Click on these URL's for some interesting information regarding the 6146X series. Very good reading. Mike(y) W3SLK http://home.comcast.net/~k9sth/The_6146_Family_of_Tubes_1.htm http://frank.pocnet.net/sheets/049/6/6293.pdf http://frank.pocnet.net/sheets/049/6/6146W.pdf http://frank.pocnet.net/sheets/079/6/6146B.pdf http://frank.pocnet.net/sheets/049/6/6146.pdf