I have an MPG Level 5 with an Aguilar OBP-3 preamp in it. It has the stacked Treble/Bass knobs and a Push/Pull mid knob that is supposed to give me mid-frequency sweep (400Hz - 800Hz) and mid boost/cut. Can anybody explain to me how the Mid knob is supposed to work? I have tried to find instructions on Aguilar's website and searched the forums and not found it. The reason I am confused is that it does this: - Knob has a center detent whether it is pushed or pulled. - I start with it pushed in and centered on the detent. - I pull it out and it is at the center detent. I turn it fully clockwise. - I push it in and now, in the pushed in position, it is no longer on the center detent. It is also fully clockwise. This doesn't seem right.