Coffee, irregular

I am still experimenting with a new burr grinder and a coffee press. I don't have it down yet--and it's especially hard to judge now that I have run out of cream. I am not used to black coffee, so it is hard to say if I've done it right. I am certain that my coffee doesn't come close to Old Crown Roasters' consistently delicious brews.

A pourover brewer is en route. Maybe that will help.

Meanwhile--back to today's coffee. I've messed it up, somehow. The first few sips seemed okay--while it was still piping hot. After it cooled for just a minute or so, it became sour. Very nasty.

Googling "why does my coffee taste sour?" brought up top listing, faqs, which points to a site called Merlo Coffee. There it explains, "All coffee makers are designed to only be used for the maximum. I.e. no half plungers, no half stovetops!" (yikes... an exclamation point--danger) So, maybe that is my problem--I have been using a relatively large coffee press to make only a single cup of coffee. But I have gotten some decent results as well as some poor ones--so there must be more to it than press size.

Shrug. I am, for now, at a loss.