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Master Volume for Active Tube Crossover?

I know this isn't a tube amp question, but I didn't know where else to put this post. I've given up on passive crossovers. Having to use massive inductors and caps to obtain low crossover points is no fun. Active tube crossovers are the way to go. Being a bit of a newbie on the subject, I've been checking out Tube Cad and and Steve Bench's website to come up with a decent design. Both sections are L-R. The low pass is 4th order and thev high-pass is 2nd order. (see schematic).

My question is; what would be the best way to include a master volume for both sections that will not weigh down the high impedance at the input, or change the crossover frequency by adding extra resistance to the first section of the low-pass filter.

Thank you,



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