I use Aguilar OBP-3 preamp. Its treble frequency is at 6,5 kHz. What I don't like is that cutting the active tone knob does not tame the highs as I would like to. Do you think it would be possible to add the passive tone knob with capacitor to the end pair of wires after the active circuit, the same way as you would do with output wires after volume pot in passive bass? I am not any electronic expert, it is just a thought. Would that work or are there any catches?