I have a GRAAF GM50B INTEGRATED AMP. I would like to fit a set of cryod TUNG-SOL KT120 Tubes to the Amp. Can this be done without damaging the amp. The TUNG-SOL KT120 has a rated 60W power output. The filament draws a little more current than the KT88s. Will this extra current take out the GRAAFS power transformer. The GRAAF has 50+50W RMS power output.