This is bullshit. The HD800S is a rather light load (150 Ohm impedance) and just needs more voltage than headphones with lower impedance for the same SPL. As long as the amp delivers it's fine. I think the reason SBAF recommends tube based amps is that they want to compensate the HD800s peak in the frequency response at 6 kHz by an amp with a "warm" (falling?) frequency response. This cannot and will not work. Our member
@solderdude offers passive filters to fix it, on his
website.
I own a HD800 and before I bought it I tested it with an expensive headphone amp. I bought it and expected that I might need to invest into such a headphone amp because I had read similar stories about it. Therefore I was very astonished when I found out that the HD800 sounded better than
any of my other headphones (HD580, DT990) on
every headphone output I tried it, including my smartphone (Samsung S5 neo). So I safely put those stories into the
urban myths drawer.
There is only one headphone amp at this price point which makes sense to upgrade to, but only due to its vast range of capabilities (EQ, tone controls, adjustable cross feed, adjustable loudness, ...): the RME ADI-2 DAC. That this DAC/Amp is not even listed on the SBAF page tells enough.