My filters are made to work in the effects loop as well as into the input. They can take higher voltage if more headroom is needed, but so far I don't think anyone has reported needing to do that.
Your inbox is full! We can't even send a message to buy your pedals! You are about to get 400 more orders just from this posting about your pedals..
Anyway, We need to talk. I think I need your LPF! I want all the highs gone from my speaker!
I'm the guy that pays $100 for 3-foot Gold cables because I want to believe it makes the sound better! You will want my money.
Clear your inbox! haha.