I’m going to add both of these mods in and wanted to see what people had for suggestions on starting values:

Mod 1 – HPF

For C1, BOM seems like most builds call for a 100N cap – the mod looks like it switches another cap in parallel to C1. I’ll probably use an on/off/on switch so I get 3 options. I thought about using a 47N as C1, with the switch adding either another 47N or 100N – so 3 options are 47N, 94N & 147N. Is it correct that as I increase the value on the input cap, I’ll be lowering the frequency of the filter, so I’ll get a lower frequency response? When I’ve breadboarded circuits, increasing that first filter cap has let more bottom end into the circuit.

Mod 2- HPF

BOM C2 calls for a 470p – 560p, the Klingon build documented using a 1N and a 10N on the switch. Is that an effective solution, or is the 10N going to be sucking a ton of HF content out? Is it correct that as I increase the capacitance in a HPF, I’ll be rolling off more HF content?

I’m an audio engineer by trade, so I’d love to just be able to calculate the crossover point in hz. I found these calculators for LPF and HPF’s, but I’m not entirely sure what comprises the filter in the schematic.

https://www.trance-cat.com/electrical-circuit-calculators/en/

Any tips would be appreciated. I’m just going to socket them now, but I’d like to learn the basics of filter construction so I can figure out these crossovers.

One other question – on the Muff’n PCB it’s got a screen for D7 that’s not listed in the BOM, schematic shows it as reverse polarity protection. Is something like a 1N4001 ok for that?

Thanks