Would I be wasting my money to get a turntable?

From a technical perspective the question here is does the amplifier have an internal analog to digital converter which takes the analog signal in the preamp stage and converts it to digital and outputs the digital signal.

  Amplifiers can have digital power stages and the common designation for this is Class D amps.  However, if fed an analog signal, which is then amplified, that isn’t the same thing as as changing an analog source to a digital source.

  I don’t know enough about the NAD amp to answer the first question but I have heard of amps that do place the analog signal in the digital domain.  If indeed that is the case with the NAD then I think the OP has asked a fascinating question .  And as other posters have indicated it will still probably sound very good.  As a practical matter if he has a large collection of LPs that he wants to play.  If the answer is no, and he is starting from scratch, I would stick with streaming or CDs, because it’s all going to end up as a digital waveform 

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.