: UTA-D UnFairchild 670M MkII Plug-In

Whoa! A plug-in recreation of the Undertone Audio UnFairchild 670M II vari-mu compressor [Tape Op #125]? Sign me up. The hardware UnFairchild is a beast, ranking highly on my desert island gear list. Eric Valentine [#45, #133], the crew at Undertone, and Mixland <mixland.io> developed the UTA-D UnFairchild 670M mkII plug-in version of the original Undertone Audio hardware 670M II, so confidence is high. But how could a $150 plug-in recreate the tube-driven feed-back-style compression magic of the hardware?

Digging into the exceptionally transparent and insightful material on Eric's Making Records YouTube channel, it's apparent that the development goal with the software version was to replicate the hardware UnFairchild as closely as possible. This is the first plug-in that UTA has developed, and Eric clarified that he wasn't going to build a software version as some cash grab. He set an early requirement that the UnFairchild 670M mkII plug-in would be a tool that he would want to use in his mixes every day.

When pushed beyond their normal operating range, the tubes in the hardware compressor behave with sonic traits that could best be described as non-linear, many of which were challenging to model in software. Eric says that after a full year of calibration, measurement, and matching that they got "pretty goddamn close" to the sound and physics of the original hardware, and my ears agree. Figuring out how to match the harmonic distortion signature of the hardware was the most challenging element of development – even-versus-odd harmonics had to be measured and calibrated in software, with a particular focus on 2nd- and 3rd-order harmonics. The almost intangible, weird, squishy quality of the hardware's characteristic response couldn't always be algorithmically captured. Still, if there were any concessions, it was always in the interest of making the UTA-D UnFairchild 670M mkII plug-in a little more practical when pushed to extremes.

So, what specific features or controls does the plug-in offer in contrast to the hardware version? First, a note: Every single function that the hardware version offers is duplicated accurately in the software, except the Gain Trim, Balance (Bal), and GR Zero meter scale adjustments, which aren't needed in the software. But the plug-in does give DAW users some extras that are not present on the hardware: A post-compression makeup gain option is included for quick and easy level compensation. Also unique to the software version is the ability to adjust the overall harmonic distortion in the signal path. If you need to reduce (or increase!) the amount of color and "heat" introduced, do that via the THD control. The plug-in also includes a wet/dry Mix control, allowing for parallel processing.

The UTA-D UnFairchild 670M mkII plug-in, without a doubt, is my favorite software version of a Fairchild, perhaps because it sounds nothing like the other Fairchild plug-ins I've used. The interaction between the DC Threshold setting and the standard Threshold, plus the variable Attack and Release controls, allows for incredible flexibility. This plug-in presents either the most delicate brush available or the ability to dial in a sandblaster. It excels on vocals and (like its hardware counterpart) shares a supernatural quality that adds immediate energy and heft to vocal tracks. On mix bus compression, using the plug-in's M/S settings provided a stunning and impactful widening effect; it helped me focus the lower frequency elements to create better contrast with the panned elements. And, on the drum bus, I love pushing this plug-in aggressively while using the variable Attack and Release to increase the "splat" and thickness of the drum sound or drawing in some of the room air. I'm stoked about this no-compromise version, and until the enchanted day arrives that I can take delivery of a UnFairchild hardware unit, this will be my go-to surrogate software child.