What source are you using?
Is it possible your DAC (or some other device) has it levels set at maybe minus 40 (or some other number) meaning you have to crank the volume on your amp?
My DAC is set at minus 15 meaning my Amps volume is set at about the 11 O’clock position. Please review your source to help you determine what is going on.
The volume control taper (how much output at a given position) can differ from manufacturer to manufacturer and this has nothing to do with how much output the amp is capable of delivering and the level of distortion at that level. A control that requires you to use a lot of its range of travel will be more easy to make small changes.
What streaming service are you using? Are you using an app on your phone or tablet/ iPad to operate the built in streamer? The reason I ask, is my streamer is a Bluesound Node. I use Qobuz. Thru the app on my phone, there is volume control. I’m not familiar with the Niam , but is that a possibility?
@rolling18, This is a guess so it is time to experiment.
I suggest you use the Naim as an integrated amp (remove Vitus amp) and disconnect the Vitus and see what happens to the volume control.
Does using the Naim as as integrated amp only make any volume control impact?
If given a choice between setting volume via the amp or the streaming source, do it via the amp, with the streamer set at maximum volume. This will ensure that the volume is not being set digitally by throwing away data. As long as you can get to the highest volume levels you want, your volume control range and how high you have to turn the knob ia not an issue.