MZX Audio PHO-NR1 Phono Stage Review

[welwynnick]

I added the MZX to my phono amp league table, and ignoring the RIAA issue, it compares really well in terms of SNR:

 

[totti1965]

This is a review and detailed measurements of the MZX Audio PHO-NR1 stereo balanced phono preamplifier. It was sent to me by the company and costs 339.000 Hungarian Forint or about USD $1,017.
View attachment 486040
I have taken the top off for reasons mentioned below. The front and back panels are plexiglass while top and bottom are fairly thick machined aluminum, giving the unit a rather solid feel. The sole LED communicates something about the settings which I did not bother to learn. What I did have to learn was how to change the gain setting which required getting inside the unit. Documentation is provided on the dip switches but not how to open the unit. I guessed that the four upper screws might let the upper shell and fortunately, I was right:
View attachment 486058
I really wished the switches were mounted underneath the PCB with a cut out in the case so that you could change them without opening the unit. While the high voltage wires have good sleeves over them, there is still some chance of electrical shock should the owner not unplug the unit.

I had to change the dip switches because the default gain is whopping 72 dB! The input loading is also a very low 1 kHz. Even though the unit is advertised as supporting Moving Coil cartridge support, the lowest gain is 52 dB which in my opinion is too high. Since there was nothing lower, that is how I tested the unit.

A nice Meanwell switching power supply is on the left. Unit can be powered with a linear power supply which based on my testing, is completely unnecessary and may make things worse.

My favorite feature is highlighted in the back:
View attachment 486059

Yes, we have balanced input and outputs which is rare in this category. I like it due to higher immunity it provides for hum and buzz. My testing showed total absence of such which is usually a major chore in testing phono stages.

MZX Audio PHO-NR1 Phono Stage Measurements
Using my standard 5 mv input level showed an output that was 2 volts. This is double of what I typically see and would create an unfair comparison. I lowered that to 2.5 millivolt to compensate for the higher gain:
View attachment 486060

Output spectrum is very clean, devoid of any distortion products. Channel matching/gain is superb as well. Ranking is way up the chart:
View attachment 486061

Frequency response showed a response with fair amount of peaking in bass:
View attachment 486062
I like the high pass filtering but the rise from 30 to 100 Hz could interact with room modes and could cause fair amount of bloat. Or may make a bright speaker more balanced. Somewhat a crapshoot so wished it was not there or so pronounced.

Headroom measurement comparison is difficult since the 52 dB gain is in between what we see in MM (45 dB or so) and MC (60+ dB):
View attachment 486063
Mentally interpreting, it seems fine to me.

What is way beyond fine and falling in state of the art performance is the extremely low distortion:
View attachment 486064

While this would be falling on deaf ears of the LP format itself, it is nevertheless nice to see as a show of engineering prowess.

Conclusions
The PRO-NR1 takes the proper approach in producing a balanced input to output phono stage. Very few companies recognize the importance of this architecture and for that, I commend the company. Overall performance ranks from good to excellent with the exception of low frequency response. As noted, having a high pass filter to reduce rumble is good but that peaking should be better controlled.

I can't recommend the MZX Audio PRO-NR1 because of that filter error. Otherwise, the rest of the design is commendable.
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My technical question regarding the Headroom measurement comparison:

40 dB gain for typical MM Pre amps is a bit more realistic than 45 dB.
Can we say, if the 52 dB gain would be compared with exactly 40 dB gain (Michael Fidler Spartan, Cambridge Duo or the Fosi Audio Box X5 are all nearly exact 40 dB), so 12 dB difference,
that is to say, if we want a true comparison and
with 52 dB the headroom here for 20.0000 Hz Signals is exactly 14 Vrms, that
this would be exactly equal to 56 Vrms in the Michael Fidler Spartan or the Cambridge Duo (Multiplication with 4)?

Or can we even multiply with 16? Every 3 dB less gain we need twice as much headroom in Vrms?

So that 14 Vrms at 20 kHz with 52 dB gain would equal 14 Vrms x16 = 224 Vrms with the typical 40 dB gain Phono Pre Amps? That would be sensationally good!

I suspect the former is the case, but I am not shure.

 

[totti1965]

I added the MZX to my phono amp league table, and ignoring the RIAA issue, it compares really well in terms of SNR:

View attachment 486129

I would say the same thing: every owner of small two-way speakers can only be grateful for the extra 1.5 dB at 40 Hz.
So at least for them: A really great device, golfing Panther.
Room modes, on the other hand, can easily reach 20 dB and must be controlled in other ways anyway.

I think the MZX-Audio PHO-NR1 is quite a remarkable Amp for Record Lovers. Only Michael Fidler can really compete.

 

[raindance]

I think this might work really well with the Audio Technica VM540ML which I found bass light and bright without EQ even with the recommended capacitive loading. The bass boost might be just what it needs if you don't have the ability to EQ. I'm forever recommending this cartridge despite its tendency to brightness because it doesn't have audible IGD (the sound of which I personally cannot stand but many seem not to notice).

I also found its output a bit low so the extra gain wouldn't be a problem either.

Or maybe the gain in the bass would be too subtle to make enough difference. Who knows?

 

[yo!]

To me it looks like the preamp is sounded by default.
Reminds me of some old Accuphase amps back in the days and some others (a Sony Esprit amp when switched *superclear* or so).
This is the chance for audiophile purists to tweak the sound without getting a complex and hear sound signature differences between upper class hifi units. The curve is somehow like a happy abuse of a subwoofer. As long the speakers can manage this and the record player is stable against feedback ...

Sure, nothing what could called good or acceptable when measurements are done, but no deadly sin too IMHO

 

[amirm]

I also re-did the comparison between the two test tracks, and I’m still not convinced that this issue is audible at all.

You have to have a speaker system that can reproduce down that low (peak is around 40 Hz). Research shows threshold of hearing around 0.5 dB when it is broad (low Q). So this should be audible.

I should say that with bookshelf speakers, such a boost can make them sound better at the expense of dynamic range.

 

[orsib]

Interesting topic... According to the Fletcher–Munson equal-loudness curves, human hearing is about 20–30 dB less sensitive between 20–100 Hz than it is between 1–4 kHz, for example. So this 0.5 dB difference really applies around 1 kHz, not at the edges of human hearing. What do you think about that?

By the way, I used a Chord Mojo 2 and HIFIMAN Edition XS headphones for the "subjective" comparison. Using this gear I can't hear a "convincing" difference between the two samples. Of course we should not forget that we are listening to the recording and playback chain instead of the "real thing", so this kind of comparison is not really representing the reality, but still the difference is there (on paper). I don't even attempted to do this comparison using my Fyne Audio F502 speakers driven by a Kinki Studio EX-EM1 amp, because this combo is already quite “bass-heavy,” so there’s no real chance to do such a comparison around 40 Hz.

 

[mzxa]

Using my standard 5 mv input level showed an output that was 2 volts. This is double of what I typically see and would create an unfair comparison. I lowered that to 2.5 millivolt to compensate for the higher gain

IMHO, on the contrary, the excitation signal change makes the measurement incomparable. What is wrong with a 2V output? Many DACs have 4V or even higher output levels. If it's too loud, then the volume knob is there.
Now, the SINAD measurement is definitely noise-limited, and it will be 89dB at the usual 5 mV input signal.

 

[mzxa]

I added the MZX to my phono amp league table, and ignoring the RIAA issue, it compares really well in terms of SNR:

The MM part was only characterized, but these results were written in the MC section. And you can add +6db to SINAD

 

[totti1965]

People into LPs tend to have pure analog paths and absence of EQ. So can't apply the same logic here.

But e. g. Linn digitizes every single note even in their US$ 60,000 ANALOG chains with 192 KHz 24 (?) bit, to make a correction for any pick up. They simply found out 10 years or so ago, that this simply sounds better - and believe me there is definitivly no "digital sound" added.

Imho the "no recommendation" is a bit harsh for a device with such high qualities: Because you may also argue that audiophiles tend to use their BBC LS 3/5a or Quad ESL 57 stuff...
For these speakers a +1.5 dB gain at 40 Hz would simply be nice......

 

[xanalog]

I can't recommend the MZX Audio PRO-NR1 because of that filter error. Otherwise, the rest of the design is commendable.

Thank you for the review, @amirm,

That must have been one tough disapproval decision, regardless of its otherwise excellent design.
I hope that decision was not partially influenced by 'having' to open it for the DIP switches.
I personally swooned over the photo of the internal lay-out and gave it a Happy-Panther vote... price be damned!

 

[NicS]

I’ve used a fully balanced signal path on my turntable for a while now, using the MX VNYL as the phono preamp. I find it curious that the analog fetishists haven’t embraced a balanced signal path in a purely vinyl setup more vigorously.

Amir’s review of the MX VNYL used the single ended inputs. I’m sure a retest of the MX VNYL using the balanced 4 pin mini-XLR input and a power supply better than the one supplied (I bought a used Swagman LPS for this purpose) would test much better than the current assessment.

I think it sounds much better than it did in single ended mode. Though for all the hassle on making up new cables etc, this might be confirmation bias.

 

[solawind]

I also re-did the comparison between the two test tracks, and I’m still not convinced that this issue is audible at all.

By the way, I used a Chord Mojo 2 and HIFIMAN Edition XS headphones for the "subjective" comparison. Using this gear I can't hear a "convincing" difference between the two samples

An easier way to check how it alerts the sound would be to add a 40 hz 1.5db bass shelf in Windows APO / your player EQ or any EQ software and then try enabing and disabling this filter during playback. With momentary changes the difference becomes much more obvious.

 

[DSJR]

I think this might work really well with the Audio Technica VM540ML which I found bass light and bright without EQ even with the recommended capacitive loading. The bass boost might be just what it needs if you don't have the ability to EQ. I'm forever recommending this cartridge despite its tendency to brightness because it doesn't have audible IGD (the sound of which I personally cannot stand but many seem not to notice).

I also found its output a bit low so the extra gain wouldn't be a problem either.

Or maybe the gain in the bass would be too subtle to make enough difference. Who knows?

A little lift at a frequency not usually cut on a vinyl record, may not do what you're suggesting, although I can think of another phono stage that does similar and it adds a very subtle subjective 're-enforcement' to the entire sound-field... Overload doesn't look good to me, although the aforementioned AT model family don't have higher output as I believe the Ortofon 2Ms do.

The price puts me right off bearing in mind the better cheaper stages available now, so for me I'm afraid - Move along, nothing to see or take interest in here and all those dip switches will be a 'golden eared subectivist's dream!'...

 

[solawind]

I would say the same thing: every owner of small two-way speakers can only be grateful for the extra

I expect a $1k phono owner to have good full-range speakers, so there’s no need for such “enhancers.” Maybe i would agree with this statement for a $50 phono. Can’t be considered a hi-fi device anyway, as it alters the sound (if the term “hi-fi” means anything for vinyl).

 

[sceptical1]

Would it be ridiculous for me to think that the designer has no idea that he is manufacturing a strictly MC phono preamp?
High gain MC - 52db and 1k input
Low gain MC - 62db and 100r input
Very low gain MC - 72db and 100r input
Typical specs for a MM cartridge of 47k input and 40db gain do not exist for this preamp. Something weird is going on.
Otherwise flawless performance and only somewhat overpriced for a $100 parts count product.

 

[dtaylo1066]

Looks well made and except for one issue, well designed. $1,200 and having to remove the cover to fiddle with dip switches is a non-starter for me. Why buy this over the Schiit balanced phono which has balanced and SE inputs and outputs and a remote for $399 - $499.

 

[raindance]

Would it be ridiculous for me to think that the designer has no idea that he is manufacturing a strictly MC phono preamp?
High gain MC - 52db and 1k input
Low gain MC - 62db and 100r input
Very low gain MC - 72db and 100r input
Typical specs for a MM cartridge of 47k input and 40db gain do not exist for this preamp. Something weird is going on.
Otherwise flawless performance and only somewhat overpriced for a $100 parts count product.

There are separate DIP switches for MM but it looks like 52dB gain is applied (which I have no problem with because phono is always so much lower than digital sources otherwise).

 

[Sokel]

I would vote excellent for the Würth capacitors alone

The lift down low will probably go unnoticed on older stuff and and could strangely benefit some setups, but nonetheless is a fail.
And it's a strange fail as the engineering in it its solid, shows someone who knows exactly what is doing.

I have a sweet spot for the dark plexi from my days of ASR (the amps, not the site) but I would still prefer a premium alu black enclosure for phono.

Thanks Amir!

 

[DSJR]

Would it be ridiculous for me to think that the designer has no idea that he is manufacturing a strictly MC phono preamp?
High gain MC - 52db and 1k input
Low gain MC - 62db and 100r input
Very low gain MC - 72db and 100r input
Typical specs for a MM cartridge of 47k input and 40db gain do not exist for this preamp. Something weird is going on.
Otherwise flawless performance and only somewhat overpriced for a $100 parts count product.

I would have failed badly at 'business.'

$100 parts count would mean *at least* $1k selling price, arguably plus sales tax/VAT too... Such is the cost burden a small maker has to endure I suspect.


P.S. This box is MC loading, right? 100r is about right for most MC pickups I believe still, in which cased my criticism is largely unfounded I suspect.