VTL Tetrode/Triode

Exactly right. I got over the 'unsettling'. The 'useful' remains.

What is the difference between the on/off rocker switch and the on/off rotary switch used on VTL amps? Which is the newer design? Thanks

If I'm not mistaken, the knob is only used on the double-decker Reference amps, the rocker on the single-deck Signature models and below. I would assume that the rotary switch is heavier duty rated for the higher power; maybe it's a 20 amp part. But I don't know this, and I suppose it could also just be a cosmetic difference. I don't think I recall them always using it on those models, but that observation doesn't prove anything, as they might have recently upgraded the part, just as they've upgraded their fusing in recent years. Call and ask. BTW, VTL has recently upgraded the input stage on the Signature monoblocks to a differential design as in the Ref's, but haven't seemed to advertise the change or its benefits. (Unfortunately, for owners of previous-gen Sig's like me, there is no upgrade retrofit possible.)

I'm not sure whether or not the upgrade of the input stage to the differential design has any sonic benefits IF one's cabling is all unbalanced, single-ended, with conventional RCA connectors. But it does make a difference if you're running balanced components with XLR connectors (or so I've been told).

Anyway, with my setup, which is unbalanced, it probably doesn't matter. (And in my system, unbalanced actually sounds better, there is more of a texture to the music, whereas balanced conveys a more bland, "bleached-out," sound. I gleaned this from having compared Transparent super unbalanced to Transparent ultra balanced - - but this was, of course, with the old input stage).

I agree that running XLR into the previous gen VTL amps sounds no better, and maybe just a tad worse than running RCA, even if the preamp is fully-balanced. It has been my experience that between true-balanced components, running XLR usually does sound better - certainly no worse - and I would expect this to hold true for the new VTL's.

It is possible to design a balanced input stage that does benefit from lower noise and distortion even if an unbalanced input is used on the RCA jacks. Converting a single-ended input to balanced before amplifying (not needed for the XLR jacks) can still lower both internally-generated noise, and even to some degree noise picked up by the interconnect, depending on its configuration, although this may not be as effective as if a balanced connection is used. I believe this advantage applies in the case of the new VTL input stage design. It did not apply in the case of the previous gen VTL's XLR jacks, which were included only for the sake of convenience.