Thanks. What baffles me is that the hum is always louder at the left channel even I swap right tube to the left.

Question regarding startup hum. My WA6 always has startup hum louder at left channel no matter how I swap/change tubes. It is not related to headphones as I have changed those as well. All hum does go away after 10 secs or so. WA6 does sound normal to me. Anyone here notices the same?

Anyone tried 5963 signal tubes with the amp?

Hi,   It seems to me that the change will no longer allow the swap of other previous compatible tubes such as 7N7 which was said to have superior sonic advantage.   

Has anyone tried 5963 with the HA-1A MK2?   My understanding is that the 5963 has lower maximum plate voltage than the 12AU7 but it is otherwise very similar.

Hi Andy,   My HA-1A MK2 also hisses and hums.   Having said that, I wonder what amount of hiss and hum are considered to be a problem.   With my less sensitive headphones, the hiss and hum are barely noticeable.     BTW, does the HA-1A MK2 has relay mute at start up?   The Chinese...