Headonia 300B has an input voltage sensitivity quoted by the manufacturer as 1.8V SE and 1.6V balanced. So with your dCS DAC set for 6V then you are likely to be increasing distortion. This is particularly likely if you are listening to pop/rock produced over the recent years where average recorded levels of 0.0dBfs or thereabouts are almost constant.
This why I wrote " and what you consider bad" . Although not desirable from a purist viewpoint you might enjoy the result and it could be why you find the higher voltage subjectively sounds like it has more UMPH.
Agreed with all you say. However, @ARDDCS says that he has tried but prefers using 6V.
As it is his system I cannot argue with his choice should it be is his preference. it is an example of what I see as as a a split in the audiophile world around 40 years ago ( with The Absolute Sound magazine leading the way in the USA earlier) when seeking the most accurate reproduction was no longer the sole arbiter but , rather, “what I like” ( an opinion without supporting evidence) largely took over.
I am not able to see that it may result in any physical harm to the equipment ( unless anyone has further information,) so my view is let him enjoy if it is to his taste.
Thank you both. I appreciate your taking the time to respond. After some more listening and reading I have moved the DAC down to 2V from the 6V. Now to be honest I think I like the difference I hear between the two at the 6V That said , Stepping back and remembering the systems I have had over many decades I have been in the hobby you made a comment that got me thinking again. Thinking about expectations of sound. The stereophile comment is what I am referring to " what you like from what is right “(technically) and remembered I got into the hobby at this level exactly because I wanted to get to the purest most accurate reproduction I could afford! Over time forums, Audio shows and” You Tube videos" have contributed to sound expectations greatly IMHO, so much equipment with manufacturer marketing and influencer conversations have shaped much of the HP space for sure . Nothing wrong with listening preferences for sure, after all it’s your investment. But even in that case having equipment at the TOTL level still gives you the best jump off point to pursue your sound so have at it. That said I did spend time then trying to allow for reprogramming my brains expectation and are finding the 2v selection is not making me settle for Less SQ ,for a less dynamic presentation but rather just different, maybe a bit more finessed ? After a bit of listening it sounds just as cool, maybe more with a more optimum input Voltage setting.
I had a number of Amp’s. I am very satisfied and impressed with the 800B. I like many things about it , some nice functional touches like being able to visually track the total hours the amp is running, the hours by each individual tube, the Impedence selector switch. But bottom line would be it is masterfully handling the Susvara Unvailed connected to the Rossini Apex Player. IMO no small accomplishment. I’ve been through several amps to try and drive Susvara with no luck. The Headonia does to its full potential.