The designer/manufacturer of the AM Audio 833S Ultima wrote to me that he will add an unbalancing transformer inside the amplifiers.
Do you have any recommendation for the highest sound quality unbalancing transformer I could perhaps specify for him?
Finemet from Hitachi Metals would be your best, if you can get them in there. These are the best signal transformers on the planet, but not cheap. Expect to pay more than double vs. Lundahl or Sowter.