Coffee experts - espresso advice please!

[housemum]

I have a Delonghi coffee maker, the "Magnifica" bean to cup machine. Recently, I've found that the espresso is tasting bitter - is this something I'm doing wrong, or that I'm using the wrong sort of beans? At the moment I have some Sainsburys TTD Colombian beans, but there is a really bitter aftertaste. I'm sure that when the machine was new it was never like that, the first couple of bags of beans were from Whittards then we just bought in the supermarket. Any help appreciated (unless it's buy £15-a-bag beans, can't stretch to that I'm afraid)!

Not an expert on espresso machines, but I do notice that two things give me bitter coffee in the press: the longer I leave the coffee to sit before I push the filter down, the more bitter it is, and also if the filter on the press hasn't been cleaned properly by DP who never washes it out, it's also more bitter.

By analogy, could you shorten the brewing time that the water is going through the ground coffee? Or make sure there isn't some old residue in the machine somewhere that's making it bitter?

Actually I've just found this which may be more useful to you. It seems to confirm my brewing time and cleaning guesses but also gives a number of other ideas which you may find helpful.

Some good ideas on there - one might be the stale beans, perhaps I should be going to whittards rather than sainsburys. Will give it a thorough deep clean and descale first in case that helps.