“PSP NobleQ combines the features of passive program equalizers with a wide range of frequency settings and extended functionality. To make this plug-in a versatile tool we added several modern features such as an adjustable high pass filter, and the ability to switch high peak and shelf filters to Boost or Attenuation operation.
The PSP NobleQ stands out for its warm sound, its boost and attenuation low-shelf filters and its combined peak and shelf high frequency processing. The warm and musical sound in PSP NobleQ is made possible thanks to its finest processing utilizing FAT double sampling for a natural analog-like response. We also added an output valve-like rounding algorithm with adjustable processing depth.
The low shelf filter actually combines two shelving sections: the first one allows you to boost low frequencies while the other one attenuates them but is tuned slightly higher. Together they help to get a rich bottom end without low-midrange muddiness.
The high frequency range consist of two filters – a peaking filter with adjustable band width (usually set to Boost) and a shelf filter (usually set to Attenuate). Both filters interact in such a way that the more attenuation to high frequency is applied the more selective peaking filter becomes while keeping its center frequency similarly boosted.“
More infos here: http://www.pspaudioware.com/plugins/equalizers/psp_nobleq/