Interesting rollo! Do you remember what tubes your buddy's Aikido was running?? It uses coupling caps on the output, so those will obviously have an effect on the sound, proportional to the budget.
I have not heard a TVC yet, other than the Russound inwall unit for my patio speakers
My amps have high input impedance so TVC should work well. I already have the Aikido boards, one for octals and one for niners, so that project is inevitable. I was planning to make a
Lightspeed type attenuator with the LDRs from
Silonex. And use battery power or a couple Hynes regulators to power the Aikido. I hope to have that project done by years end. Lots of DIY projects on the list for this coming year...