I need level control moved upstream in the chain so that it's before my bass management controller. Has anyone had any experience using a passive control with the Zen?

I use a passive with my 2 Zen´s(running mono)and I´m never going back to active Maybe But you really need to think about buffering the CD from the Zen input´s. If you run a cd directly into the Zen even through a pot it puts a lot of strain on the cd´s OP. The Cd likes to see a high OHM load to run into that make driving of the output amps on the cd do less work. The power amp ,that would be the Zen, Likes the least resistance of the signal coming into it. Hence the need for a buffer in between source and amp, like a Zbox or in my case a MF10d tube buffer. There are a lot of chip buffers out there but if you can use tubes then why bother But then Maybe youre pvc has some kind of buffer?