It is known from switched mode PSUs that leakage currents are always present at the outputs, especially at ground. How does that work with these amplifiers?
The main problem with these toroidal transformers amps is the hum pickup, which can be seen in the poor thd+n readings in every test. Is there a way to shield it?
Maybe. If you have a DAC with double zero THD and one with triple zero THD, and a speaker with 5% THD, then you won't hear any difference. The speaker dominates.