What I find funny though is that most people worry (and/or claim) that everything above -100dB is potentially audible (especially in DACs) and subsequently amplify those signals with amps that 'add' god knows what to their signals.

Pretty sure quite a few ppl on this forum have made that claim inc Marv, unless I misinterpreted his claim to be able to hear ~18 bits dynamic range? Not a jab, just sayin.....

I have no idea what my audible threshold is so can't say either way practically speaking , although the engineer in me is naturally bias towards less distortion...

What I find funny though is that most people worry (and/or claim) that everything above -100dB is potentially audible (especially in DACs) and subsequently amplify those signals with amps that 'add' god knows what to their signals.

This is probably one of the most harmful things that came from nwavguy. Misunderstandings or obsessive focus from laymen and sadly "engineers" (or other self-appointed experts who cite various unrelated credentials) on getting the best results from a suite of five or six measurements. Results that far far surpass what these very same people can actually hear.

Willing to bet that NO relation to subjective reports will ever be found though.

I would say there is quite a bit of correlation - if and only if you know what specifically to listen for*. For the EC Studio, Craig and I, and to a lesser extent Anaxilus, went through almost a dozen interstage transformers. We listened and measured (the transformers). It's no accident that the best of the bunch had the best distortion characteristics - mainly in the bass - where distortion tends to be highest and most audible.

However, the notion that distortion on a FFT spectrum plot is the end-all-be-all is completely ridiculous. We simply need to do a thought exercise:

The distortion of transducers is a magnitude or two (or three) higher than that of amplifiers. A headphone's distortion will completely dominate a amp's distortion on an FFT spectrum plot. If one wanted to be a hard-ass and "objective" about measurements, then amp distortion measurements (at least from most amps) really don't matter. If one wanted to be true to measurements, one cannot cherry pick ... it should be that the measurements that matter most are those coming out from the transducer as part of the total system.

*I've always maintained that measurements must be correlated to subjective experience and not be considered in a vacuum - measurements for measurement's sake. Jason @ Schiit said the same thing in his measurements post on HF.

Vali (hybrid amp) bass distortion. Same conditions. 20Hz and 40Hz for comparison.

For the 20Hz tone, Vali is slightly worse in 2nd order, but much better for 3rd order compared to The Studio. Same situation for the 40Hz tone, although 2nd order on the Studio is significantly better -65db vs -54db (Vali). Vali does have much lower 3rd order, about 33db better!

Succinctly, The Studio does have better 2nd order performance than the Vali, but is worse in the higher order distortions.

Holy crap, that's brave, posting 20Hz measurements out of a transformer-coupled tube amp! Transformers are most disadvantaged in the bass (just check some bad transformer-coupled designs for bass distortion, holy moly.) The Studio is daaaaammmmnnnn impressive.

I expect midband measurements to be really amazing.

From what I remember on the Torpedo measurements (which is not the same as the Vali and the Studio), different tubes had indeed different characteristics. The 6J6Ws had less overall distortion than the E90CCs, but a little more higher order distortion in the upper frequencies.

I would expect similar in other systems. However, obviously is not always possible to tube roll.

Also, those are indeed fairly good measurements for the Studio given the Vali reference, which I don't think uses transformers in the topology.