output Level: +4 or +8 dBVU (+27 dBm clipping point)
- Gain: 16 dB
- Frequency Response: 40 Hz to 15 kHz ±1 dB
- Noise Level: 70 dB below +4 dBm
- Limiting Noises: Below audibility
- Intermodulation Distortion: <1% 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 2:1 to 30:1 (function of limiting and threshold)
- Power Requirements: 120 or 240 V AC, 60 Hz, 3 A
- Tubes: 4× 6386, 1× 12AX7, 1× GZ34, 1× 12BH7, 1× 6BL7, 2× 6V6GT, 1× E80F/EF806, 1× 5651
