I'm not an 'expert" by any means...just a regular user of vacpots over the last 3 or so years
FWIW, if you have a smooth-top electric stove, then you do not need to use a diffuser. I have used my little 20oz 5 cup Yama without any problems at all. I also collect usable vacpots from the '30's - 50's, and use the same stove with them. ...
Gary
My prep:
^ 5 "cup" level, runs just a hair over 22 oz (.65 L)
^ 45g of PNG Kimel Peaberry
^ grind level, very fine pour over
NB: Most important ingredient - water, needs to be Wisconsin spring water
Heat diffuser is not needed on gas. I used it with a clean and rinsed (and very important - dry) coffee base.
Technique - needs some work
^ 22 ounces of water in base. Electric stove on Med plus (6.5 out of 10)
^ At 7:00 minutes, water began moving to top (dropped stove to Med - 5 out of 10)
^ Water on bottom began boiling and whooooooooooooosh, water moved to top. Stirred bloom once.
^ B|Java panicked and immediately moved burner to Low, 2 out of 10
^ Bad move, a hair of water remains so pot was safe
^ Moving it to low caused vacuum to break and whooooooooooosh, water went to base at 8:30
Cup:
^ Tad underextracted by my tastes
^ Delicate, maybe refined catches it better?
^ Very clean, but not squeaky clean
^ Accentuates aspects of a cup
The PNG's marmalade exploded midway through the cup. The cup seemed brighter than my usual KMB or Bodum pourover. Too bright and fruity for the Czarina ... she apologized. Very Midwestern bride (Scandihoovian roots).
Next run will be:
^ Put coffee in after the water is moving north more rapidly. I think it pulled out acids and tons of caffeine at lower temps.
^ Leave the burner at medium for a 120 second extraction.
Mechanics:
^ I have chaffy coffee from the Gene Cafe. It appeared in the cup, along with some sludge, not unlike a press pot. I may need to look at how I placed the filter in the pot, making sure it is a bit tighter.
Thoughts:
^ Delightful prep
^ Very tactile, hands on style - sensory ladened
^ Will be fun to see what the unit does with different aspects of origins
^ Will take the pot into the kitchen supply outfit in town and have them suggest a brush (vase brush?) to help rinse out the pot.
Would I buy it again? Does the Episcopal church have problems? Did the Dodgers play in Brooklyn? Is Peter an old, stubborn German?
Great fun.
B|Java
[Pics below, as I took my first run at the Yama this morning.]
1) Yama with Navy cup for comparison
2) Yama meets Kenmore (Irish and Hoklo 福佬 greetings exchanged)
3) Yama gets baptised
4) Retro colors for retro pot - "Whoosh"