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Review and Measurements of Hypex NC400 DIY Amp

restorer-john

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My almost 100% silent PC is in a cabinet, which does make it silent, and I have a pair of 200mm Noctua fans venting the cabinet. I have a cheapo voltage regulator dialing a power supply down to provide enough airflow without generating any noise. I had thought about doing something similar for several shelves in my stereo rack...
Agreed. My audio PC is definitely quieter than my amp's transformer noise.
 

maty

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maty

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The S / N ratio is good in absolute scale and is excellent for class D value of 6 dB, and the dynamics climbs to the ceiling of 108 dB.
It must be 86 dB at 1 watt. OK in a cheap SS amplifier but hot here! € 4,000 or $ 4,000.
 
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FrantzM

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amirm

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amirm

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What happens after 20 watts? Why? :(
Really bad. Have seen this in some other amplifiers (schiit headphone amps come to mind). There are clearly two sources of distortion there...
 
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What make you think so? Specifications look pretty terrible.
not so bad ... for less than 150$ (in coax or usb of course)
Specification
Type: Full digital decoding amplifier
Input port: USB/AUX/3.5mm Coaxial and Optical 1/Bluetooth/Optical 2
Output Port: Amplifier output port/3.5mm Headphone port/Subwoofer
Voltage: 24V
Output power:80W x 2
SNR(Signal to Noise): 90dB
THD+N: 0.04%
Output consumption: 50W
Standby power:0.8w
EQ adjustment: 7
Headphone output(32ohm): [email protected]=0.04%
USB sampling rate: 24bit 96kHz
Optical sampling rate:44.1kHz-192kHz
Coaxial sampling rate:44.1kHz-192kHz
Treble adjustment range: ±8db,Bass adjustment range:±8db
Net Weight: 572g
Gross Weight:1585g
Machine Size: 172*51*85mm
 

pos

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Certainly not ncore territory, and not hifi either.
90dB of SNR for a 80W amp, that will most probably directly translate into around 770uV of residual noise, compared to 27uV for a nc400.
That is a 29dB difference, meaning noise will be readily audible on any decently sensitive loudspeaker.
 

restorer-john

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not so bad ... for less than 150$ (in coax or usb of course)
Specification
Type: Full digital decoding amplifier
Input port: USB/AUX/3.5mm Coaxial and Optical 1/Bluetooth/Optical 2
Output Port: Amplifier output port/3.5mm Headphone port/Subwoofer
Voltage: 24V
Output power:80W x 2
SNR(Signal to Noise): 90dB
THD+N: 0.04%
Output consumption: 50W
Standby power:0.8w
EQ adjustment: 7
Headphone output(32ohm): [email protected]=0.04%
USB sampling rate: 24bit 96kHz
Optical sampling rate:44.1kHz-192kHz
Coaxial sampling rate:44.1kHz-192kHz
Treble adjustment range: ±8db,Bass adjustment range:±8db
Net Weight: 572g
Gross Weight:1585g
Machine Size: 172*51*85mm
Oh come on, this thing is just another toy and a waste of time to review it. The 'specifications' are a joke and have a look at the reviews for failures and issues- there are an awful lot.
 
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Oh come on, this thing is just another toy and a waste of time to review it. The 'specifications' are a joke and have a look at the reviews for failures and issues- there are an awful lot.
Of course, it not play on the same field than Hypex, and I'm not a specs expert, but I still think that is interesting to review other technologies (here full digital instead half digital in hypex) to check contributions and failures of each devices. Anyway it's just a proposal, and audiophile often like toys :) For your information the AD18 use similar Texas amplifier chip than Marantz and Lyngdorf ...
 

restorer-john

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Of course, it not play on the same field than Hypex, and I'm not a specs expert, but I still think that is interesting to review other technologies
Absolutely look at lots of other gear.

I agree, it's all fun, but advancements of the state of the art are always more interesting than regression.
 

Ron Texas

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Some random thoughts, and forgive me if they have already been covered. Hypex recommends one SMPS600 per NC400 module to reach rated power of 400 @ 4 ohms. Amir's guess that the single power supply limits power output is
I don't remember anymore. But here are the sweep parameters for the power graph:

View attachment 20229

As you see I had to go up to 2 volt to get past clipping point.

The 5 minute run was at 1.9 volt input to generate 335 watts at 4 ohms.
According to Nord it takes 2.35 V to reach 200 watts at 8 Ohms with a 26 db voltage gain module. The difference is likely because the NC400 was not reaching its full power output due to the power supply being too small. At any rate most DAC's would need a preamp to reach full power with anything other than the 125 WPC @ 8 ohms model.

On another topic, Nord has informed me they have a US service center just in case something goes wrong. The MiniDSP crossover with Dirac LIve operates at an internal frequency of 48 khz, so it would be no better than the XLS 1502 in that regard. I am on my way home and have listened to live music every evening this week.
 

AnalogSteph

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A commercial amplifier with the Hypex NC500 + HDAM buffer, Marantz PM KI Ruby:

[Polish] https://audio.com.pl/testy/stereo/odtwarzacz-cd-wzmacniacz/3021-marantz-sa-pm-ki-ruby

to English: https://translate.google.com/translate?sl=pl&tl=en&u=https://audio.com.pl/testy/stereo/odtwarzacz-cd-wzmacniacz/3021-marantz-sa-pm-ki-ruby

Remember, with HDAM SA3 and SA2.



What happens after 20 watts? Why? :(
Looks like the kind of distortion you get with a "Class A but can also run AB" kind of output stage, i.e. an overbiased AB. Since this appears to be purely tied to voltage levels, indicating a source preceding the power amp, I'd guess one of the HDAMs is breaking a sweat. I never got what the fuss was all about with those mediocre things anyway. I have yet to see one discrete folded cascode opamp that performs truly well. (Never had much luck with them in simulation either. I guess this topology lends itself more to integration, as prominent examples like the AD797 show.)

Unless a schematic is available, some reverse engineering would be needed to determine what the problem is. Input level for a 26 dB amp module at 20W/8R is only 0.6 Vrms and change, or roughly 1 mA rms (~3 mA p-p) into a 600 ohm impedance - hardly an extreme amount of current.
 
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