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NAD PP 4 Review (Digital Phono Stage)

amirm

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This is a review and detailed measurements of the NAD PP 4 Digital USB Pre-amplifier and phono stage. It was kindly sent to me by a member for testing and costs US $199 on Amazon including Prime shipping (retail price $229).

I like the compact form factor:

NAD PP 4 Digital Phono USB Preamp Review.jpg


The variable gain is nice to get the levels to be close to but not exceeding digital clipping. On the latter, it would have been nice to have an indicator.

Rear panel shows independent RCA inputs for MM, MC and Line input which is unusual:
NAD PP 4 Digital Phono USB Moving Coil Moving Magnet Stage Preamp Review.jpg


I don't know how old the unit is but the MC to MM switch had already gone partially bad causing one channel to cut out. My just need some lubrication.

NAD PP 4 Pre-amplifier Measurements
I started my testing using Line In:

NAD PP 4 Measurements Line In.png


Performance sadly is pretty low, struggling to get to the equivalent 14 bits, landing the PP 4 pretty low in rankings of ADCs/audio interfaces:
Best USB Phono Preamp.png



Worse yet is the phase mismatch between channels. I notice this right away. I wonder why whoever designed this for NAD did not catch this simple mistake.

Frequency response is good and it indicates 44.1 kHz sampling:

NAD PP 4 Measurements Frequency response Line In.png


IMD distortion versus level shows high noise floor (sloping down part of the curve):
NAD PP 4 IMD Measurements Line In.png


All of this sets the upper limit in performance of the phono stage.

NAD PP 4 Phono Stage Measurements
Let's start with our moving magnet dashboard as usual:

NAD PP 4 Measurements Moving Magnet.png


Ouch. We have a ton of distortion products on top of mains hum I could not lower resulting in second lowest SINAD we have measured of any phono stage:
best digital phono preamp review 2021.png


Side note: does the red bar look taller to you all than the green one to the left of it with the same height? It does to me.

Testing for overflow shows very low headroom which is something that we see in digital phono stages:

NAD PP 4 Measurements THD+N vs Level.png


Fortunately tonality should be good given the nice RIAA implementation:
NAD PP 4 Frequency Response Measurements Moving Magnet.png


Yes, it is a hair rough but overall tonality should be fine.

Conclusions
It would have been nice to have an ADC with phono stage built-in. NAD gets the packaging right but good bit of performance is left on the table. Granted the LP format itself doesn't need high performance digitizer given its high grove noise and such. But it may need higher overload margin. And for line input, we surely want something cleaner even at $200 price point.

Sadly I can't recommend the NAD PP 4. I liked it going in, didn't coming out. You are better off buying a budget phono stage and an audio interface for digitization.

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As always, questions, comments, recommendations, etc. are welcome.

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Side note: does the red bar look taller to you all than the green one to the left of it with the same height? It does to me.
The red bar both breaks the pattern of the green bars sloping down and it has a warning color causing it to stand out.
 
In your Phono Preamp SINAD bar chart, what is the entry at the far right labeled "Chrod huel" ?? Is that a Lirpa phono stage?
 
So, I imagine that at NAD, the marketing department will ask for a product with a great feature set and use-case. The target audience is definitely the current and future generation of HiFi enthousiasts and they nail the concepts in my opinion. The technical development team will still only work on paper or in CAD, selecting name brand components and tieing it together in what looks to be a proper design. Next; the actual fabrication is done for the lowest price available and software will be outsourced. Than Quality Control turns it on, verifies that it works roughly as intended, sound comes out and BAM! Batch approved. Roll out!
 
Ironically despite the poor distortion spec and phase shift both those parameters are probably worse on every cartridge plugged into it and every LP that may be played using it.
It does have a proper high pass filter too, which will make it better, in practical terms, than any phono stage without one.
 
I do get concerned when products are compared to a standard somewhat higher than is appropriate to their application. Phono stages are a case in point.
 
I do get concerned when products are compared to a standard somewhat higher than is appropriate to their application. Phono stages are a case in point.
But the line in is not any better than the phono stage, they both sucks, whether you compare to ADCS or to phono stages.
 
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Side note: does the red bar look taller to you all than the green one to the left of it with the same height? It does to me.
Scientifically speaking, the RGB for red is 255,0,0 whereas for green it is 0, 255,0. Therefore computers, regardless of operating system or code, being binary in nature, always rank red higher than any other color. This “bias” is showing in the graph and is not a visual trick of the brain.
 
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Thanks Amir. I hope my NAD PP2 is better than this. At the price point, you'd be better off with an Art DJ and a Focusrite Scarlett 2i2. seems Parks Puffin reigns in the phono pre with ADC category.
 
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