Frequency-Interchange HPF

[eatkinola]

I've built the Frequency Interchange and would like to build a variant with just the HPF in a smaller always-on enclosure, e.g., similar to how that smaller version is made by Broughton. Looking at the schematic, I think I'd just need to cut out a few sections (shaded below). The first section looks like a simple opamp buffer (?), so I thought I'd keep that and just get rid of the LPF section and gain section. I'd eliminate one opamp and use the remaining for both the buffer and HPF sections. Does it look like I'm on the right track? I plan to breadboard it, but I don't have a way of verifying the HPF works (frequency analysis). I'd appreciate advice on this.

 

[jwin615]

Ditch LP1 all together
R4 can go.
I would keep an output buffer.
Need that block to keep the filter stable and set the output z. it doesn't have to be a gain stage, just a simple buffer like the first stage
FYI, this is a Sallen Key filter.