KT77 and 6550 will work,
Tungsol 6l6gc big bottle, has a lot of bass response
Tungsol 6550, warm sounding tube with ample bass response
GL KT88- one of the best i have tried, bass response is tight, highs are extended but not too ear piercing
JJ E34L - Warmer than the JJ EL34, bass is response is very good.
This was on a Cayin A-70T
Anyone tried using different tubes (Besides KT88 and El34) for the CS-55A ? Possible daw KT77 or 6550 based on another thread? Thanks