Extensive compressor reviews and FAQ

Line 6 M13: This is a giant digital multi-fx floorboard. It has all kinds of effects, and five different models of compression, plus a couple of variations on those models. The basic models are: "Red", meant to emulate the MXR Dynacomp; "Blue", meant to emulate the Boss CS-1; "Vetta", which is their own design; "Tube", which is a fat dirty sound that is supposed to be like a vintage tube/optical compressor; and "Boost" which they say is based on the MXR Micro Amp--but with compression and EQ added.
 
Overall the sound quality is pretty good; the noise level is fairly low, the tone isn't bad, and there are some settings where it actually sounds great. The Red model rolls off the lows severely, but has fairly open and present highs; the Blue model has a little better lows, but the highs are muted; the Vetta and Boost both have better lows than the Blue, and the highs are about the same as the Red; and the Tube has massive lows, and OK highs. The Red is clearly meant for guitarists who want a bright sound, and the Blue for guitarists who want a dark sound. The Vetta and Boost have the most natural, flattish frequency response of the group, good for "general purpose" use (including for bassists). Of those two, the Vetta is basic and clean while the Boost allows some extra drive and coloration, as well as having two-band EQ.
 
The Tube model is trickier to describe. It adds a layer of subtle distortion, and pumps the lows. It also has the most gain of all the models, such that I had to set the output level at minimum in order to avoid clipping the rest of my gear. So when I used it to push a tube amp into overdrive, it sounded really terrific--but it was almost unusable with a solid-state rig due to the nasty clipping.
 
Speaking of clipping, the M13 itself can be clipped by a strong input signal, and it's that lovely digital clipping that grates on my nerves like fingernails on a chalkboard. So if you play aggro style, or have an especially high-output bass, you may need to put another compressor (or other volume control) in front of the M13 to avoid that digital glitchy fizzy sound.
 
Just like the majority of other digital comps, it's not so good at peak limiting. You can get some decent limiting in the Vetta mode, with the threshold low, if your playing is steady; but its ratio is only about 3:1, so if you hit it hard and fast (e.g. with slapping), it will certainly not stop those peaks.
 
The other effects in this unit sound pretty good, and it certainly is a convenient package, so I would say the comps are acceptable and sometimes even good-sounding, if you were going to buy the M13 anyway for its other effects--but I wouldn't buy it specifically hoping to get very good compressors in the deal. The clear focus of the M13's design was to load many pedals into one densely-packed floorboard, rather than putting any design effort into making those pedals "better". The Red, Blue, and Tube models have only the basic minimal controls of a typical pedal, with no threshold or input level knobs, so the results you get from each of those models will depend entirely on the signal you feed it. The Vetta has a threshold knob and the Boost has a "drive" (input gain) knob, and these controls make those two models far more useful than the others. It's funny to me that the Boost model has the most controls, when the pedal it was based on has only one knob.
 
The chassis and footswitches are rugged metal, but the rotary encoders (digital knobs) are plastic, and would break easily. There is a metal "roll bar" protecting each group of knobs, but I can still imagine an excited lead singer with cowboy boots accidentally stomping the knobs and causing you an expensive problem. It runs on a proprietary wall-wart power supply, no batteries or daisy-chain supplies will work.
 
There are two bypass modes: "true bypass" and "DSP bypass", and these modes are selected in the setup menu. The true bypass mode is an analog relay switch, so it truly bypasses the effect processing circuitry--however it picks up a lot of extraneous electronic noise, so the "true bypass" actually sounds pretty bad, at least in my EMF-noisy testing room. The DSP bypass allows you to keep the "trails" of reverb and delay effects fading out naturally, rather than being cut off when you hit the bypass. It's also pretty much noiseless, and has no noticeable effect on the tone. So while "true bypass" is something people usually think is better, in this particular case the DSP bypass is actually more usable.
 
Price in USD: new $500, used $250-$350.
 
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