I'm curious and a bit confused about these as well. On the one hand these transformer based units seem to offer much the bonuses of passives, without the impedance issues of passives. On then other hand, some tube manufacturers are willing to deal with impedance issues to avoid using transformers. Some of those same manufacturers claim that transformers introduce phase issues. What's the real story?
TVC preamps: good or bad?
I was wondering what the advantages and disadvantages are of a TVC preamp? I have read elsewhere that transformers introduce coloration and aberrations in the frequency response, which is why we try to get them out of the output stage of valve amps. But ... what are the pros and cons of TVC preamps?