FAIRCHILD Model 670

The original Fairchild 670 has a reputation as the best sounding and most versatile compressor ever made. Used on countless hit recordings over the years, its unique combination of tube driven amplification and gain reduction gives the 670 a wide range of compression effects, from subtle and transparent to heavy and pumping. The new vacuum tube Fairchild 670 compressor is faithfully recreated to provide modern producers and audio engineers with the classic sound of the first intelligent automatic volume control limiter. With its dual-channel design and unique compression characteristics, the Fairchild 670 is capable of adding warmth, depth, and character to virtually any audio signal. The vacuum tube technology used in the 670 adds a natural, organic quality to the compressed signal, providing that distinctive classic analog sound to both digital and analog productions.

Key Features:

  • Dual mono/stereo operation
  • Six selectable time constants
  • Threshold, compression, and makeup gain controls
  • VU metering
  • Hand-wired point-to-point construction
  • Custom-designed transformers
  • Tube-driven amplification

Applications:

  • Vocals
  • Drums
  • Bass
  • Guitars
  • Strings
  • Piano
  • Brass
  • Orchestral instruments
  • Mix bus/mastering

TECHNICAL SPECIFICATIONS:

INPUT AND OUTPUT IMPEDANCE: 600 Ω
RANGE OF INPUT LEVEL: 0 dBm to +16 dBm
OUTPUT LEVEL: +4 or +8 dBVU (+27 dBm clipping point)
GAIN: +7dB
FREQUENCY RESPONSE: 40 cycles to 15 kc +/- 1dB
NOISE LEVEL: 70 dB below +4 dBm
LIMITING NOISES: Below audibility
INTERMODULATION DISTORTION: Less than 1% at any level up to + 18 dBm output (no limiting) Less than 1% at dBm limiting +12dBm output
TIME CONSTANT ATTACK AND RELEASE TIMES:
(Note: Positions 5 and 6 release times are automatic function of program material)
Position 1) .2 ms / .3 sec
Position 2) .2 ms / .8 sec
Position 3) .4 ms / 2 sec
Position 4) .4 ms / 5 sec
Position 5) .4 ms / .2 sec individual peaks, 10 sec multiple peaks
Position 6) .2 ms / .3 sec individual peaks, 10 sec multiple peaks, 25 sec consistently high program levels.
COMPRESSION RATIO: A function of the amount of limiting as well as setting of the two threshold controls which can be set to operate at ratios from 1:2 to 1:30
POWER REQUIREMENTS: 120 or 240 volts, 60 cycles AC, 3 amps.
CONTROLS:
a) 2 Input Gain controls: Step attenuator: 1 dB per step.
b) 2 Threshold Controls: continuously variable.
c) 2 Time Constant Switches: 6 positions so as to provide fixed and variable time constants for any type of program material.
d) 2 Metering Switches: 3 positions so as to measure plate current of each control tube, or as a limiting indicator.
e) Mode Switch: A-B positions: 2 independent limiters. Vertical-Lateral position: matrixing input and output, left and right in and out, limiting action vertical-lateral.
f) On-off switch

Installed Tubes: 8x 6386, 2x 12AX7, 4x 6973, 2x 12BH7, 1x E80F or (1x EF806), 1x 5651, 1x EL34, 1x GZ34

Fairchild Model 670 Manual

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