... and, if they're only just a rectifier tube which you should only get from Woo:-
"Rectifier tubes upgrade 1:
Takatsuki TA-274B single $965 (1 pc) with 1-year warranty
Takatsuki 274B offer ultimate performance to any current production 274B's. Users have claimed that it exceeds the quality to NOS Western Electric 274B.
The TA-274B sold in an individual package Click to see details."
"Rectifier tube upgrade 2:
Sophia Princess Mesh Plate 274B rectifier $160 (1 pc) with 30-day warranty
To impact WA6's sound quality or for your super backup. Buy and ship independently.
Sophia Electricâ„¢ 274B tube is a premium rectifier tube for a 5U4/5R4/5AR4 direct replacement with 3X longer plate structure, thus it has a deeper, wider sound stage and even smoothier sound than Mullard 5AR4"
So, buy them up - and burn them out......
This,from the Woo site:-
"Everything Should Be Made as Simple as Possible, But Not Simpler - Albert Einstein"
Now you know why they don't bother with the 4.7M bias resistor......