Amplifiers that use adjustable fixed-bias should be checked and adjusted when changing power tubes. This will allow your amp's power section to function as designed, prolong the life of your tubes, and help your amp to sound as good as possible!
This testing and adjustment is done in a live circuit with dangerous voltages present, and should only be done by a qualified technician with the proper training and tools. It is quite possible to accidentally damage your amp, as well as cause yourself serious injury or death, due to DC voltage often exceeding 400V.
This testing and adjustment is done in a live circuit with dangerous voltages present, and should only be done by a qualified technician with the proper training and tools. It is quite possible to accidentally damage your amp, as well as cause yourself serious injury or death, due to DC voltage often exceeding 400V.
Amplifiers that use cathode-biased designs generally do not need any type of adjustment when changing power tubes.
Some people forgo the maintenance involved and simply swap their tubes without checking the bias. If your amp sounds good to you, it may be just fine, but the correct way to do it is to have the bias checked!