Dgarretson, I agree, it seems that TVCs have a number of advantages over straight passives. One of them is low output impedance, essential for interconnect control.
Kurt's approach optimizes the TVC approach, but at the price of his own admission, that you don't design for the real world. Having sources that have the ability to drive low impedances on their own really helps you with performance if you optimize the TVC for that.
Obviously, this approach is no good for production. In the 'real world' you have to accommodate the output impedance of a simple tube phono stage, which might be rather high. Its tricky to wind high impedances on the primary side while getting good bandwidth- in fact you can regard them as mutually exclusive.
On this account is why this is an on-going conversation that will likely never be solved. IMO its easier to build a high performance tube line section (we can reproduce a 10KHz square wave quite nicely too, and do a 20Hz square wave with no measurable tilt) than it is to get a transformer 'right', and still work with the real world.
Kurt's approach optimizes the TVC approach, but at the price of his own admission, that you don't design for the real world. Having sources that have the ability to drive low impedances on their own really helps you with performance if you optimize the TVC for that.
Obviously, this approach is no good for production. In the 'real world' you have to accommodate the output impedance of a simple tube phono stage, which might be rather high. Its tricky to wind high impedances on the primary side while getting good bandwidth- in fact you can regard them as mutually exclusive.
On this account is why this is an on-going conversation that will likely never be solved. IMO its easier to build a high performance tube line section (we can reproduce a 10KHz square wave quite nicely too, and do a 20Hz square wave with no measurable tilt) than it is to get a transformer 'right', and still work with the real world.