The Manley Mastering ED Stereo Variable MU Limiter Compressor has been the best selling product from Manley Laboratories for many years, and is one of the only compressors that have become a standard in Mastering studios and contributed to most hit records over the last decade.  The Variable Mu is a registered trademark for the limiter compressor.  It works by using a "remote cut-off" or re-biasing of a vacuum tube to achieve compression.  

The COMPRESS mode is soft-knee 1.5 to 1 ratio while the sharper knee limit modes start at 4 to 1 and move to a more dramatic ratio of 20 to 1 with the limit is over 12dB.  The knee will actually soften as more limiting is used.  To create distortion simply turn up the input and turn down the output while using very little or no compression.  

Just because the Variable Mu Limiter Compressor has ganged input control, does not mean that it has become mono-unfriendly.  There are separate threshold and output controls to compensate.  When you switch to LINK mode you really get to what the unit can do better than anything else: final mix, 2-track, or mastering limiting and compression.  It really doesn't get much better than this.  Get yours today at Alto Music!

THE T-BAR MODIFICATION

Backstory: The newer Variable Mu units use 5670 tubes instead of the 6386. By now the availability of the original USA GE 6386 is poor; we don't have any left at all, and what we do have are not usable due to noise, microphonics, bad side-to-side match, etc.

So does the 5670 sound different? Well, up to about 6db of limiting it's about the same. After that point, the 5670 version tends to sound more "squashed" than the original 6386 version. Some like it better, some don't - depends on what you're trying to do.

To solve all these problems, Paul came up with a really good solution: the T-Bar Mod. This uses a pair of 6BA6 pentodes wired as single triodes to replace each dual triode 5670 (or 6386).