Running DCS Vivladi DIRECT?

Sorry, but you're confused.

If you keep the volume on the Vivaldi between -9-14dB for a -20dBFS signal, the volume level on the Vivaldi will still be at -9-14dB for a 0dBFS peak signal. The attenuation level stays constant irrespective of the source's signal amplitude, the same attenuation level is applied to a -20dBFS signal and a 0dBFS signal.

-20dBFS signal + 9dB attenuation = -29dBFS signal
   0dBFS signal + 9dB attenuation =   -9dBFS signal

So you always listen at -9-14dBFS peak levels.

Keeping the volume between -9-14dB on the Vivaldi for the 0.6V setting means the output level is too high.

@seigen please read page 14 of the Vivaldi DAC manual, -10dB is dCS’ highest recommended level for direct connection
https://www.dcsltd.co.uk/wp-content/uploads/2015/06/Vivaldi-DAC-Manual-v2_0x.pdf

Yes, to have some range to go louder above the "comfortable listening level", but if the max SPL you listen to has the volume control always set at -9-14dB then the 0.6V output is too hot.

Here’s another way to look at it, maybe this way you’ll get it:

0.6V @ 0dBFS = -2.21 dBu
0.2V @ 0dBFS = -11.76 dBu

Now apply 9dB of digital attenuation to the 0.6V signal, you get:

-2.21dBu - 9dB = -11.21dBu = 0.21V

So whether you use the 0.6V (with 9dB of digital attenuation applied) or the 0.2V (with no digital attenuation) output setting, the DAC outputs the same voltage basically at 0dBFS.

Fine -- and when I change my phono stage and drop from 45dB gain to 40dB the 0.2V may also be a better match than the 0.6mV

But still no explanation of why the direct connection does such a relatively worse job of handling dynamic range (if we put all the soundstage stuff down to coloration, which btw I wholeheartedly do not) -- and no it’s nothing to do with the -9dB cut as the dCS volume control is digital and non bit stripping