My informal study of this has indicated that nobody has EVER had an issue with transformers being disturbed by 6550 to KT120 to KT150 swapping. Nobody. My relatively modest Jolida 502P came with 6550s, ran 120s for 3 years, and now uses 150s for over a year…sounds brilliant, works beautifully with no noticeable transformer heating, and it’s buzzless. I, of course, noticed the warnings about current draw hazards but the Jolida dudes told me not to worry…so I don’t. I do use a PS Audio Humbuster III but mostly since another amp (SS for occasional outdoor speaker driving) I plug into the thing had a transformer hum at times and the Humbuster has 2 outlets. This could be a first for my informal study but somehow I doubt it. I’m staying tuned!
