Substituting a 5AS4A for a 5U4G OK?

[HWJ]

I have an old Sano amp that has a Sovtek 5U4G in it, and I have an RCA 5AS4A I'd like to replace it with. From what I gather on via searches, I can substitute it, but just want to make sure.

The amp schematic is here
http://www.schematicheaven.com/bargainb ... 50_WRT.pdf

[zaphod_phil]

I checked the schematic and this amp seems to have no relationship to the Marshall 18W. Therefore it is OT for 18watt.com, as stated on this site's home page. Unfortunately, I don't know the answer to your question either.