This is my travel board of tone. I mainly stick to plugins for effects.
The Nano Cortex is there just so I can capture and share tones I have nailed down, to give me a few effects when need a little something, to give me headphones out, and to act as a digital interface. I still haven't decided if it is a keeper.
The Notaklön is there for tone and volume boost more so than distortion.
29 EUNA magic box of mystery.
The Enigmatic's tones and a thing of absolute beauty.
Don't sleep on the Lion's clean tones.
The Woodrow is just a cool vibe sometimes.
What’s the 29?
It's a buffer with a charge pump and three switches that drop different passive EQ filters into the circuit.
From what I can tell from the reverse engineered schematics it's a dual sided op-amp buffer (as opposed to something like a transistor based jfet buffer), kind of like what a klon uses, three passive tone filters built around dropping different cap/resistor combos into the circuit, an "effects loop" aka a buffer bypass for anything that misbehaves when the guitars output impedance is changed before the effect (range master, germanium fuzzes), and an overbuilt power section with an unusual amount of power filtering (there are so many electrolytic caps in this part).
I will not comment on whether I think it's worth the pricetag.
It might be placebo effect, but I just love how it makes my main guitar sound. Is it essential? No way. Most musicians have been playing just fine without it, but I had the means and I really wanted to support the builder.
I don't think it's a placebo effect. Buffers do a tangible thing. They set input impedance and increase the gain in a signal. Turning on a low or high pass filter does something tangible. Depending on how they're used/designed they'll cut frequencies, which gives the impression of emphasizing others. A charge pump changes the voltage in the circuit. I think this one gets bumped up to 15v (I could be wrong about that). Usually this gives the impression of headroom. If you've ever tried something like the Hudson broadcast, the charge pump in it is switchable from 9v to 27v - it's a huge change.
I probably should have mentioned that your original post calls this circuit magical and mysterious and I was partially responding to that. It's not. It looks over-engineered and I'm dubious that it does something that a different buffer or even an eq pedal couldn't do, but that's my own take. I don't think there's anything wrong with buying one. I have a ton of pedals. 80% of which are extremely redundant.
I have a Bognor Harlow that I think of that way. I don’t have it doing a lot, but it adds something ineffable to the sound, and I miss it when it’s not in my chain. I’ll definitely have a look at a video of this thing, it sounds intriguing at the least
The best way to understand the 29 EUNA is to watch some YouTube videos about it with headphones on.