Not much progress to report.. Got a little sidetracked - again.

I have done some work on the active filter. Most of the PCB's have been etched, and I have started soldering on the power supply.

I had to build a new Pre-amp in between. Similar modular approach as the active filter, with the same connector for the amplifier modules as the active filter has on the output modules. Actually the amplifier modules used in the pre-amp is borrowed from the active filter project.