Jadis Orchestra Reference ---- tube biasing

I own a jadis orchestra reference, I replaced my tubes 6ca7 to KT90's. I asked jadis to what tube to use for my amplifier. As far as they said as long as you made your biases for tubes (it's manual and you have to take off the bottom cover and measure the voltage on potentiometer) it's a hard job and you have to do that every time you change tubes if not you could blown your transformers. So biasing manually is must, be carefull on changing the tube types.
Regards