I believe the onboard pre in the ProIV is a Duncan BEQ-2 aka RBA-04M. There are Vol, Blend, Bass and Treble controls and there does not appear to be a push/pull switch on the Vol. I can't see a gain trimmer on the pre but then my eyesight is not what it used to be. Is there any way of adjusting the gain on the pre? I want to equalise the output somewhat between the Epi and my piezo bass which has a much higher output even with the preamp gain reduced as far as it will go.