Vinyl on NAD M10 lower volume

Ditto to adding an outboard DAC! Why bother because it will still have a different voltage output compared to streaming. The DAC in the M10 is excellent and adding a new DAC is a sideways move at best - and a waste of money!

It all depends on the output of your phono cartridge and the amount of gain in your phono pre-amp. A cartridge with higher output, or a phono stage with more gain, will increase the relative volume when you play LPs.

Thanks both for your response. You seem not to agree. 

Youtuber Tarun (A British Audophile) (see https://www.youtube.com/watch?v=X562tyZPgRQ&t=8s) pointed out that this might have something to do with the analogue input on the M10, which he thinks is mediocre. 

He believes it might be caused by the analogue to digital conversion in the M10. Therefore I thought an external ADC (so not a DAC but other way around) would maybe help. 

I would then still make use of the DAC inside the M10, but the input will be digital instead of analogue. 

What I was thinking is connecting the phono preamp to an external ADC converter and then connecting this to the digital input of the M10. Do you guys think this is worth looking into?

As this is a hassle with unclear results I would much prefer do something 'simple' as upgrading the preamp/phono stage. Any tips on beter preamps then the Rega fono mini? 

You really don't have any problem - the position of the volume control is irrelevant. Your sources simply have different output levels.

+1 cleeds! Well stated!