The FAIRCHILD 670 is a highly sought-after vacuum tube compressor limiter that has been faithfully recreated to provide modern producers and audio engineers with the classic sound of the original hardware. Unlike other 670 recreations, the new FAIRCHILD 670 is true to the original.
Utilizing the same tubes and custom wound transformers built to original spec. The architecture, point to point soldering and turret style construction make this the only authentic recreation of the original 670 built and designed by Rein Narma at the behest of Les Paul. We are proud to announce this faithful and meticulous recreation of the original FAIRCHILD 670, The legend reborn.
Each half of the MODEL 670 uses only a single push-pull stage of audio amplification and an extremely high control voltage, with the result that the Automatic Gain-Controlled Amplifier never produces any audible or observable thumps. Contrary to most limiting amplifiers heretofore available, this unit has extremely low distortion and noise under all conditions, both as a straight-through amplifier and under maximum limiting conditions.
The attack time of the unit is made extremely fast in order to catch short transients, and the release time is made adjustable from 0.3 seconds to 25 seconds in six steps. Two of these have release times which are automatic functions of the program material, providing fast recovery for short-duration peaks and an automatic reduction with very long recovery time of overall gain should the program level remain high.
In the circuitry used, each half of the amplifier consists of two separate amplifiers: one is the Automatic Gain Amplifier, and the other provides the necessary power for producing the DC control voltage. Because of this, the controls are somewhat different from those of most other limiters. Essentially there is one control common to both channels which will switch between independent limiting and vertical-lateral component limiting, besides four controls for each channel: a Switch for Metering; an Input Level Control; a Limiting Threshold Control; and an Attack and Release Time Switch.
Owing to the wide choice of attack and release time, as well as the autanatic recovery feature, this unit can be used to limit program material severely without producing the audible thumps or pumping so often associated with limited program material. A limiting meter is provided with provision for connecting a remote meter to the terminals exposed at the rear of the amplifiers. The MODEL 670 is designed to be placed into any normal line level circuit and can be set to have a unity gain at no limiting. Since all critical components are of highest quality, working well below their maximum ratings, a dependable operation can be expected.
INPUT AND OUTPUT IMPEDANCE: 600
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 15kc +/- 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) .2ms / .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.
INSTALLED TUBES: 8x 6386, 2x 12AX7, 4x 6973, 2× 12BH7, 1x E80F or (1xEF806), 1x 5651, 1x EL34, 1× GZ34
