One more question — if there was channelling, would that necessarily be seen in the puck? The reason I ask is that I use a 9Barista, and the design of the 9Barista is such that I don’t see the whole base of the portafilter as the extraction occurs, so if channelling is happening towards the circumference of the puck, I may not see it.
The espressos I get are uniformly good to excellent, so again, this might be in the category of things I don’t have to worry about. It does lead to another interesting question — if there’s channelling, and the espresso tastes great, did the channelling actually happen? 😉