I didn't downvote and I just got a new tube and it blows the detail and instrument separation compared to the A90D. Bass is harder and punchier and the Midrange is pushed forward so the vocals are just magical now. I got the SYLVANIA 6SN7GTB tube and it's been probably one of the most impressive experiences I have had in audio. Compared to the stock tube it's a complete night and day difference and I am actually contemplating selling the A90D. Anyways, I will write a follow up post tomorrow as I will get my 4.4 to 3.5 adaptor so I will also be able to use my 800S on there as I cba to deal with those hellish connectors!