Thanks for taking the time to reply. It shocked me slightly ...
Having been brought up to always ensure that audio sources earlier in the audio chain are at their strongest signal this concept seemed very strange to me. If the second amp in the line is amplifying a "weak" signal as loud as it possibly can wouldn't this produce poor sound quality or at least negatively affect the sound by some margin?
After a little more reading around pre-amps/power-amps tonight I totally see the point you are making but doesn't the presence of two pre-amps (one in the M-DAC and the other in the headphone amplifier) create my perceived problem? Particularly as the second pre-amp is set to max gain.
Once I receive one of the amps (hopefully this week) I will certainly test this myself anyway and I really hope you're right and I can't hear the difference
. I would be delighted if I could use the remote on the DAC as I can't quite reach the amp from my chill out recliner!
I've obviously got a lot to learn about amplification and how it all works.
Thanks again for the reply.