Today I went to Sur la Table
again and brought my double basket with me to run a test case. I first pulled a double shot on the store model Breville Barista 860XL, and then did the same with the double basket that I brought with me. Both times, the pressure gauge failed to get into the optimal range, resulting in underextraction with both baskets. So I guess I'm at a loss. Cranked the burr grinder to its finest setting and that didn't change anything... the taste wasn't terrible but the crema dissipated rather quickly (within 20-30 seconds). So I'm bewildered as to why the machine can't get enough pressure over the double basket vs the single basket (the single basket gets the needle right where I want it every time).
If you watch the vid here, this guy is basically doing almost exactly what I do, using the same machine and double basket: http://www.youtube.com/watch?v=i4nBUhcDi3Y
In this vid he pulls a 40 sec shot and the pressure, flow, and color are all ideal...
I may need to work harder on my dosing (he used 25g) and tamping technique ... wonder if the beans he uses has a large impact?