7f33ac1a_ecp_cc__Value_Notes
[Part] C4L, C4R [Size/#] 10.5mm case, 5mm pins [Value/Notes] 
These are power supply decoupling caps for the tube section. The value is not critical -- 100uF to 220uF is fine, but use what you like. 35V or better is recommended. Unlike solid state circuits, putting huge caps here won't add bass.
ecp.cc
Value/Notes