I didn't even think about this being a factor in why my VAC preamp pairs so well with my Pass amp. I had attributed much of the synergy to the impedance match primarily but this makes a lot of sense.
Transformer coupled outputs/inputs in preamplifiers.
I have been a big fan of VAC preamplifiers, both for their musicality and their ability to optimally mate with all solid state and tube amplifiers I’ve owned. I believe this is strongly related to use of transformer coupling at output and input. Are there many any other tube preamplifier companies that use transformer coupled outputs (+/- input transformers). I am aware of the SE preamplifiers recently from BAT with transformer coupled outputs and a recent offering from Prima Luna, I believe. Any thoughts on these preamplifiers or others. Yes, I am aware that transformer coupling has its strengths and weaknesses, but I am convinced (after 15 years using VAC preamplifiers) that output transformers are generally the answer for compatibility issues. Thanks so much for all your kind input.