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):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: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.As usual, we start with our dashboard, driving two channels into 4 ohm at 5 watts: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:Spectrum of 1 kHz FFT shows the typical switching frequency in 400+ kHz:Here is the frequency response: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:Dynamic range at around rated power is excellent (better than 20 bits in digital terms):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: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: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: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:As expected, at low frequencies we have lowest distortion (lowest graphs) but we clip due to much larger power demand of these "slow" waves.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.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