Here's the GS-X Mk2 measurements: https://www.innerfidelity.com/images/HeadAmpGSXmk2.pdf Notice the dead flat FR response and incredibly low distortion. Tube amps can be tuned to be neutral, no doubt. But the tube amp being used makes the HD800 headphones sound "smooth" then that's a colouration. As well, no tube amp can approach the low levels of distortion compared to a well designed ss amp. Just the limitations with tubes....but the distortion introduced by tubes can certainly sound inviting (though definitely not transparent to the recording or more "neutral"). Nothing bright, harsh, nor glarey...feed it with a bright source, DAC or music and it will reveal what comes in. Play it with the HD800s (or other bright sounding headphones and amps like the 430 or GS-X Mk2), it will reveal them for what they are. Thus the "wire-with-gain" comments and Kevin Gilmore amps are very much like that (including the BHSE). In fact, when I compare the Abyss-Phi straight out of the DAVE or with the GS-X Mk2 in between them, the tonality doesn't change...just slightly improved control of the drivers yielding in a better perception of detail retrieval and control (though not night and day improved perception by any means). And to my ears, the DAVE is as neutral as any gear I've come across.