I've thought about a TVC or a resistive passive attenuator as an alternative to my tube pre, and I will probably get around to trying one soon. As related experience, I've tried several active and passive analog output stages inside my modded CDP, including, most recently, two varieties of high-end silver 1:2 step-up transformers and a battery-powered 1:1 SS buffer. The preamp & transformer specs would indicate that the transformer alone should have an easy time driving short cables into the benign 100K input impedance presented by the tube pre. And indeed the passive transformer output alone does sound gloriously natural, smooth & detailed. But nearly all of the transformer's strengths are are retained, and dynamics, linearity, and LF control are significantly enhanced, by adding a very simple SS buffer circuit at the CDP output. So I will probably end up building a TVC like the Bent Audio or the Audio Consulting Silver Rock kit, and trying it both ways with and without a battery-powered buffer circuit. Bottom line, even with adequate gain at the source and good impedance matching, one can probably benefit from adding current drive of an active buffer.
