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The unused op-amp could have been put to good use as a rail splitter, I suppose.

I did, and got really really drunk 🤣

I forgot about the thermal camera, it's been a while since I used mine. Great troubshooting tool if you have one.

Did you ever have to find a power short circuit on a board with dozens, if not hundreds of little power decoupling caps all over the place? And they all look fine! How do you find the culprit? Wherever you measure across power, it's a dead short. Or is it? Not if you use a milliohm meter...

I actually prefer soldering (and desoldering!) SMD parts to through hole. With the right iron (I use old Metcals), tweezers and a magnifying glass lamp or goggles, it's a piece of cake. I'm 53 btw, with the usual eyesight issues, so it's not just a young person's game.

Here's a selection: https://www.digikey.ca/short/h3q4zrpj

100v rated X7* will work well just about anywhere in a pedal powered by 9 or 18V. They'll likely stay within +/-10% through any temperature change or voltage that a pedal is likely to see. Just don't use them where a tighter tolerance is needed (5% or less).

Circuits with PNP transistors usually use a positive ground because PNPs are biased the opposite way of NPNs: their base and collector need to be more negative than the emitter. Since the emitter is usually common between the input and output, we call that node the ground: the common potential...

I asked and she said she always prefers a hard cl ick. Whaaat? Did I make a typo?

Well, depending on what comes before, the extra noise may or may not make a practical difference. If it comes after some gainy pedals, then there might already be enough noise baked into the input signal that a bit more doesn't matter. But it's good to know that non-inverting is always less...

Only if you don't mind the major extra noise. Here's the difference between inverting and non-inverting unity gain buffers, both with a 1M input impedance:

Not sure why you're using an inverting configuration for the input buffer(s) (IC2). As shown on the schematic in post #3, your input Z is 50k (R13||R14), which is way too low if you're going to plug a guitar straight into BLEND_IN. Also, the buffer noise performance is significantly degraded...

It drops the 68V to 37.8V.

I thought about it, but I'd like it to be self-contained, power and all.

I really did not have this in mind when I made the little PCB, but it seems to fit in an inline 1/4" female Neutrik! How convenient. I did have to cut some PCB corners, no big deal. One tiny "detail" remains: how do I power the damn thing?? Use a TRS cable with the ring = +9V? Too convoluted.

C1 is there mostly as a placeholder. It can be left out or changed to a different value. As shown, at 100pF, it doesn't do very much, other than some protection against RF interference. It's the equivalent of around 3ft of guitar cable. Higher values would start making the sound darker/warmer...

I've seen this circuit floating around. It makes sense if you're designing an active pickup from scratch, where you have control over pickup parameters such as the inductance and output level of L1 and L2, and you might want to amplify the coils separately and maybe even load them differently...

I thought I'd share this simple but very well-performing inline buffer/booster. It's intended to go onboard, but nothing's stoping you from using it as part of some other circuit, pedal, whatever. I made it following a request from a European luthier who found a very good sounding, but lower...

Wow, I admire the lengths to which you went instead of just buying the Behringer - - one of the best products they've ever made. We have a couple of them at work and we've been using them for some 20 years. All you need is a piece of tape to cover the logo and it's golden. 😁

I'd consider ditching the FET and using the op amp non-inverting. You can add a pad after it to drop the level as needed for the codec. Non-inverting is always less noisy than inverting, and you also get the high input impedance.