Would I be wasting my money to get a turntable?

Perhaps the Sugar Cube example provides insight into this question.  A Sugar Cube is a gadget that removes clicks and pops from scratchy or otherwise noisy records.  It does this by making an instantaneous copy of the music digitally, automatically editing out the noise, and then allowing the cleaned up signal to be amplified and played.  The user can compare before and after to hear what the effect is both of the noise reduction and of digitization of the musical signal.  It is so effective that many users simply leave it on full time.  In other words the digitization of analog signals as a serious degradation of purity is greatly exaggerated.  There is no reason for you to deny your desire to add a turntable and records to the enjoyment of your hobby.

@carlsbad2 + 1

So, this thing takes an analog signal, digitizes it, then converts it back to analog?

Why?

The basic answer is ’energy efficiency’ - by converting the (voltage amplified) signal into a PWM (or other modulation technique) signal, and then filtering that PWM to retrieve the audio signal, the transistors in the final stage are always ’open’ or ’closed’, thus dissipating minimal energy.

Note that in many power amps the analogue-to-digital conversion happens only at the final power stage, which is where ’traditional’ amps consume most energy, however the NAD seems to convert phono signals to digital earlier than that.

Digitizing itself isn’t going to kill the vinyl sound; I’ve had quite good results with Meridian 808i DAC / preamp units that digitize all analog inputs input and apply DAC / filtering on output - even with very high end vinyl gear. It can be suprisingly transparent. The main thing is that if you're used to a tube preamp, you won't get its added warmth and fullness from any digital preamps (as line stages they are a bit clean and dry) - though you COULD pipe the digital preamp into an input of a tube preamp...

That said, I also had the NAD M12 digital preamp and did not like its sound, at all. The M22 amp was fine, but the M12 did not make the cut here - I think even their older M51 DAC might have been better.