Loosely based on the old Fairchild limiters, the Manley Variable MU uses a remote-cutoff tube to do the actual gain reduction rather than a VCA or optical cell. Very widely used for recording vocals and for processing of the entire stereo bus by mixing and mastering engineers worldwide.

The switchable sidechain high-pass filter was made standard at the end of 2009. All Variable MUs from 2010 to the present day shipped with this filter. Original units used the 6386 tube (same as the Fairchild 660 / 670), though most units use the 5670 for gain reduction. The "T-BAR" mod replaces these tubes with 6BA6 for a compression curve more closely matched to the original 6386 units when more than 6dB of compression is applied.

A mastering version with all stepped controls (except for dual input gain) is also available as a custom order.