It started, as these things do, with someone giving me a good bag of beans for Christmas. Proper stuff, roast date on the bag and everything. I brewed it the way I brew everything and it tasted, well, fine. Which is the problem. Good beans should not taste fine.
So I did what any reasonable person does and blamed my equipment. My grinder is one of those whirring blade things that costs about a tenner and chops the beans into a chaotic mix of dust and gravel. The dust over-extracts and goes bitter, the gravel under-extracts and goes sour, and you get a cup that's somehow both at once and pretending to be neither.
The fix is a burr grinder, which crushes beans to a consistent size between two rotating surfaces instead of just attacking them with a propeller. I knew this in the abstract. What I didn't know was how deep the hole goes once you start reading. Flat burrs versus conical. Stepped versus stepless adjustment. Retention. Hand grinders that cost more than my first laptop.
I closed the tab before I did anything stupid, then opened it again an hour later and ordered a mid-range hand grinder. It arrived, I dialled it in over three increasingly caffeinated mornings, and the same beans now taste like the person who gave them to me clearly intended. Turns out the bottleneck was never the beans, and it was never the kettle. It was the bit in the middle I'd never thought about. Most bottlenecks are like that.