Manley Labs Stereo Variable Mu Limiter/Compressor by LDStudios
I have had a Manley Variable Mu compressor for about 2 years now. It was purchased second hand, and is about a decade old if I am reading the serial number correctly. It features Manley branded transformers on the inputs and outputs, and 5670 valves doing the gain reduction. It is worth noting that there are a few different revisions of this compressor. The earlier models used Sowter transformers and 6386 tubes. 5670's replaced the 6386 valves when supplies became limited, and Manley moved to their own brand of transformers. Other changes include the T-Bar mod which replaces each 5670 with a pair of 6BA6's. Reportedly, the T-Bar mod sounds a lot closer to the original 6386 tubes at higher compression levels. There is also a mid/sid option and high pass filter option as well.
But anyway, on with the review. Lets start with the build quality. It is nothing short of amazing. There are well built units, and then there are units that go that extra mile. The Vari Mu is one of the latter. It screams "I will still be here in four decades time". The faceplate must be 5 or 6mm thick. The internals are beautifully laid out on a thick, heavy traced PCB that is supported by the chassis frame along all edges. It is really a stroke of genius. It allows for fully perforated top and bottom panels on the unit to allow a lot of ventilation, which is terrific! The unit runs quite hot! As an additional nice touch it also allows you to access both sides of the PCB with next to zero disassembly of the unit. Simply remove two screws from the top and bottom panels and they slide straight out! The pots feel solid, though in my non-mastering version there is a slight bit of variation between the left and right controls. The unit comes with modern features like a 110-120v to 220-240v mains switch internally mounted on the PCB. You beauty!
Feature-wise, it has all the usual suspects. A stereo input gain, threshold, attack, stepped release & dual mono output gains. The stereo link feature will compress both channels using the channel with the most gain reduction present. The really interesting part of this compressor is the compress/limit toggle switches on each channel. There is no defined ratio settings, but the manual does describe the toggle as follows; In compress mode, the ratio starts at a soft-knee 1.5:1 ratio. In limit mode, the ratio starts at a sharper-knee 4:1 ratio. I think this feature single handedly has the most profound effect on the way the unit sounds and is operated.
And now onto the sound. Amazing! ...but not without some initial doubts. When I first received the unit I was a little underwhelmed by it. It just seemed neither hear nor there which is a very uneasy feeling for a piece of kit that costs so much! After a little time with it I started to realise that the unit acts very different to other compressors I have in my collection or have spent a lot of time with. Compressors like the Smart C1 react very quickly and precisely to small changes on the front panel. It doesn't take much to "drive" (operate) the unit at all. The vari mu is the complete opposite... small changes are just that. Very small. Its like a big, boisterous stick shift 8V. You have to be the boss! Grab those controls and drive the thing. It really is wonderful when you do.
I attribute this largely to the compress/limit toggle switch. Unlike VCA or FET compression with clearly marked ratio settings, the Vari Mu will increase in compression ratio as you increase the amount of gain reduction. The limit mode starts at a sharp-knee 4:1 ratio but will increase towards a softer knee 20:1 as you hit 12dB of compression. When you combine this reactive ratio with the all valve nature of the unit which can be driven to increase total harmonic distortion, it really opens up some interesting tones and options! For anyone starting out with a vari mu, use the input and output gains! They are probably the controls I tweak the most because the signal level hitting the compression element will alter the degree of gain reduction, the compression ratio and the distortion and tone! In that sense, it drives similarly to an opto compressor like an LA2A... only a lot more fun!
I haven't really found anything that the Vari Mu sounds bad on. It works great in tracking for acoustic guitars, even a bit of bass and I have gotten some really interesting sounds using it on electric. Come mix time, it is equally apt on the stereo mix buss as it is on mono instruments or the drum buss.
All in all, this unit is a keeper. One of those forever kinds of kit. It is built incredibly well and sounds amazing. There are also a variety of options and mods available for it. Manley Labs as a company has been nothing short of amazing to deal with in this regard. For $25 they mailed me out the LED VU mod, something that comes standard with current models. It was quite and easy to install with a slight bit of soldering and looks great. Its a very reassuring touch that Manley Labs is still strongly standing behind a product that has been on the market for over 20 years now.
Get your hands on one and have a play! Here is a cheeky video of some fiddling on a drum bus.