I’m surprised in this thread and some others no mention is made of Sola ferroresonant transformers.
https://solahevidutysales.com/mcr_portable_series_power_conditioner.htmThey’re not sexy looking, they’re heavy, they buzz, they naturally run hot, they’re not cheap and they’re hard to find (mostly because they’re made to order).
In spite of their drawbacks, not many other AC line conditioners do as much with so few components as a Sola. No semiconductors of any kind. No sacrificial MOV either, no need.
And yeah, I’ve used a MCR series for years and would not consider anything else. And yeah, it lives in another room where I can’t hear it buzz.