I've had the small one since 2011, bought from the factory. The Feima 800n and Bella Mini500 are pretty much the same machine except for the optional precision air valve. I've got the 800n.
Been to the showroom in Taipei and did a YouTube video on the EVO-1, which is a unique roaster in several ways; perforated cast iron drum and split gas trane with dual needle valves. There are three rows of burners that can be adjusted independently. The center row has one needle valve and the two outer rows another (both with gas gauges). You can run the center row, two outside rows, or all three rows. It's a lot easier to roast a small charge using only the center row.
The damper on these machines is probably better than anything I've seen so far, including variable speed blowers. Variable speed blowers are notoriously inconsistent, whereas a precision air valve combined with a fixed speed blower can easily replicate a setting. The dial on the air valve is cleverly done, with a 0 in the center position, minus to the left and plus to to the right. Sounds complicated but in actuality simplifies setting the air flow.
