THE SHORT ANSWER
Unpleasant bitterness can come from roast style, uneven or excessive extraction, dirty equipment or an overly concentrated recipe. There is no single cause. Start with a clean brewer, then change one brewing variable at a time.
Name what you taste
Roasty, smoky, drying and harsh are different sensations. Try the coffee once it has cooled a little so heat does not blur your judgement. If it tastes balanced but simply too powerful, a small splash of hot water may help you separate concentration from flavour balance.
Start with the easy checks
Wash the parts that touch coffee according to the manufacturer’s instructions. Old coffee oils can follow you into a fresh bag. Check the dose and water measurement, then look at the flow. Baratza’s espresso guidance suggests trying a coarser grind when a shot is bitter and slow, but the whole recipe still matters.
Change the route if needed
If small recipe adjustments cannot give you the cup you want, try a different roast rather than fighting the same bag forever. Keep a short note: bean, dose, water, grind and one tasting sentence. That turns an irritating morning into useful information for tomorrow without buying a new machine as your first move.
Change one thing, taste, and keep a short note. A recipe becomes useful when you can repeat the cup you enjoy.
Try it for yourself
Sources & further reading
Source links support the factual context. Our home recipes and tasting suggestions are identified as starting points.