I have a few headphone amps; some for clarity and details (THX789, Topping A90, ...) and some for richness and warmth - including class A ones (RebelAmp), OTL tube amps (DarkVoice) and hybrids (SMSL T1, Loxjie P20). This MT602 is a very nice addition to the collection. It provides a nice tuby warmth with some smoothness but does not loose in clarity and punchiness. Despite its very small size, the amp is very powerful and drives some demanding headphones quite well. As a hybrid, it is also quite nice for my planar headphones. It works also very well as a pre-amp in the chain. The build feels like quality. In total, the amp is absolutely worth its price.
I exchanged the two Chinese 6J1 tubes (which are not bad) with GE5654s and VOSKHOD 6J1P-EVs. I prefer the Voskhod ones since I feel the bass is more defined with them. Only small issue is that the switch-on delay is not working equally on both channels.