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Review and Measurements of NAD M27 PWR Amp

amirm

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#1
This is a review and detailed measurements of the NAD M27 7-channel surround audio amplifier. It is on kind loan from a member. Seems like the M27 came out back in 2014 and costs US $4,400.

The M27 has the same design language as the excellent M17 Home Theater Processor (looks only):

NAD M27 Seven-Channel Amplifier Audio Review.jpg

The enclosure, especially the top surfaces, oozes quality and luxury in the way that many high-end audio companies fail at. And the looks are actually functional with ample ventilation holes for proper cooling. I will do a teardown later to show this in more detail.

One strange bit of functionality is that the NAD logo lights up orange but goes off when the amplifier is turned on using the touch button on top. This is backwards but fits the functionality for home theater use in darkened room.

The rear panel takes the high quality look of the front and top to the back:

NAD M27 Seven-Channel Amplifier Back Panel Audio Review.jpg

Everything from XLR connectors to speaker terminals is stout and feels solid.

In use, the amplifier when driven in two channel mode, never came remotely close to complaining, shutting down, etc. which I frequently see in AVRs.

Heat dissipation at first is very modest but after half hour of use, the idle power consumption of the rest of the unused channels served to warm up the top. No worries though as it was not remotely "hot." This is due to use of switching power supply (single one powering all the channels) and class D amplifiers based on design from Hypex nCore series. The actual implementation is custom which I will show in teardown.

For my testing, I focused on XLR input only. I hope if you buy an amplifier of this class, that is the connection you use.

Power Amplifier Audio Measurements
As usual, we start with our dashboard, driving two channels into 4 ohm at 5 watts:
NAD M27 Seven-Channel Amplifier Audio Measurements.png


Ah, what a relief it is to see excellent SINAD (signal over noise and distortion) in home theater space after testing so many subpar amplifiers in AVRs. Distortion products are around -110 dB. Ironically, this is far better than the processor and AVR DACs we have tested. In 2-channel world, our desktop class are usually way ahead of amplifiers but not in home theater. So far anyway.

The very nice showing in noise and distortion puts the M27 amplifier near top of the class:
Best Audio Amplifiers Reviewed and Measured.png


Spectrum of 1 kHz FFT shows the typical switching frequency in 400+ kHz:

NAD M27 Seven-Channel Amplifier FFT Audio Measurements.png


Here is the frequency response:

NAD M27 Seven-Channel Amplifier Frequency Response Audio Measurements.png


There is a kink in there around 50 kHz but seeing how it is way out there as far as audiblity, it should be OK. May differ though with a real speaker load.

Crosstalk is very good:
NAD M27 Seven-Channel Amplifier Crosstalk Audio Measurements.png


Dynamic range at around rated power is excellent (better than 20 bits in digital terms):

NAD M27 Seven-Channel Amplifier SNR Audio Measurements.png


Even at rated power you have 105 dB or 17.5 bits.

Most important test is THD+N (distortion+noise) relative to power level as we increase input. Here it is at 4 ohm:

NAD M27 Seven-Channel Amplifier Power into 4 ohm Audio Measurements.png


Wow, this is one powerful beast in stereo mode. Courtesy of a power supply that is designed to feed 7 channels, it is not a bottleneck in 2-channel mode allowing these class d modules to sing. And sing loud!

8 Ohm output is also quite good:

NAD M27 Seven-Channel Amplifier Power into 8 ohm Audio Measurements.png


Of course in neither case we are able to match the state-of-the-art 2-channel amplifiers from likes of Benchmark or Purifi. But what is there at -90 dB or better should be quite excellent.

Peak power as you can imagine, is even higher:
NAD M27 Seven-Channel AmplifierPeak Power Audio Measurements.png


Here is a refined version of a recent test: I sweep for power using different frequencies from 20 kHz on down to just 20 Hz. Test bandwidth is 45 kHz so that it allows enough harmonics to be included in the test but not too much that it just shows ultrasonic noise-shaping and such:

NAD M27 Seven-Channel Amplifier Power into 4 ohm versus frequency Audio Measurements.png


As expected, at low frequencies we have lowest distortion (lowest graphs) but we clip due to much larger power demand of these "slow" waves.

Conclusions
The NAD M27 surround power amplifier has exceptional looks and build quality. It is beautiful to look at. That beauty runs way deep into its veins, producing lots of power in a class-leading way. Efficiency of class-d power amplifier and switching power supplies serve to keep the unit quite cool for its power rating and number of channels. Great attention has gone into heat management and signal flow -- something I don't normally see in DIY hypex ncore builds.

Yes, at US $4,400 it is not cheap but you are getting 7 channels of amplifications. That is roughly $630/channel which is actually quite competitive.

I am probably drunk but from good measurements and great looks of NAD M27 but I am happy to give it one of my highest recommendations.

If you have a home theater and want a gorgeous, powerful and performant multi-channel amplifier, your search is over. Get the M27 and worry about money for food later.

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

It has been raining and raining hard. Starting to get to me. I need to go to a steak and lobster dinner to drown out m sorrows. As usual, my appetite is ahead of what money I want to spend so need your donations: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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#2
Nice to see that, even big names can build good units.
Nowadays most of the big companys ususally just making trash and try to sell with the brandname.
 

Matias

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#3
Here is a refined version of a recent test: I sweep for power using different frequencies from 20 kHz on down to just 20 Hz. Test bandwidth is 45 kHz so that it allows enough harmonics to be included in the test but not too much that it just shows ultrasonic noise-shaping and such:
This is great! I only wish the other amplifier reviews had this chart too. Thanks!

nad m27-inside.jpg
 

rajapruk

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#4
”Great attention has gone into heat management and signal flow -- something I don't normally see in DIY hypex ncore builds.”

Can you please elaborate on the signal flow part. I do not get what you mean. Maybe language barrier for me here.
I have nc400 builds myself, with some attention to heat management.
 

audimus

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#5
NAD like other companies of their generation have been good at building amps. Good to see the tradition continue into Class D without growing pains.

It is when these companies get into digital processing, that they falter and stumble.
 

Vovgan

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#7
Does anyone have a hunch whether this NAD amp would go well with OPPO UDP-205 feeding it with multi-channel analog inputs?
 

speedy

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#10
Does anyone have a hunch whether this NAD amp would go well with OPPO UDP-205 feeding it with multi-channel analog inputs?
Sounds like a great pairing to me.

Pretty good. At almost 1/3 the price, Monoprice has a 7ch amp, Audioholics measurements, not far behind.
It would be interesting to see how the Monolith 7 would test since I think Gene actually tested the Monolith 2.
 

maty

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#11
The new modules, by the power, must be Hypex NC1200, maybe with some NAD mod.

Hypex-NC1200-specs-power.png
 

amirm

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#12
The new modules, by the power, must be Hypex NC1200, maybe with some NAD mod.
They are completely different looking. From what I can tell, they are used the design but did their own implementation.
 

MZKM

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#13
Sounds like a great pairing to me.


It would be interesting to see how the Monolith 7 would test since I think Gene actually tested the Monolith 2.
He states that the 7ch has the larger power supply to allow the same wattage. However, the SINAD may degrade, so yes, the full 7ch measurements would be nice to see.
 

Matias

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#14
Could be just 7x NC500 OEM with their 7x customs buffer board and a single SMPS feeding them all, although that SMPS does not look like SMPS3k or SMPS1200.
 

GrimSurfer

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#15
It pays to play.

Anyone expecting to get excellence in an AVR (DAC, preamp, amp, room correction) for $2k is likely dreaming. But, it seems one can get excellence in amplification for a few grand. $5k is a little on the high side but follows a certain scale.

What scale am I talking about? If you use Benchmark as (ahem) the benchmark, around $1500/ch. Bryston and Mc, slightly higher, though I would caveat these last two as not quite at the same level as Bryston and, quite possibly, as much a fashion statement as an audio one.
 

audimus

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#16
Pretty good.

At almost 1/3 the price, Monoprice has a 7ch amp, Audioholics measurements, not far behind.
One more factor in considering these amps and prices. I see them as long term buys well past the warranty period because they stay relevant and keep working for longer. So, amortized over time, they are actually much more sensible than most front-ends.

For multi-channel amps, I do strongly favor designs with clean independent replaceable channel modules and brands that have a decent enough sales for a long enough period to be able to fix a channel with factory parts or salvaged parts from shops that specialize in that brand.

Just like cars... :)
 

audimus

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#19
It pays to play.

Anyone expecting to get excellence in an AVR (DAC, preamp, amp, room correction) for $2k is likely dreaming. But, it seems one can get excellence in amplification for a few grand. $5k is a little on the high side but follows a certain scale.

What scale am I talking about? If you use Benchmark as (ahem) the benchmark, around $1500/ch. Bryston and Mc, slightly higher, though I would caveat these last two as not quite at the same level as Bryston and, quite possibly, as much a fashion statement as an audio one.
I agree that this is a bit overpriced at $5k.

With volumes, it is theoretically possible to get good AVRs. The intrinsic problem with AVRs is basically too much crammed into one single box with all the compromises it entails.

The boutique names have to have huge margins to stay in business and they cannot compete with mass market brands for volume.
 

GrimSurfer

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#20
From the corporate perspective, sales volume + profitability = bonus.

I do, however, strongly agree with your thesis about the intrinsic weakness of AVRs. Added to that is the low likelihood that one company will be good at everything (DAC, preamp, amp, equalization, etc).

Discrete components offer the best opportunity to achieve high performance... but one must pay to play.
 
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