As mentioned, each channel of the Vitalizer has its own controls (channel 1's controls are on the left side of the front panel, and channel 2's are on the right). The first of these controls is the Active button. This is nothing more than a backwards bypass switch. Instead of pressing it to bypass the processing, press it to make the processing "active." An LED above the button illuminates to indicate that the processing is "on-line." The next button is the Process Solo button. When pressed, only the processed signal is heard. Otherwise, the direct signal is mixed with the processed signal. An LED above this button also lights to indicate that the processed audio is being "soloed." This is a handy function of the Vitalizer. As you're well aware, anytime you begin tweaking some audio with any kind of equalizer, it becomes necessary to compare the processed version with the unprocessed version to help keep a healthy perspective of what you're doing. The Process Solo buttons make that easy. Also, should the Vitalizer be installed on an effects bus of your console, the Process Solo button must stay pressed in order to return only the processed signal to the mix.
To the right of the Process Solo button is a Peak LED which lights at 3dB before clipping in the processor chain. To the right of this is the Output Level/Process Depth control. This dual-concentric control is like many Balance controls -- the outer knob controls one function or channel, and the inner knob controls another function or channel. In this case, the outer knob is the Output Level control, and the inner knob is the Process Depth control. The output level is generally set wide open then backed off when excessive processing requires attenuation of the overall output level.
The Process Depth control sets the amount of processed signal that is added back to the mix. However, this control only affects the Sub-Bass and Mid-Hi Tune controls. The Harmonics and Stereo Width functions are not affected by the Process Depth control. The Process Depth function is much like the Dry/Wet mix control found on many processors.
To the right of the Process Depth/Output control is the Deep button which is used together with the Sub-Bass control next to it. The Sub-Bass control, as you'd guess, takes care of your low frequency needs but in a unique way. When the control is in its center position, pointing straight up at the zero, there is no effect. As the control is turned to the right, a tight, punchy bass is added to the mix. When turned to the left, the bass added seems more deep, and "boomy." The Deep button changes the frequency range that is affected by the Sub-Bass control, so you end up with four different low frequency ranges to play with. The amount of bass added to the mix is determined by the Process Depth control.
To the right of the Sub-Bass control is the Mid-Hi Tune control. Using psychoacoustic principles, the Mid-Hi Tune control attempts to achieve a sense of increased loudness. The range of the control is from 22kHz when turned completely counter-clockwise, to 1kHz in the full clockwise position. The control sets the lower frequency limit at which processing takes place. So, when set at the full counter-clockwise position of 22kHz, there is no audible processing because the processing is being limited to those frequencies above 22kHz. As the control is turned clockwise, more and more of the audible frequency spectrum is processed. As with the Sub-Bass control, the amount of Mid-Hi Tune processing that is added to the mix is determined by the Process Depth control.