12-13-2013, 09:45 PM
On the 1U4 and 1R5, pin 1 is internally connected to pin 5, so no connection to 1 is needed if 5 is being used.
[Image: http://www.bunkerofdoom.com/tubes/syl43/.../1U4_1.gif]
[Image: http://www.bunkerofdoom.com/tubes/syl43/.../1U4_1.gif]