This is a review and detailed measurements of the Nord One Hypex NC500 class-D module based power (speaker) amplifier. It is on kind loan from a member who recently purchased it. Nord is a British company so lists the cost of the Nord One as £ 979 or US $1,250 as of this writing. For that cost you get a pair of NC500 class-D modules from Hypex with dual PS1200 power supplies. I *think* this cost includes the stock input "buffer" (amplifier) from Hypex. You also have a choice of fancier, audiophile-type input buffer.The Nord One comes in a very large enclosure (full 19 inch rack width):A hard push button turns the unit on and off. Even with overdriving the unit, I could not get it to go into protection mode so not sure if such a feature is there or not.The back panel has the bare minimum plus trigger sockets:The unit as it came had an issue. Can you spot it?Look at the right channel: the red cable is connected to black terminal instead of red. So the two channels were out of phase from each other. I can just imagine someone buying this and raving about soundstage and such, only to realize that it is a defect, not a feature.Anyway, I fixed it for the measurements you are about to see.The speaker terminals are massive by the way.While we are looking inside, here is what it looks like (pardon the mobile phone picture):Not a whole lot in there as all the heavy lifting is done by Hypex in producing the switching power supplies, the NC500 amplifier modules and an "input buffer" board which seemingly does more. Main power is routed through it rather than directly to the amplifier modules. Speaker output also goes through it.The large enclosure allows the components to be easily laid out. Wiring is generally neat and is better than most non-skilled people could do. It seems like good value to me for all the functionality that is in there and hand assembly of the unit.As usual, we start with our 5 watt output into 4 ohm load for the dashboard:I was a bit unhappy about the channel in blue which seemed to dance around with those extra spikes. The levels are low but not nice engineering.Overall THD+N as expressed with SINAD is in very good category:At 96, it is well above our geometric mean of all the amplifiers tested so far (80). It does lose by a big margin compared to the NC400 though which ironically was a DIY build with a single power supply.Let's see what the power output looks like relative to distortion:I worked hard to get the distortion as low as I could as Hypex data is slightly better than this. I realized that when the unit is dead cold, it performs a bit better. I suspect Hypex has tested the amp some other way than with that eval input buffer board as distortion seems to set it very early in my testing at around 2 watts whereas Hypex doesn't show this effect:Overall power versus distortion curve though does match what they show with that increasing distortion from 5 to 30 watts and then settling down to a lower number. It is unfortunately to see some non-linearity in that range where a lot of listening will be done.Anyway, the good news is that the dual power supplies do their job, helping the NC500 amplifiers to produce copious amount of power to the tune of 445 watts. Combine this with excellent signal to noise ratio and you have a lot of clean power:Frequency Response is uneventful:By the way the above measurements were made without any AES-17 filter. I was asked to evaluate this amp with and without it so I thought I show that in the power measurements at 8 ohm:The graphs with and without AES-17 filters are essentially the same. Below 1 watt, the output level is low enough that the analyzer gets a bit confused with the ultrasonic noise and glitches up and down a bit. So no, AES-17 filter (with 40 kHz flat response) that I use do not give any advantage to class-D amps.Speaking of ultrasonics, here is the output without an AES-17 filter:The switching noise is very high at just -12 dB below signal level. Would have liked to see this lower. The Nord One has no CE mark so would be interesting to see if additional filtering would have been necessary to pass certification. Of course it is not audible so it is OK in that regard.I was surprised that there was less intermodulation distortion at high frequencies than our best measured yet Benchmark AHB2:I will have to double check to make sure the Benchmark was also tested at 5 watts. There is however harmonic distortion that is much higher than the Benchmark starting at 35 kHz.We can see that in this graph of THD+N versus Frequency at a few different power levels:The red graph is at lowest power (probably less than 1 watt) and the pink is at max (440 watts). The rise in distortion above 1 kHz is too steep in my liking. In that regard, the 1 kHz measurements we usually perform are the best case scenario.I went into this review expecting better results than I achieved. Despite higher designation, the NC500 seems to be a lower performing module than NC400. How much the input buffer board adds to this, is unknown until we test other variations.That aside, you are getting huge amount of clean power here that outdoes all of the bargain amplifiers we have tested so far (switching or not). At nearly 500 watts into 4 ohm, you should have ample power to drive anything from subwoofers to main speakers. The extremely high signal to noise ratio should be silent in use. Price is reasonable assuming shipping is not too expensive and it includes the input buffer.In other words, we have found another power amplifier that I can recommend.----------------------Questions, comments, critique, etc. are welcome.My late grandfather-in-law used to say,To wit, I don't remember if I asked you all to send me money so I can buy a boat and enjoy the beautiful weather we are having. Regardless, send me the money anyway using: https://www.patreon.com/audiosciencereview ), or https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054 ).