Hooking up sub to two different amps

This is Diyaudio after all! 😎

Install a SPDT switch to select LFE.

Screenshot 2023-02-28 at 00-25-19 Scheme-it Free Online Schematic and Diagramming Tool DigiKey...png


Better yet, use a DPDT switch to select LFE / low pass and control some relays to switch input from line level to speaker level.

Screenshot 2024-08-05 at 09-20-02 Scheme-it Free Online Schematic and Diagramming Tool DigiKey...png
 
The low pass filter, set to max is for LFE, but there is no detail as to whether this is just max frequency needed for optimum LFE, or an actual switch over to something else. Yeah, yeah. Always follow the manual.

I did hook up the tube amp using option 2 after unplugging the LFE in. At first, the sound was boomy, terrible. I saw that the frequency know was set low, around 80hz or so. I turned it up to 120 or so, and turned volume down a bit. Very good sound, low notes were distinguishable and volume was balanced.