Extensive compressor reviews and FAQ

Rolls GLC (CL151): 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.
 
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 preamp provides up to 20 dB gain. It will not work as an instrument input unless you add your own DI box before the XLR jack. It's a decent clean utility preamp--fairly transparent and not noisy.
 
The other input is a 1/4" jack that can take balanced or unbalanced connections. It only operates at line level, you can't plug a guitar/bass straight in. There's an insert jack for side chain control, and the output jack is another balanced/unbalanced 1/4". The output level control can cut up to -10 dB or boost up to 20 dB, so its output will work with a wide range of devices. If you use the mic preamp, and set both gain knobs to maximum, it can drive a medium-sensitivity power amp.
 
The gate has two controls, for threshold and release time, and one LED to indicate if the gate is open or closed. Unfortunately the gate on this unit seems to be faulty, because I can make the gate open or close by adjusting the threshold knob, but it will not open or close in response to the audio signal (the way it is supposed to).
 
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. There is no loss of highs or lows, and there is not much noise.
 
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.
 

 
 
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