Target bias dictated by amp or by tube?


If my amp's (Line Magnetic 508ia) manual says to adjust bias of each power tube to 120ma on the front meters, but a set of after market replacement tubes (Cossor Valve 508) state their bias should be set to 65ma, which stat should I be following when putting in the new tube?
divertiti

Showing 3 responses by divertiti

Appreciate the answer. If one were to use the lower of the two, which means it would be running out of spec according to the amp, does the amp simply produce less power or will the sonic qualities suffer as well?
@brotw The voltage should be dictated by the amp as only the amp designer knows what the real plate voltage is. Go 120ma my friend