NAD M28 Seven Channel Power Amplifier Review

[Krobar]

I don't think it's expensive for what you get. 7 very high performance amplifiers in a beautifully finished cabinet by a major manufacturer. If I needed 7 channels of top performing Class D, I'd put it on the list for sure. In Australia, it's MSRP is $7999. Almost good value.

@amirm Did you notice any differences between the various channels with repsect to their placement? Did you employ left and right channels at opposite ends of the unit or side by side? I presume they are identical vertical placement in the chassis. Is there any interaction between adjacent channels?



The M28 delivers more power at lower distortion than the reference design according to your tests into both 4 and 8 ohm loads. The reference design may hit a lower distortion but hits a Po wall well before the NAD. NAD rate the amplifier 20-20KHz at less than or equal to 0.003% THD (and CCIF IMD, DIM 100) and its rated power output and THD appear to correspond perfectly.

Gotta agree. I have an Apollon and a Nord but this looks nicer built and when you consider 20% discount should be easy to obtain it is a good deal IMHO.

 

[Billy Budapest]

Whew! My M27 lives on! Thanks for the review.

Right. No appreciable difference in performance between the two.

 

[Billy Budapest]

Gotta agree. I have an Apollon and a Nord but this looks nicer built and when you consider 20% discount should be easy to obtain it is a good deal IMHO.

For US and Canadian purchasers, do the Apollon and Nord units have the requisite UL, FCC, and/or CSA certifications?

 

[EchoChamber]

I find it intriguing that the Purifi amplifier module performs so differently from other implementations.

 

[Doodski]

For US and Canadian purchasers, do the Apollon and Nord units have the requisite UL, FCC, and/or CSA certifications?

It appears that pic @ post #92 indicates UL and CSA standards are met. Exactly what those standards are and at at what level are they implied is a question. Are the modules UL and CSA approved before NAD worked them.

 

[RichB]

Are there wide-band measurements taken like the 19 an 20 kHz intermodulation measured on the AHB2:

Is there out-of-band switching noise and were measurements taken with AES filter in place?

- Rich

 

[PuX]

Really curious about the new NAD C 298 power amp.

Seems to be based on same Purify technology (not sure which exact module) and has more than enough power for home use (185 Watts per channel). Price is more reasonable since it has only 2 channels ($2000 MSRP, still kind of expensive). As long as NAD does not spoil it by their tweaks and optimisations, it might be good.

https://nadelectronics.com/nad-intros-c-298-power-amplifier-with-purifi-eigentakt-amplification/

 

[WhiteCoatGeek]

ATI's AT527NC 200W x 7 is $800 cheaper, measures marginally better and comes with 4 yrs of additional warranty. Apart from better looking, I am not sure how is M28 better than ATI???

 

[Vasr]

ATI's AT527NC 200W x 7 is $800 cheaper, measures marginally better and comes with 4 yrs of additional warranty. Apart from better looking, I am not sure how is M28 better than ATI???

Asked the same question with no answers. The ATI using older models does not seem to have as wide a bandwidth FR like the Purify modules. It uses a linear power supply rather than a switched power supply I believe which may have implications on heat and efficiency.

I cannot understand the free pass this unit is getting based on its looks and use of newer class D modules. From my perspective, the NAD engineering has under-delivered on the potential with mediocre integration effort than capitalize on it. Noise due to ground loops and improper grounding design as proposed here should make it unacceptable for the price. It is like a DAC under-performing the chip spec by a non-trivial amount by poor engineering. Denons get dissed if the current generation did not measure as good as the previous generation but not this one.

From a purely objective engineering perspective and for the price, I would consider this as "a swing and a miss" (there should be a panther for this which would acknowledge a laudable attempt but also the shortfall) with a recommendation to wait for a v2 instead.

This is the kind of thing that gives more ammunition to that conspiracy nutcase at SBAF. He might be adding a bullet now on how Amir's secret arrangement with NAD to promote poor products over those of better measuring competitors with whom he has a beef.

I have nothing against NAD other than as someone who had NAD products before and expect much better engineering not just skinning.

 

[PeteL]

ATI's AT527NC 200W x 7 is $800 cheaper, measures marginally better and comes with 4 yrs of additional warranty. Apart from better looking, I am not sure how is M28 better than ATI???

The measurments I saw are not very torough, not enough for me to assess that it performs marginally better, maybe. In any case, Purifi modules are more expensive than ncore, there is not based on measurments enough evidence that they are better, maybe we should ask Putzey why and how Purifi is his high end product. And yes... ATI's are uglier, this matter to me, I'm weird like that I know, but all accounted for I believe they are priced what they should be. I know I didn't answer to your question, how it is better? I answer the question on why in my opinion it should cost more.
edit: he does try to explain it here: It's for some of us that feels that ther could theoretically have some hidden things that don't necessaily show with a standard sets of measurments. I'm not saying not measurable, just not showing here. Amir also said something about stability of the design (for the ref design) where he didn't put a number on.
https://purifi-audio.com/wp-content/uploads/2020/06/Purifi-news-by-Jez-Ford-SoundImage-magazine-.pdf

 

[Daniel0]

I cannot understand the free pass this unit is getting based on its looks and use of newer class D modules. From my perspective, the NAD engineering has under-delivered on the potential with mediocre integration effort than capitalize on it.

I don’t understand that either. The NADs seem to get overly positive responses in comparison to the heated discussions in various AVR reviews here.

From a purely objective engineering perspective and for the price, I would consider this as "a swing and a miss" (there should be a panther for this which would acknowledge a laudable attempt but also the shortfall) with a recommendation to wait for a v2 instead.

If NAD would have designed the amp boards themselves that would be pretty good.
But they took the excellent purifi modules and degraded their performance a fair bit.
Their marketing relies heavily on them as well without delivering on their actual performance.

Maybe the conclusion to the reviews should consider the actual performance of the module if it was reviewed before with better results.

 

[PeteL]

I don’t understand that either. The NADs seem to get overly positive responses in comparison to the heated discussions in various AVR reviews here.

Maybe we should get more multi channels amp, to review, but so far it's the second best "performing" multi channel amp here, only beaten by an other NAD amp. Overly positive, maybe, but is there something better out there? If it haven't been found, it's hard to criticise, If it has been done better, let's look at it and assess that it underperforms.

 

[amirm]

Is there out-of-band switching noise and were measurements taken with AES filter in place?

I use a wideband AES filter for all class D amps. It has flat response to 40 kHz and bandwidth is about 250 kHz. Without it, the ultrasonic switching noise confused the THD+N analyzer in AP.

 

[Casey Leedom]

@amirm, do you think that Erik at Gig Harbor Audio could help facilitate a connection to NAD Engineering? It would be awesome to see a better outcome than this for $5K ... I’m going to accept delivery of it because I did order it and I don’t want to leave Erik holding the bag, but I sort of have to agree with others that it’s not clear this deserves a recommendation at this price for having essentially short-changed the Purifi 1ET400A implementation ...

Casey

 

[Daniel0]

Overly positive, maybe, but is there something better out there?

It really depends how many devices you want, there are plenty of multichannel hypex ncore amps out there and you have to try really hard to degrade their performance.
If you want higher end performance that actually delivers then you only have the choice of smaller companies like nord, march etc. that offer 2-channel or 3-channel amps based on NC500, NC1200 or Purifi.
I would want the better performing and cheaper devices instead of a single box doing worse on both ends.

If you consider the advantages big companies have compared to small ones like nord,march etc. the result is even more depressing.

 

[Billy Budapest]

It appears that pic @ post #92 indicates UL and CSA standards are met. Exactly what those standards are and at at what level are they implied is a question. Are the modules UL and CSA approved before NAD worked them.

I’m talking about the Nord and Apollon implementations. It’s not the modules that would be tested for UL and FCC certification, it’s the finished product sold in commerce to consumers.

 

[PeteL]

you have to try really hard to degrade their performance.

The fact remain that they haven't done a 7 channel version, of course if you are just connecting the reference design together, you are less likely to degrade performance. But this require more power, there are more stuff in the box, a more complex power distribution, everything being closer together. they made a choice that 2 dB more gain was desirable for the use case of their target audience, and did so while keeping noise and distortion below audible level. Look at the amp chart, Nord's implementation of NC500 loose a 2 dB Sinad over this, to me this is a bigger fail. Nord Mono Block scores top marks. There are reason for this. The question should not be IF a multichannel amp like this would perform below the theoretical limit of the modules, It's how much below is acceptable. Again we would need to compare with other 7 channels amp to see if they did well. Even if we forget about the 7 channel things, we still have two NAD amps in the top 10 SINAD of every amps reviewed here. The chosen class D module is not everything.

 

[Vasr]

I don’t understand that either. The NADs seem to get overly positive responses in comparison to the heated discussions in various AVR reviews here.

I don't think it is a NAD brand-affinity thing. Most of the recent NAD traditional products (NAD AVRs for example) got trashed in the reviews and comments while there were obvious NAD fans that came to its defenses which happens in any brand review.

I think this is more of a Class D and latest technology affinity thing. Class D is in some sense the poster child for a measurement based approach and implicitly a favored child because of it perhaps. If another brand does a better implementation of Purifi and/or for a lower cost, I think NAD would be forgotten in a jiffy.

If NAD would have designed the amp boards themselves that would be pretty good.
But they took the excellent purifi modules and degraded their performance a fair bit.

I agree. This is what the problem is in an objective evaluation geared towards engineering standards.

Maybe we should get more multi channels amp, to review, but so far it's the second best "performing" multi channel amp here, only beaten by an other NAD amp. Overly positive, maybe, but is there something better out there? If it haven't been found, it's hard to criticise, If it has been done better, let's look at it and assess that it underperforms.

Yes and no. I think Amir has posted before that ASR does not do relative grading. The review itself is, in theory, an objective evaluation of the DUT with respect to engineering standards that it should strive towards (and this is what I have always liked about this site). It does not depend on whether something else better is out there or not for the recommendations. With just that in mind, I think the NAD unit is a swing and miss at best.

It was my impression that objective criterion like avoiding engineering lapses (bad grounding for example), not meeting full potential of components used (DAC chips or Class D module, etc), were things that weighed in on the subjective part of the review while also considering price and uniqueness as a category (multi-channel amp is not a unique enough category). This is where I am disappointed.

You have a valid point of comparing other available products as a consumer wishing to purchase. This is where comparison to ATI etc, becomes relevant and should have common set of measurements to compare. I tried comparing it to the 2-channel ATI amp (but modular where the same chassis is designed to accommodate multiple modules) measured here earlier. Nothing compelling on the NAD (except wide-band FR) despite using a more advanced amp module. We don't have measurements like the multi-tone IMD for the NAD to compare against the earlier ATI measurements, so it becomes difficult to compare all aspects and see if there are clear wins.

As a consumer, I don't care if it has the latest Class D technology or not but whether it has the price/performance I need, of course and that includes the universe of all multi-channel amps not just Class D based ones.

 

[Billy Budapest]

Really curious about the new NAD C 298 power amp.

Seems to be based on same Purify technology (not sure which exact module) and has more than enough power for home use (185 Watts per channel). Price is more reasonable since it has only 2 channels ($2000 MSRP, still kind of expensive). As long as NAD does not spoil it by their tweaks and optimisations, it might be good.

https://nadelectronics.com/nad-intros-c-298-power-amplifier-with-purifi-eigentakt-amplification/

Agreed. Would love to see this tested.

 

[PeteL]

As a consumer, I don't care if it has the latest Class D technology or not but whether it has the price/performance I need, of course and that includes the universe of all multi-channel amps not just Class D based ones.

I agree with this. In my opinion it does score high in the price/performance of any amps, that was my point. I find it hard to fault a amp that measures in the top 10 since the introduction of this site. Assumptions of bad grounding or engineering lapses, I think are absolutes and electronic design is not about absolute. It's not a binary pass or fail, good grounding or bad grounding, it's a scale from worst to better to best, and where is this amp on this scale.