Manley Stereo Variable Mu Limiter Compressor with MS Mod is the standard version of the valve compressor extended with the MS modification, which adds mid-side encoding and decoding inside the unit itself.
Compressing only what is in phase
A mix with vocal and kick in the centre and guitars and ambience out at the sides responds to stereo compression in ways that are hard to predict: you press on the middle and the image narrows along with it. The MS modification splits the signal into sum and difference before the gain stage, so you can compress the in-phase content alone and leave the sides untouched. The result is a mix that grows denser in the centre while sounding subjectively wider, because the difference material was never touched. The same tool works the other way when overspread sides need reining in.
The valve itself as the gain control
A variable mu circuit has neither a VCA nor an optical cell. Gain changes through the bias voltage of remote cutoff valves, so the reduction is not applied to the signal, it is how the amplifying stage behaves. That produces the characteristic response: the harder you push it, the gentler the curve looks, instead of a hard knee at the threshold. The mode switch gives 1.5:1 in Compress and 4:1 to 20:1 in Limit, attack is continuously variable from 25 to 70 ms, and recovery has five settings: 0.2 s, 0.4 s, 0.6 s, 4 s and 8 s. A high pass filter in the sidechain at -3 dB @ 100 Hz keeps the low end out of the detector so the kick does not drive the whole mix.
KEY FEATURES
- MS modification with mid-side encoding and decoding
- Compression of in-phase content alone to widen the image
- Two channel compressor and limiter with an all-valve path
- Compress mode at 1.5:1 and Limit mode from 4:1 to 20:1
- Attack continuously variable from 25 to 70 ms
- Recovery in five steps: 0.2 s, 0.4 s, 0.6 s, 4 s and 8 s
- High pass filter in the sidechain at -3 dB @ 100 Hz
- Manley IRON transformers with nickel laminations
- Channel linking for stereo operation
- Hardwire bypass for comparison against the unprocessed signal
- Illuminated Sifam gain reduction meters
TECHNICAL SPECIFICATIONS
- Variable gain valves: 5670 x2 in the standard version
- Amplifying valves: 5751 or 12AX7 x2
- Output valves: 12BH7 x2
- Sidechain rectifier: 12AL5 x2
- Frequency response: 20 Hz to 25 kHz (±0.1 dB)
- Maximum gain: 35 dB
- Maximum output: +30 dBu with 26 dB of headroom
- THD: below 0.1% at 1 kHz
- Noise floor: -85 dB typical
- Balanced inputs and outputs, 600 Ohm
- Controls: conductive plastic potentiometers, continuously variable
- Dimensions: 19 x 3.5 x 10 inches, 2U; power consumption 80 W
