(!!!!!) (Best Overall Single) CK-5687WB Raytheon black plates NOS 1960's (40.5ma/42ma) (Audio Note, Modwright, Manley) Highest mA and Gm1 low noise tube) CK 5687WB Raytheon black plates NOS 1960's 1 section) 40. 5ma Gm=12,400 1 section) 42. 0ma Gm=12,700 Tested on Amplitrex Vplate=120V Vgrid= 2V Good Ma range 28 35ma Good Gm range = 10K 12K 7119 is best sub for a 5687 and visa versa Modwright preamp Audio Note DAC 4 Audio Note Jinro amp Audio Note L3 Audio Note M3, M7 preamp Manley Ray Samuels Raptor and B52 Aria VW5XL Modwright Sony DVP999ES Audion 845 Black Shadow Bottlehed Smack