The 6922 is rated for 220V Anode Voltage (absolute max):
https://frank.pocnet.net/sheets/049/6/6922.pdf
The Russian 6N23 which is often sold as “6922” is rated 300V Anode Voltage:
http://www.goldenmiddle.com/files/6N23P.pdf
The 5670W (which our adapter re-pins for 6922 pinout) is rated for 300V Anode Voltage (absolute max):
http://www.r-type.org/pdfs/5670WA.pdf
None of these tubes should be used with 400V Anode Voltage. It may work, but it severely exceeds the manufacturer’s absolute limits.
The 5670 has a higher rated anode voltage than 6922 and matches 6N23. So in any equipment correctly designed to use 6922 valves, it will work fine.
In this case, only use manufacturer-supplied valves which have been tested to withstand these above absolute maximum rating conditions.
