Are KIT Plugins’ BB F66 and F67 convincing emulations of classic Fairchild compressors?$99, kitplugins.com
Released way back in 1959, the Fairchild 660 lays claim to being the world’s first intelligent audio compressor. No, it’s not an early example of AI in the studio, but rather an ingeniously designed processor that can adapt its response based upon the dynamic character of the material passing through. This gives remarkably natural and musically-complimentary results, but the 660 (and its stereo counterpart, the 670) are so exquisitely rare that few are lucky enough to ever see one, let alone use one. If you find a 660 for sale, expect to see a price tag of at least $20k, and twice as much for a 670. Ouch!

READ MORE: ‘What does a compressor do in music?’: A beginner’s guide to compression

Thankfully, through the magic of digital modelling, producers today can add any number of Fairchilds (or close approximations thereof) to a track as a plugin for a fraction of the price. It is surprising, given its revered status, that there have only been a couple of 660 models to choose from, namely Universal Audio’s Fairchild Tube Limiter Collection (UAD only) and Waves’ PuigChild 660/670. But KIT Plugins has now joined the party with its BB F66/67 plugin, priced at a reasonable $99.
What is the F66 plugin?
The F66 is modelled on an original Fairchild 660 unit owned and hand-tuned by John McBride, CEO and head engineer at Nashville’s Blackbird Studios. This explains the “BB” in the plugin’s name and the “Blackbird” branding in place of the Fairchild logo on the plugin window. McBride is also husband to singer-songwriter Martina McBride, and the specific 660 unit modelled for the plugin is an ever-present part of her standard vocal chain, hence the “Martina’s F66” labelling on the plugin.
But the F66 isn’t geared only towards mixing vocals. The tube-based compression of the original hardware is famed for its smooth harmonic richness that sweetens practically anything you throw at it; solo instruments, drum kits, stems, and even full mixes. F66 shares this flexibility and ubiquity.
The F66 plugin
KIT has also done a first class job of recreating the 660’s distinctive timing response options. These are selected via the six-stage rotary Time Constant switch and, like the original, each option gives a different blend of attack and release timings. The first two positions are fast, with 0.2ms attack and 0.3ms or 0.8ms release. The next two positions have a slower 0.4ms attack coupled with longer release times of 2s and 5s respectively.
The final two positions are the most interesting. These give a choice of 0.4ms or 0.2ms attack, along with program-dependent release times that vary based on the dynamics of the incoming audio. Occasional forays above the threshold will keep release times low, but regular peaks will lead to longer release times, thereby preventing the ‘pumping’ sound that compressors can sometimes create.
With positions labelled merely as “1” to “6”, it does take a bit of time to familiarise oneself with the options, and to develop a sense of which works best in different circumstances. The sonic variations between each are usually plain to hear, though. It’s just a case of using your ears.
An optional high-pass filter can be applied to the sidechain signal, which is useful for reducing the plugin’s sensitivity to energetic low frequencies. However, the cutoff frequency of this filter only goes as high as 500Hz, which is a bit restrictive. Enabling the external sidechain option, coupled with appropriate signal routing and filtering, can provide a workaround. But all sidechain work – internal or external – would be made simpler by the inclusion of a sidechain listen.
F66’s simple output stage rounds things off with a Mix control for balancing the source and compressed signals, and a Make Up Gain pot with a -20dB to +20dB range.
The F67 plugin
What’s different about the F67 plugin?
The original Fairchild 660 is a single-channel processor, and whilst the F66 plugin will operate in stereo if added to a stereo track, the better option is to load up the dual-channel F67 variant. Sadly, this isn’t directly modelled on a Fairchild 670 but is instead a doubled-up version of the F66 model. We do think this is fair enough, considering the original 670 consisted of a pair of 660s built into a larger enclosure.
F67 can operate in three modes. In Linked mode, the left channel’s settings are duplicated to the right channel. In stereo mode, each channel operates fully independently. Finally, Mid/Side mode enables mid/side encoding and decoding, allowing each of these components to be controlled independently.
Our only complaint here is that setting up mid/side compression is often made easier by the ability to solo each component but the F67 plugin has no ability to do this. Mid and Sides each have an independent Make Up Gain control which can help a bit in this regard, and you can add an M/S encoder/decoder to your channel or monitor stack for soloing, but having the option built into F67 would be far preferable.

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How do the F66 and F67 sound?
As with the original hardware, the plugins’ compression is progressive, increasing in ratio the further the signal exceeds the threshold, from a gentle 2:1 at-or-around the threshold up to an intense 30:1. Adding extra drive with the Input Gain control results in a wonderfully crushed, gnarly sound that is convincingly analogue-like in character. Running cool or hot, the compression sounds incredibly smooth at all times, yet does not choke-off performance nuances and details.
The plugin also adds a subtle sheen of analogue-like saturation that is uncannily complementary to any sound fed through it. Vocals sound crisp and airy. Drums sound energetic and exciting. Mixes sound classy and coherent. And then there’s the space and life F67’s mid/side mode can infuse into pianos and synths.
Does all of this add up to hyper-accurate Fairchild 660 and 670 emulation? It’s difficult to judge given the rarity of the hardware and the uniqueness of the specific unit modelled by KIT. But it really doesn’t matter one way or the other — when a compressor sounds this great, you’re going to want to use it anyway.
Key features

AAX, AU and VST plugin
Modelled on Fairchild 660 used in Martina McBride’s vocal chain
Includes single-channel F66 and dual-channel F67 variants
Sidechain filter and support for external sidechaining
Undo/redo

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