After few hours of ‘burning in’ this is what I found.
The microphony of the tube is very tube dependent! I have bought two sets of the 5687 tubes by Tungsol and so far have experienced less ‘microphony’ in one than the other one!
Somehow AC heaters induces more hum, as such DC heating is more favourable.
I have stopped playing with it and waiting for the dual 50uF+50uF which was originally specified to arrived. There is this low AC humming which I suspect coming from the B+ voltage as I have used a substitute caps of 20uF instead of the 50uF originally specified. I was desperate and need to get it running before deciding to get the expensive stuffs or not. The dual cap was bought from ebay and could take anything form 7-14 days to arrive. Item was bought last week..