Let's be frank, we don't deny that the design of HA-1AMK2 has some practical issues. We want to deliver a transformer-coupled all-tube headphone amplifier with minimum footprint and easily blend into a study desk with books and computers cramping together. The upright form factor satisfied the foot-print requirements but we have to place the circuit board immediately above the transformers. The placement of the components also provides less shielding than other conventional tube amplifiers. This explained point (3) from
@Twizzleshnizzle. Overall speaking, you need to be more cautious in setting up the HA-1AMK2 in order to achieve a silent playback.
On the other hand, a fully covered design allows you to use the amplifier in a tight space, without worrying that you'll touch the tubes accidentally, or even placed books or assorted study accessories right next to the amplifier. Unfortunately, that means you need to remove the case in order to perform tube rolling, as Twizzleshnizzle has stated in point (1). If you only roll the tubes occasionally and settled with your choice of tubes for a while after rolling, this design is acceptable. However, if you are a frequent tube roller, then this is not a good design for you.
