The coffee is sour, is there any way to solve it?

In fact, most coffee has sour ingredients, such as common coffee, we say that Colombia will have a "bright sour" taste, some African coffee will have fruit sour taste and so on. If you do not understand the sour taste of coffee and think that there will be no such taste in coffee, then once you taste the sour taste, you will feel very surprised, which subjectively magnifies the degree of this acid.

The description of taste varies from person to person, but the sour taste of high-quality coffee is not offensive. What you said in the problem description tastes "very sour" and seems to have reached an unacceptable level, so I'll take it as shoddy acid. There may be several reasons:

1. The baking degree of beans is too shallow, maybe the baker's preference for acidity is more than you can bear, or it may be that the baking itself failed.

2. Coffee beans have been kept for too long. They have been kept for a long time before they are sold or long after you buy them back. The expired beans will show signs of sour.

3. The degree of grinding is too coarse, which results in insufficient extraction and sour taste in the process of making coffee.

4. The water temperature is too low (but you say it is American, American coffee machine generally does not have the phenomenon of too low water temperature)

5. Let the coffee cool after making it, and the cold coffee will highlight the sour taste of the coffee

6. Cool after adding sugar, which highlights the sour taste.