A couple of thoughts... 1. ) check the filament voltage with the 6CA7 plugged in to make certain you are getting enough volts, as the 6CA7 draws more filament current. 2.) Try increasing the load on the tube by connecting an 8-ohm speaker to the 16-ohm tap. (The amp designer says this is OK to do.) Use your same bias. Also verify your bias voltage. 3.) Don't shock yourself.