You say Raven Audio amp..What model do you have ??
I had Osprey for 5 years and was very happy but just months ago went with Reflection and I can not believe what my ears hear and have missed all these years in the music I have listened too..
I m running KT88’s and most of my music 90% sound beautiful but for the other music to sound good would need a tube roll probably to 6550 tubes..
If you can get them from Dave is Military 1970 6L6GC tubes these produced in Osprey the most amazing sound stage from that unit .But also 6414 talls in third row ,6060 yellows row 2 and Siemens ECC81 Row 1 ..The best sound that unit could produce..
The other power tubes I enjoyed was Tong Sol 5881 they had a warmer sound ..
Dave can find some really nice tubes for his product line.