"We regret that the result of the coffee preparation has not yet met your taste. The decisive factors for the flavour of a coffee from an espresso pot are
Coffee type + grind + coffee quantity + water quality.
The appliance itself has no direct influence on the flavour or consistency. It brings the water to the boil until the resulting pressure forces it upwards through the grounds and collects in the coffee container.
We can therefore recommend that you experiment a little with the grind of the coffee (the finer it is, the longer the water takes to pass through, the more flavour particles - including bitter ones - are released). So use a slightly coarser powder. Do you grind the beans fresh yourself? Or do you buy pre-ground espresso powder? Then tell the shop what type of coffee machine you want the beans ground for. If necessary, also make sure that your coffee contains more Arabica beans than Robusta beans. Robusta is more bitter.
Or perhaps you have very hard water? This could also be a reason for the unpleasant flavour.
As you can see, there are several factors that are important for a good flavour. We very much hope that with the help of our tips you will be able to find and adjust the factors that are important to you."