Extensive compressor reviews and FAQ

Rolls CL151 GLC: This is a little utility box, maybe not something you'd have in your main rig, but it could definitely "save the day" if you run out of mixer channels at a gig, or just need a bit of signal processing in a smallish space. GLC stands for Gate Limiter Compressor, and it also contains a mic preamp. It's not a pedal, it's a desktop or rackable module, about the size of a typical DI box.
 
It's a decent clean utility preamp--fairly transparent, with no loss of highs or lows, and not much noise. The mic input is XLR, and it has phantom power if needed. The "on/off" control for the phantom is a small recessed plastic jumper that you have to remove/insert with tweezers or needle-nose pliers. The other input is a 1/4" jack that can take balanced or unbalanced connections. It is meant to operate best when fed a line level signal. There is enough input gain available that you can plug a guitar or bass straight in, however that may mean a higher noise floor; also the low input impedance means you will get dull, dark tone from a passive instrument.
 
The output jack is another balanced/unbalanced 1/4". The output stage has 20 dB gain, so with the additional 20 dB of the input stage, the total allows this preamp to work with a wide range of devices, including driving some power amps. There's also an insert jack for side chain control of the compressor.
 
The gate has two knobs, for threshold and release time, and one LED to indicate if the gate is open or closed. The lower your input signal level, the farther counterclockwise you need to set the threshold knob in order for it to open. The gate opens and closes in a hard chop, so it is only to be used when absolutely necessary.
 
The compressor section also has two controls, for threshold and ratio, and a 5-LED meter to indicate the amount of gain reduction. The threshold knob has a very wide range, and the ratio knob goes from 1:1 to infinity:1, with the high end of that range being the limiter function. At low to medium ratios the compression is smooth and unobtrusive, with no artifacts. At high ratios, though, it starts to distort, as well as muddying the tone. By the time you get to infinity:1 it is all dirt and mud. Going only by my very subjective ears and guessing, I'd say the compressor's clean and useful range is up to about 8:1. In that range it actually sounds quite good, and does its job very well on a wide variety of playing styles.
 
The construction quality is decent, middle of the road. There is no bypass switch. It runs on 12V DC from an external supply. If you need a relatively tiny line-level unit for light to medium compression, or a spare "emergency" mic preamp, this is a good tool for those jobs.
 
Price in USD: new $89, used $40 to $50
 
or on Amazon
 

 
 
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