The Fairchild 670 compressor is a well-known vintage stereo limiter that was released way back in the 1950s by Fairchild Recording Equipment Corporation. This audio compressor's attack and release times are controlled by the switch labeled "time-constant" and the settings are as follows:

Time-constant positionAttack timeRelease time
I​
0.2 ms0.3 seconds (or 300 ms)
II​
0.2 ms0.8 seconds (or 800 ms)
III​
0.4 ms2 seconds (or 2 000 ms)
IV​
0.4 ms5 seconds (or 5 000 ms)
V​
0.4 msadaptive release time A
VI​
0.4 msadaptive release time B


Adaptive release time ATime-constant Position v; attack time = 0.4 ms, release time gradually reacts to the music such that for audio peaks above the threshold it ranges around 2 seconds (or 2 000 ms) and for consecutive audio peaks it adjusts itself up to 10 seconds (10 000 ms)
Adaptive release time BTime-constant position VI; attack time = 0.2 ms, release time gradually reacts to the music such that for audio peaks above the threshold it ranges around 0.8 seconds (or 800 ms) and for consecutive audio peaks it adjusts itself to 10 seconds (10 000 ms), but if the peaks are all over the place then the release time steadily increases up to 25 seconds (or 25 000 ms)

Typical mastering settings for uptempo music​

If you are going to be using the Fairchild 670 compressor you just have to know that the time-constant settings you have to use will pretty much depend on the music you are mastering.

For uptempo and bouncy music such as hip-hop, EDM, pop, and rock music, your best bet is to use time-constant settings of position 1 and position 2. That's because you don't want to make your music less punchy due to extremely long release times.

As for gain reduction, you probably don't want to exceed anything more than 3 dB using the Fairchild 670 in your mastering chain.

Typical mastering settings for dynamic music​

If you are mastering dynamic genres of music such as classical and ambient music, you could, of course, try using time-constant settings of either position 3 or position 4.

The reason for that is time constants of positions 3 and 4 will give you longer release times which is exactly what you want for music that happens to have huge amounts of dynamic range.

Furthermore, if you want to be experimental with the Fairchild 670 compressor then time-constant settings of position 5 and position 6 may suit your needs but be wary of too much gain reduction when using these two automatic release modes.

Some settings for vocals​

In the event that you think of using the Fairchild 670 compressor on vocals make sure you err on the side of caution because this compressor is more suitable for slow vocals.

The main reason why it works best in the context of slow vocals is that the fastest release time you can ever get with it is 300 ms (which is basically time-constant position #1 on the compressor).

So if you want your vocals to be upfront your best shot is to use a faster release time since 300 ms will be way too long. For example, for material like hip-hop vocals and so forth you might want to use something else besides the Fairchild 670 compressor.

At the end of the day, that doesn't necessarily mean you shouldn't ever want to use it but it won't give you that punch like a Urei 1176 compressor.

Below are notable audio software Fairchild 670 plug-ins you may want to try:
  • Overloud Comp 670 (GEM Series)
  • Waves Audio PuigChild 670
  • Universal Audio UAD Fairchild 670
  • IK Multimedia Vintage 670
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