Mackie ProFX22v2 Owners Manual - Page 15

Owner's Manual there is more protection to your system from distortion and overload due to poor microphone technique (say it ain't so) and general pops, bangs and heavy metal screaming. The soft knee means that the compression slowly ramps up to 6:1 from the threshold. It does not jump abruptly to 6:1, as this would be hard knee compression, and harder on the ears too. The graph on the previous page shows the input signal level going into the compressor, versus the output level coming out of it. It is the typical graph to view when compressors are discussed, and is just the kind of thing our engineers like to discuss during the company Christmas party1. If the compressor is off, then the input = output. For example an input signal level of +5 dBu results in an output level of +5 dBu. The diagonal line from lower left to upper right represents x = y, that is, input = output. 26 27 27. USB Switch [ProFX16v2, ProFX22v2, ProFX30v2] The USB switch on the last stereo channel provides stereo playback of iTunes®, or a DAW via the USB connection. Like any other input, this signal may also be EQ'd, sent to an aux bus, or mixed in with the other signals and assigned to subgroups or main outs. This switch overrides the TRS inputs. At the maximum compression, the threshold is set at 0 dBu, and the input to output relationship is represented by the lower curve. If the input is -5 dBu (that is, below the threshold), the output is -5 dBu. As the input reaches 0 dBu, the output is a bit less than 0 dBu. If the input is +5 dBu, the output is about +2 dBu. If the input reaches +10 dBu, then the output is +3 dBu. Notice the shapely curve of the soft knee between the diagonal slope of x = y and the compressor slope of 6:1 (the compression ratio). The other green curves represent in-between positions of the compressor knob, with higher thresholds before compression begins. Outboard compressors often have controls such as compression ratio, threshold, soft knee/hard knee, attack time, and release time. These last two affect how quickly the compressor kicks in when the input exceeds the threshold, and how quickly it is released after it drops below the threshold. In this compressor, these parameters are specially chosen to give you the best overall performance. Adjust the threshold carefully, so your dynamic range is still lovely, without distortion or overload during the performance. Run through a few practice screams and high-notes, and adjust the compression as required. 1 My High School math teacher, Mr. Marvin, thought that graphs might come in handy for me one day. Finally! Owner's Manual 15